Metal-organic framework 1

Metal-organic frameworkMetal-Organic Frameworks are crystalline compounds consisting of metal ions or clusters coordinated to oftenrigid organic molecules to form one-, two-, or three-dimensional structures that can be porous. In some cases, thepores are stable to elimination of the guest molecules (often solvents) and can be used for the storage of gases suchas hydrogen and carbon dioxide. Other possible applications of MOFs are in gas purification, in gas separation, incatalysis and as sensors.[1]

Metal-organic framework structureA metal-organic framework (MOF) is composed of two major components: a metal ion or cluster of metal ions andan organic molecule called a linker. The organic units are typically mono-, di-, tri-, or tetravalent ligands.[2] Thechoice of metal and linker has significant effects on the structure and properties of the MOF. For example, themetal's coordination preference influences the size and shape of pores by dictating how many ligands can bind to themetal and in which orientation.

Coordination Polymers and MOFsThere is no consensus in the scientific literature about the definitions of the terms coordination polymer andmetal-organic framework. Some authors suggest definitions based on chemical bonding[3] [4] others propose that theterms coordination polymer and metal-organic framework are synonyms.[5] An IUPAC project was initiated in 2009to address the terminology issues in this area and will deliver its final report in 2012.[6][7] A progress report has beenpublished.[8]

Classification of hybrid materials based on dimensionality [9]

Dimensionality of Inorganic

Dimensionality ofOrganic

0 1 2 3

0 Molecular Complexes Hybrid Inorganic Chains Hybrid Inorganic Layers 3-D InorganicHybrids

1 Chain CoordinationPolymers

Mixed Inorganic-Organic Layers Mixed Inorganic-Organic 3-DFramework

2 Layered CoordinationPolymer

Mixed Inorganic-Organic 3-DFramework

3 3-D CoordinationPolymers

Describing and organizing the complex structures of MOFs can be difficult and confusing. Recently, a system ofnomenclature has been developed to fill this need. Inorganic sections of a MOF, called secondary building units(SBU), can be described by topologies common to several structures. Each topology, also called a net, is assigned asymbol, consisting of three lower-case letters in bold. MOF-5, for example, has a pcu net. The database of netstructures can be found at the Reticular Chemistry Structure Resource [10].[4]

Metal-organic framework 2

Common ligands in MOFs

Common name IUPAC name Chemical formula Structural formula

Bidentate Carboxylics

Oxalic acid ethanedioic acid HOOC-COOH

Malonic acid propanedioic acid HOOC-(CH2)-COOH

Succinic acid butanedioic acid HOOC-(CH2)2-COOH

Glutaric acid pentanedioic acid HOOC-(CH2)3-COOH

Phthalic acid benzene-1,2-dicarboxylic acido-phthalic acid

C6H4(COOH)2

Isophthalic acid benzene-1,3-dicarboxylic acidm-phthalic acid

C6H4(COOH)2

Terephthalic acid benzene-1,4-dicarboxylic acidp-phthalic acid

C6H4(COOH)2

Tridentate Carboxylates

Citric Acid 2-Hydroxy-1,2,3-propanetricarboxylic acid (HOOC)CH2C(OH)(COOH)CH2(COOH)

Trimesic acid benzene-1,3,5-tricarboxylic acid C9H6O6

Azoles

1,2,3-Triazole 1H-1,2,3-triazole C2H3N3

pyrrodiazole 1H-1,2,4-triazole C2H3N3

Other

Squaric acid 3,4-Dihydroxy-3-cyclobutene-1,2-dione C4H2O4

Metal-organic framework 3

Synthesis of MOFsThe study of MOFs developed from the study of zeolites, except for the use of preformed ligands. MOFs and zeolitesare produced almost exclusively by hydrothermal or solvothermal techniques, where crystals are slowly grown froma hot solution. In contrast with zeolites, MOFs are constructed from bridging organic ligands that remain intactthroughout the synthesis.[11] Zeolite synthesis often makes use of a variety of templates, or structure-directingcompounds, and a few examples of templating, particularly by organic anions. These templates are removed (of byoxidation) in the case of the zeolites, whereas in MOFs, the framework is templated by the SBU and the organicligands.[12][13] A templating approach that is useful for MOFs intended for gas storage is the use of metal-bindingsolvents such as N,N-diethylformamide and water. In these cases, metal sites are exposed when the solvent isevacuated, allowing hydrogen to bind at these sites.[14]

Post-synthetic modification of MOFs opens up another dimension of structural possibilities that might not beachieved by conventional synthesis. A great deal of recent work explores covalent modification of the bridgingligands.[15] Of particular interest to MOFs for hydrogen storage are modifications which expose metal sites. This hasbeen demonstrated with post-synthetic coordination of additional metal ions to sites on the bridging ligands,[14][15]

and addition and removal of metal atoms to the metal site.[14][16]

Since ligands in MOFs typically bind reversibly, the slow growth of crystals allows defects to be redissolved,resulting in a material with millimeter-scale crystals and a near-equilibrium defect density. Solvothermal synthesis isuseful for growing crystals suitable to structure determination, because crystals grow over the course of hours todays. However, the use of MOFs as storage materials for consumer products demands an immense scale-up of theirsynthesis. Scale-up of MOFs has not been widely studied, though several groups have demonstrated that microwavescan be used to nucleate MOF crystals rapidly from solution.[17][18] This technique, termed “microwave-assistedsolvothermal synthesis”, is widely used in the zeolite literature,[11] and produces micron-scale crystals in a matter ofseconds to minutes,[17][18] in yields similar to the slow growth methods.A solvent-free synthesis of a range of crystalline MOFs has been described [19] [20]. Usually the metal acetate is andthe organic ligand are ground and mixed with a ball bearing. Cu3(BTC)2 can be quickly synthesised in this way inquantitative yield. In the case of Cu3(BTC)2 the morphology of the solvent free synthesised product was the same asthe industrially made Basolite C300. It is thought that localised melting when the components may assist thereaction. The formation of acetic acid as a by-product in the reactions in the ball mill may also help in the reactionhaving a solvent effect[21] in the ball mill.

Composite MOF materialsAnother approach to increasing adsorption in MOFs is to alter the system in such a way that chemisorption becomespossible. This has been achieved by making a composite material, which contains a MOF and a complex of platinumwith activated carbon. In an effect known as hydrogen spillover, H2 can bind to the platinum surface through adissociative mechanism which cleaves the hydrogen molecule into two hydrogen atoms and enables them to traveldown the activated carbon onto the surface of the MOF. This produced a threefold increase in the room-temperaturestorage capacity of a MOF; however, desorption can take upwards of 12 hours, and reversible desorption issometimes observed for only two cycles.[22][23] The relationship between hydrogen spillover and hydrogen storageproperties in MOFs is not well understood, but further research in this direction may provide inexpensive boosts inhydrogen storage capacity.

Metal-organic framework 4

MOFs for hydrogen storageConsiderable interest has been shown in the development of non-petroleum energy carriers for use in transportation.Hydrogen is an attractive option because it has a high energy content (120 MJ/kg compared to 44 MJ/kg forgasoline), produces clean exhaust product (water vapor without CO2 or NOx), and can be derived from a variety ofprimary energy sources. However, the specific energy of uncompressed hydrogen gas is very low, and considerableattention must be given to denser storage methods if hydrogen is to emerge as a serious option for energy storage.[24]

Proposed forms of reversible hydrogen storage include: compressed gas, cryogenic liquid, adsorption to highsurface-area materials, chemical storage as metal hydrides, and various reactions of liquid fuels high in hydrogencontent (whose products must be collected and recycled after use).[25][26] Of these, compressed and liquid hydrogenare the most mature technologies and are the most suitable for immediate deployment.[26] The United StatesDepartment of Energy (USDOE) projects that with further technological development, adsorptive or chemicalstorage may prove most effective for storage.[25]

Metal Organic Frameworks (MOFs) attract attention as materials for adsorptive hydrogen storage because of theirexceptionally high specific surface areas and chemically tunable structures.[22] MOFs can be thought of as athree-dimensional grid in which the vertices are metal ions or clusters of metal ions that are connected to each otherby organic molecules called linkers. Hydrogen molecules are stored in a MOF by adsorbing to its surface. Comparedto an empty gas cylinder, a MOF-filled gas cylinder can store more gas because of adsorption that takes place on thesurface of MOFs. (Note that wikt:molecular hydrogen adsorbs to the surface, not wikt:atomic hydrogen.)Furthermore, MOFs are free of dead-volume, so there is almost no loss of storage capacity as a result ofspace-blocking by non-accessible volume.[2] Also, MOFs have a fully reversible uptake-and-release behavior: sincethe storage mechanism is based primarily on physisorption, there are no large activation barriers to be overcomewhen liberating the adsorbed hydrogen.[2] The storage capacity of a MOF is limited by the liquid-phase density ofhydrogen because the benefits provided by MOFs can be realized only if the hydrogen is in its gaseous state.[2]

In order to realize the benefits provided, such as adsorption, by MOFs hydrogen cannot be stored in them at densitiesgreater than its liquid-phase density.[2] The extent to which a gas can adsorb to a MOF's surface depends on thetemperature and pressure of the gas. In general, adsorption increases with decreasing temperature and increasingpressure[2] (until a maximum is reached, typically 20-30 bar, after which the adsorption capacity decreases).[22],[2]

However, MOFs to be used for hydrogen storage in automotive fuel cells need to operate efficiently at ambienttemperature and pressures between 1 and 100 bar, as these are the values that are deemed safe for automotiveapplications.[22]

In 2012, the lab led by William A. Goddard III predicted that MOF-210 will have Hydrogen storage capacity of 2.90delivery wt% (1-100 bar) at 298 K and 100 bar. [27]. Also that MOF-200 will have a Hydrogen storage capacity of3.24 delivery wt% (1-100 bar) at 298 K and 100 bar. [27] They also proposed new strategies to obtain higherinteraction with H2. Such strategy consist on metalating the COF with alkaline metals such as Li.[27] Thesecomplexes composed of Li, Na and K bound to benzene ligands (such as 1,3,5-benzenetribenzoate, the ligand used inMOF-177) have been synthesized by Krieck et al. [28] and Goddard showed that the THF is important of theirstability. If the metalation with alkaline is performed in the COFs, Goddard et al. calculated that two MOFs willreach the 2015 DOE target of 5.5 wt % at 298 K: MOF200-Li (6.34 delivery wt%) and MOF200-Na (5.94 6.34delivery wt%) at 100 bar. [27] Other strategies to increase the interaction of MOFs with molecular hydrogen havebeen reviewed recently. [29]

Metal-organic framework 5

US Department of Energy hydrogen storage guidelinesDespite the fact that the US DOE Secretary has questioned the viability of existing hydrogen storage methods, thesearch for high-capacity hydrogen storage materials remains a highly competitive area of research: the race is on todevelop MOFs that can meet all of the targets set by the DOE. The DOE 2015 targets for a hydrogen storage systemare [30] : 1) a capacity of 40 g H2 per L, 2) a refueling time of 10 min or less, 3) a lifetime of 1000 refueling cycles,and 4) an ability to operate within the temperature range 30 to 50 °C. Note that these targets are for the entire storagesystem; therefore, the performance of a storage material must be even higher in order to account for the storagecontainer and, if necessary, a temperature regulating apparatus.[22] MOF-177 currently boasts the hydrogenabsorption record, with a surface area of 4526 m2/g and an excess hydrogen uptake of 1.23 wt% and 32.1 g/L at1 bar and 77 K.[31]

Examples of MOFs for hydrogen storageThe most important challenge for creating hydrogen adsorbents that operate at room temperature is increasing thehydrogen binding energy.[22] Several classes of MOFs have been explored, including carboxylate-based MOFs,heterocyclic azolate-based MOFs, metal-cyanide MOFs, and covalent organic frameworks. Carboxylate-basedMOFs have by far received the most attention in the literature because

1) they are either commercially available or easily synthesized,2) they have high acidity (pKa ≈ 4) allowing for facile in situ deprotonation,3) the metal-carboxylate bond formation is reversible, facilitating the formation of well-ordered crystallineMOFs, and4) the bridging bidentate coordination ability of carboxylate groups favors the high degree of frameworkconnectivity and strong metal-ligand bonds necessary to maintain MOF architecture under the conditionsrequired to evacuate the solvent from the pores.[22]

The most common transition metals employed in carboxylate-based frameworks are Cu2+ or Zn2+. Lighter maingroup metal ions have also been explored. Be12(OH)12(BTB)4, the first successfully synthesized and structurallycharacterized MOF consisting of a light main group metal ion, shows high hydrogen storage capacity, but it is tootoxic to be employed practically.[32] There is considerable effort being put forth in developing MOFs composed ofother light main group metal ions, such as magnesium in Mg4(BDC)3.[22]

The following is a list several MOFs that are considered to have the best properties for hydrogen storage as of May2012 (in order of decreasing hydrogen storage capacity).[22] While each MOF described has its advantages, none ofthese MOFs reach all of the standards set by the USDOE. Therefore, it is not yet known whether materials with highsurface areas, small pores, or di- or trivalent metal clusters produce the most favorable MOFs for hydrogenstorage.[2]

Zn4O(BTE)(BPDC), where BTE3- = 4,4′,4″-[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)]tribenzoate and

BPDC2-=biphenyl-4,4′-dicarboxylate (MOF-210) [33]

Hydrogen storage capacity (at 77 K): 8.6 excess wt% (17.6  total wt%) at 77 K and 80 bar. 44 total g H2/L at 80 barand 77 K. [33]

Hydrogen storage capacity (at 298 K): 2.90 delivery wt% (1-100 bar) at 298 K and 100 bar. [27]

Zn4O(BBC)

2, where BBC3- = 4,4′,4″-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate (MOF-200) [33]

Hydrogen storage capacity (at 77 K): 7.4 excess wt% (16.3  total wt%) at 77 K and 80 bar. 36 total g H2/L at 80 barand 77 K. [33]

Hydrogen storage capacity (at 298 K): 3.24 delivery wt% (1-100 bar) at 298 K and 100 bar. [27]

Zn4O(BTB)

2, where BTB3- = 1,3,5-benzenetribenzoate (MOF-177) [34]

Metal-organic framework 6

Structure: Tetrahedral [Zn4O]6+ units are linked by large, triangular tricarboxylate ligands. Six diamond-shapedchannels (upper) with diameter of 10.8 Å surround a pore containing eclipsed BTB3- moieties (lower).Hydrogen storage capacity: 7.1 wt% at 77 K and 40 bar; 11.4 wt% at 78 bar and 77 K.MOF-177 has larger pores, so hydrogen is compressed within holes rather than adsorbed to the surface. This leads tohigher total gravimetric uptake but lower volumetric storage density compared to MOF-5.[22]

Zn4O(BDC)

3, where BDC2- = 1,4-benzenedicarboxylate (MOF-5) [35]

Structure: Square openings are either 13.8 or 9.2 Å depending on the orientation of the aromatic rings.Hydrogen storage capacity: 7.1 wt% at 77 K and 40 bar ; 10 wt% at 100 bar; volumetric storage density of 66 g/L.MOF-5 has received much attention from theorists because of the partial charges on the MOF surface, which providea means of strengthening the binding hydrogen through dipole-induced intermolecular interactions; however, MOF-5has poor performance at room temperature (9.1 g/L at 100 bar).[22]

Mn3[(Mn

4Cl)

3(BTT)

8]2, where H3BTT = benzene-1,3,5-tris(1H-tetrazole) [36]

Structure: Consists of truncated octahedral cages that share square faces, leading to pores of about 10 Å in diameter.Contains open Mn2+ coordination sites.Hydrogen storage capacity: 60 g/L at 77 K and 90 bar; 12.1 g/L at 90 bar and 298 K.This MOF is the first demonstration of open metal coordination sites increasing strength of hydrogen adsorption,which results in improved performance at 298 K. It has relatively strong metal-hydrogen interactions, attributed to aspin state change upon binding or to a classical Coulombic attraction.[22]

Cu3(BTC)

2(H

2O)

3, where H3BTC = 1,3,5-benzenetricarboxylic acid [37]

Structure: Consists of octahedral cages that share paddlewheel units to define pores of about 9.8 Å in diameter.High hydrogen uptake is attributed to overlapping attractive potentials from multiple copper paddle-wheel units:each Cu(II) center can potentially lose a terminal solvent ligand bound in the axial position, providing an opencoordination site for hydrogen binding.[22]

Structural impacts on hydrogen storage capacityTo date, hydrogen storage in MOFs at room temperature is a battle between maximizing storage capacity andmaintaining reasonable desorption rates, while conserving the integrity of the adsorbent framework (e.g. completelyevacuating pores, preserving the MOF structure, etc.) over many cycles. There are two major strategies governingthe design of MOFs for hydrogen storage:

1) to increase the theoretical storage capacity of the material, and2) to bring the operating conditions closer to ambient temperature and pressure. Rowsell and Yaghi haveidentified several directions to these ends in some of the early papers.[38][39]

Surface area

The general trend in MOFs used for hydrogen storage is that the greater the surface area, the more hydrogen theMOF can store. This is because high surface area materials tend to exhibit increased micropore volume andinherently low bulk density, allowing for more hydrogen adsorption to occur.[22]

Hydrogen adsorption enthalpy

High hydrogen adsorption enthalpy is also important. Theoretical studies have shown that 22-25 kJ/mol interactions are ideal for hydrogen storage at room temperature, as they are strong enough to adsorb H2, but weak enough to allow for quick desorption.[40] The interaction between hydrogen and uncharged organic linkers is not this strong, and so a considerable amount of work has gone into synthesis of MOFs with exposed metal sites, to which hydrogen adsorbs with an enthalpy of 5-10 kJ/mol. Synthetically, this may be achieved by using ligands whose geometries

Metal-organic framework 7

prevent the metal from being fully coordinated, by removing volatile metal-bound solvent molecules over the courseof synthesis, and by post-synthetic impregnation with additional metal cations.[14][36] (C5H5)V(CO)3(H2) andMo(CO)5(H2) are great examples of increased binding energy due to open metal coordination sites;[41] however,their high metal-hydrogen bond dissociation energies result in a tremendous release of heat upon loading withhydrogen, which is not favorable for fuel cells.[22] MOFs, therefore, should avoid orbital interactions that lead tosuch strong metal-hydrogen bonds and employ simple charge-induced dipole interactions, as demonstrated inMn3[(Mn4Cl)3(BTT)8]2.An association energy of 22-25 kJ/mol is typical of charge-induced dipole interactions, and so there is interest in theuse of charged linkers and metals.[22] The metal–hydrogen bond strength is diminished in MOFs, probably due tocharge diffusion, so 2+ and 3+ metal ions are being studied to strengthen this interaction even further. A problemwith this approach is that MOFs with exposed metal surfaces have lower concentrations of linkers; this makes themdifficult to synthesize, as they are prone to framework collapse. This may diminish their useful lifetimes aswell.[14][22] Most common strategies to increase this binding energy for MOFs and molecular hydrogen have beenreviewed.[29]

Sensitivity to air

MOFs are frequently air/moisture-sensitive. In particular, IRMOF-1 degrades in the presence of small amounts ofwater at room temperature. Studies on metal analogues have unravel the ability of metals different than Zn to standhigher water concentrations at high temperatures. [42]

To compensate for this, specially constructed storage containers are required, which can be costly. Strongmetal-ligand bonds, such as in metal-imidazolate, -triazolate, and -pyrazolate frameworks, are known to decrease aMOF's sensitivity to air, reducing the expense of storage.[22]

Pore size

In a microporous material where physisorption and weak van der Waals forces dominate adsorption, the storagedensity is greatly dependent on the size of the pores. Calculations of idealized homogeneous materials, such asgraphitic carbons and carbon nanotubes, predict that a microporous material with 7 Å-wide pores will exhibitmaximum hydrogen uptake at room temperature. At this width, exactly two layers of hydrogen molecules adsorb onopposing surfaces with no space left in between.[22] 10 Å-wide pores are also of ideal size because at this width,exactly three layers of hydrogen can exist with no space in between.[22] (A hydrogen molecule has a bond length of0.74 Å with a van der Waals radius of 1.17 Å for each atom; therefore, its effective van der Waals length is 3.08 Å.)[43]

Structural defects

Structural defects also play an important role in the performance of MOFs. Room-temperature hydrogen uptake viabridged spillover is mainly governed by structural defects, which can have two effects:

1) a partially collapsed framework can block access to pores; thereby reducing hydrogen uptake, and2) lattice defects can create an intricate array of new pores and channels causing increased hydrogenuptake.[44]

Structural defects can also leave metal-containing nodes incompletely coordinated. This enhances the performanceof MOFs used for hydrogen storage by increasing the number of accessible metal centers.[45] Finally, structuraldefects can affect the transport of phonons, which affects the thermal conductivity of the MOF.[46]

Metal-organic framework 8

Hydrogen adsorptionAdsorption is the process of trapping atoms or molecules that are incident on a surface; therefore the adsorptioncapacity of a material increases with its surface area. In three dimensions, the maximum surface area will be obtainedby a structure which is highly porous, such that atoms and molecules can access internal surfaces. This simplequalitative argument suggests that the highly porous metal-organic frameworks (MOFs) should be excellentcandidates for hydrogen storage devices.Adsorption can be broadly classified as being one of two types: physisorption or chemisorption. Physisorption ischaracterized by weak van der Waals interactions, and bond enthalpies typically less than 20 kJ/mol. Chemisorption,alternatively, is defined by stronger covalent and ionic bonds, with bond enthalpies between 250 and 500 kJ/mol. Inboth cases, the adsorbate atoms or molecules (i.e. the particles which adhere to the surface) are attracted to theadsorbent (solid) surface because of the surface energy that results from unoccupied bonding locations at the surface.The degree of orbital overlap then determines if the interactions will be physisorptive or chemisorptive.[47]

Adsorption of molecular hydrogen in MOFs is physisorptive. Since molecular hydrogen only has two electrons,dispersion forces are weak, typically 4-7 kJ/mol, and are only sufficient for adsorption at temperatures below 298K.[22]

The first complete explanation of the H2 sorption mechanism in MOFs was reported by the group of William A.Goddard III.[27] Previous works on the topic did not address the problem of the mechanism of hydrogen adsorption atroom temperature. In this work statistical ensembles were averaged to obtain the sorption mechanism with the grandcanonical ensemble. The multiple configurations that the H2 framework needs to explore at room temperature in thesorption process is a more physical meaningful method than single snapshots. After averaging the ensemble of allconfigurations, they found that for COFs and MOFs, the pore filling mechanism is predominant, while there are notclear evidence about the formation of single layers. [27]

Determining hydrogen storage capacityFor the characterization of MOFs as hydrogen storage materials, there are two hydrogen-uptake measurementmethods: gravimetric and volumetric. To obtain the total amount of hydrogen in the MOF, both the amount ofhydrogen absorbed on its surface and the amount of hydrogen residing in its pores should be considered. To calculatethe absolute absorbed amount (Nabs), the surface excess amount (Nex) is added to the product of the bulk density ofhydrogen (ρbulk) and the pore volume of the MOF (Vpore), as shown in the following equation:[48]

Nabs=Nex+(ρbulk)(Vpore)

Gravimetric method

The increased mass of the MOF due to the stored hydrogen is directly calculated by a highly sensitivemicrobalance.[48] The mass of the adsorbed hydrogen decreases when high pressure is applied to the system due toits buoyancy. This weight loss is calculated by the volume of the MOF’s frame and the density of hydrogen.[49]

Volumetric method

The changing of amount of hydrogen stored in the MOF is measured by detecting the varied pressure of hydrogen atconstant volume.[48] The volume of adsorbed hydrogen in the MOF is then calculated by subtracting the volume ofhydrogen in free space from the total volume of dosed hydrogen.[50]

Metal-organic framework 9

Other methods of hydrogen storageThere are six possible methods that can be used for the reversible storage of hydrogen with a high volumetric andgravimetric density, which are summarized in the following table, (where ρm is the gravimetric density, ρv is thevolumetric density, T is the working temperature, and P is the working pressure):[51]

Storage method ρm

 (mass%) ρv (kg

H2/m3)

T (°C) P (bar) Remarks

High-pressure gas cylinders 13 < 40 25 800 Compressed H2 gas in lightweight composite cylinder

Liquid hydrogen in cryogenictanks

size-dependent 70.8 - 252 1 Liquid H2; continuous loss of a few percent of H2 per day at 25 °C

Adsorbed hydrogen ≈ 2 20 - 80 100 Physisorption of H2 on materials

Adsorbed on interstitial sites ina host metal

≈ 2 150 25 1 Atomic hydrogen reversibly adsorbs in host metals

Complex compounds < 18 150 > 100 1 Complex compounds ([AlH4]- or [BH4]-); desorption at elevatedtemperature, adsorption at high pressures

Metal and complexes togetherwith water

< 40 > 150 25 1 Chemical oxidation of metals with water and liberation of H2

Of these, high-pressure gas cylinders and liquid hydrogen in cryogenic tanks are the least practical ways to storehydrogen for the purpose of fuel due to the extremely high pressure required for storing hydrogen gas or theextremely low temperature required for storing hydrogen liquid. The other methods are all being studied anddeveloped extensively.[51]

MOFs for catalysisMOFs have large potential in numerous catalyst applications. Catalysts are used to manufacture the majority of themost used chemicals in the world. The high surface area, tunable porosity, diversity in metal and functional groupsof MOFs makes them especially suited for use as catalysts. The study of MOFs for catalysts has only recently begunwith the majority of the work achieved during the last few years. The set geometry of the MOFs internal frameworkallows for their use as size selective catalysts. Previous work in this area was achievable only using zeolites. Butzeolites are limited by the fixed tetrahedral coordination of the Si/Al connecting points and the oxide linker and thereare only less than 200 zeolites present indicating its limitation in structure tuning whereas MOFs use versatilecoordination chemistry, polytopic linkers, and terminating ligands (F-, OH-, H2O among others) which makes itpossible to design an almost infinite variety of MOF structures. It is also difficult to obtain zeolites with pore sizeslarger than 1 nm, which limits the catalytic applications of zeolites to relatively small organic molecules (typicallyno larger than xylenes). Furthermore, mild synthetic conditions typically employed for MOF synthesis allow directincorporation of a variety of delicate functionalities into the framework structures. Such a process would not bepossible with zeolites or other microporous crystalline oxide-based materials because of the harsh conditionstypically used for their synthesis (e.g., calcination at high temperatures to remove organic templates). Again, zeolitesstill cannot be obtained in enantiopure form, which prevents applications of zeolites in catalytic asymmetricsynthesis of value-added chiral molecules for the pharmaceutical, agrochemical, and fragrance industries. Forexample, either enantiopure chiral ligands or their metal complexes can be incorporated directly into the frameworksof MOFs to lead to efficient asymmetric catalysts. Even some MOF materials may bridge the gap between zeolitesand enzymes when they combine isolated polynuclear sites, dynamic host-guest responses, and a hydrophobic cavityenvironment. MOFs might be useful for making semi-conductors. Theoretical calculations show that MOFs aresemiconductors or insulators with band gaps between 1.0 and 5.5 eV which can be altered by changing the degree ofconjugation in the ligands indicating its possibility for being photocatalysts.

Metal-organic framework 10

Design of MOFs for catalysis

Example of MOF-5

Like other heterogeneous catalysts, MOFs allow for easierpost-reaction separation and recyclability than homogeneous catalysts.In some cases, they also give a highly enhanced catalyst stability.Additionally, they typically offer substrate-size selectivity.Nevertheless, while clearly important for reactions in living systems,selectivity on the basis of substrate size is of limited value in abioticcatalysis, as reasonably pure feedstocks are generally available.

Catalysis with metal ions or metal clusters

Example of zeolite catalyst

Among the earliest reports of MOF-based catalysis was a descriptionin 1994 by Fujita and co-workers on the cyanosilylation of aldehydesby a 2D MOF (layered square grids) of formulaCd(4,4’-bpy)2(NO3)2.[52] This investigation centered mainly on size-and shape-selective clathration. A second set of examples are thosereported by Llabrés i Xamena et al. based on a two-dimensional,square-grid MOF containing single Pd(II) ions as nodes and2-hydroxypyrimidinolates as struts.[53] Despite initial coordinativesaturation, the palladium centers in this MOF proved capable ofcatalyzing alcohol oxidation, olefin hydrogenation, and Suzuki C–Ccoupling. At a minimum, these reactions necessarily entail redoxoscillations of the metal nodes between Pd(II) and Pd(0) intermediatesaccompanying by drastic changes in coordination number, whichwould certainly lead to destabilization and potential destruction of theoriginal framework if all the Pd centers are catalytically active. Theobservation of substrate shape- and size-selectivity implies that the catalytic reactions are heterogeneous and areindeed occurring within the MOF. Nevertheless, at least for hydrogenation, it is difficult to rule out the possibilitythat catalysis is occurring at the surface of MOF-encapsulated palladium clusters/nanoparticles (i.e., partialdecomposition sites) or defect sites, rather than at transiently labile, but otherwise intact, single-atom MOF nodes.Ravon et al. have extended studies of “opportunistic” MOF-based catalysis to the cubic compound, MOF-5.[54] Thismaterial comprises coordinatively saturated Zn4O nodes and a fully complexed bdc struts; yet it apparently catalyzesthe Friedel–Crafts tert-butylation of both toluene and biphenyl. Furthermore, para alkylation is strongly favored overortho alkylation, a behavior thought to reflect the encapsulation of reactants by the MOF.

Metal-organic framework 11

Catalysis with functional struts

The porous-framework material [Cu3(btc)2(H2O)3], also known as HKUST-1,[55] contains large cavities havingwindows of diameter ~6 Å. The coordinated water molecules are easily removed, leaving open Cu(II) sites. Kaskeland co-workers showed that these Lewis acid sites could catalyze the cyanosilylation of benzaldehyde or acetone.Alaerts et al. investigated the behavior of the anhydrous version of HKUST-1 as an acid catalyst.[56] Recognizing thepotential for opportunistic catalysis at defect sites (such as exposed carboxylic acids), they examined three reactions:isomerization of a-pinene oxide, cyclization of citronellal, and rearrangement of a-bromoacetals, whose productselectivity patterns differ significantly for Brøsted vs. Lewis acid-catalyzed pathways. Based on experimental data,these researchers concluded that [Cu3(btc)2] indeed functions primarily as a Lewis acid catalyst. Kaskel andco-workers also evaluated the behavior of MIL-101, a large-cavity MOF having the formula[Cr3F(H2O)2O(bdc)3] asa cyanosilylation catalyst.[57] The coordinated water molecules in MIL-101 are easily removed to expose Cr(III)sites. As one might expect, given the greater Lewis acidity of Cr(III) vs. Cu(II), MIL-101 is much more active thanHKUST-1 as a catalyst for the cyanosilylation of aldehydes. Additionally, the Kaskel group observed that thecatalytic sites of MIL-101, in contrast to those of HKUST-1, are immune to unwanted reduction by benzaldehyde.The Lewis-acid-catalyzed cyanosilylation of aromatic aldehydes has also been carried out by Long and co-workersusing a MOF of the formula Mn3[(Mn4Cl)3BTT8(CH3OH)10].[58] This material contains a three-dimensional porestructure, with the pore diameter equaling 10 Å. In principle, either of the two types of Mn(II) sites could function asa catalyst. Noteworthy features of this catalyst are high conversion yields (for small substrates) and goodsubstrate-size-selectivity, consistent with channellocalized catalysis.

Catalysis with MOF-encapsulated catalysts

The MOF encapsulation approach invites comparison to earlier studies of oxidative catalysis by zeolite-encapsulatedFe(porphyrin)[59] as well as Mn(porphyrin)[60] systems. The zeolite studies generally employed iodosylbenzene(PhIO), rather than TPHP as oxidant. The difference is likely mechanistically significant, thus complicatingcomparisons. Briefly, PhIO is a single oxygen atom donor, while TBHP is capable of more complex behavior. Inaddition, for the MOF-based system, it is conceivable that oxidation proceeds via both oxygen transfer from amanganese oxo intermediate as well as a manganese-initiated radical chain reaction pathway. Regardless ofmechanism, the approach is a promising one for isolating and thereby stabilizing the porphyrins against bothoxo-bridged dimer formation and oxidative degradation.[61]

Catalysis with metal-free organic cavity modifiers

Most examples of MOF-based catalysis make use of metal ions or atoms as active sites. Among the few exceptions are two nickel- and two copper-containing MOFs synthesized by Rosseinsky and co-workers.[62] These compounds employ amino acids(L- or D-aspartate) together with dipyridyls as struts. The coordination chemistry is such that the amine group of the aspartate cannot be protonated by added HCl, but one of the aspartate carboxylates can. Thus, the framework-incorporated amino acid can exist in a form that is not accessible for the free amino acid. While the nickel-based compounds are marginally porous, on account of tiny channel dimensions, the copper versions are clearly porous. The Rosseinsky group showed that the carboxylic acids behave as Brøsted acidic catalysts, facilitating (in the copper cases) the ring-opening methanolysis of a small, cavityaccessible epoxide at up to 65% yield. These researchers point out that superior homogeneous catalysts exist, but emphasize that the catalyst formed here is unique to the MOF environment, thus representing an interesting proof of concept. Kitagawa and co-workers have reported the synthesis of a catalytic MOF having the formula [Cd(4-btapa)2(NO3)2].[63] The MOF is three-dimensional, consisting of an identical catenated pair of networks, yet still featuring pores of molecular dimensions. The nodes consist of single cadmium ions, octahedrally ligated by pyridyl nitrogens. From a catalysis standpoint, however, the most interesting feature of this material is the presence of guest-accessible amide functionalities. The researchers showed that the amides are capable of base-catalyzing the Knoevenagel condensation of benzaldehyde with malononitrile. Reactions with larger nitriles, however, are only marginally accelerated,

Metal-organic framework 12

implying that catalysis takes place chiefly within the material’s channels rather than on its exterior. A noteworthyfinding is the lack of catalysis by the free strut in homogeneous solution, evidently due to intermolecular H-bondingbetween bptda molecules. Thus, the MOF architecture elicits catalytic activity not otherwise encountered. In aninteresting alternative approach, Férey and coworkers were able to modify the interior of MIL-101 via Cr(III)coordination of one of the two available nitrogen atoms of each of several ethylenediamine molecules.[64] The freenon-coordinated ends of the ethylenediamines were then used as Brøsted basic catalysts, again for Knoevenagelcondensation of benzaldehyde with nitriles. A third approach has been described by Kim and coworkers.[65] Using apyridine-functionalized derivative of tartaric acid and a Zn(II) source they were able to synthesize a 2D MOF termedPOST-1. POST-1 possesses 1D channels whose cross sections are defined by six trinuclear zinc clusters and sixstruts. While three of the six pyridines are coordinated by zinc ions, the remaining three are protonated and directedtoward the channel interior. When neutralized, the noncoordinated pyridyl groups are found to catalyzetransesterification reactions, presumably by facilitating deprotonation of the reactant alcohol. The absence ofsignificant catalysis when large alcohols are employed strongly suggests that the catalysis occurs within the channelsof the MOF.

MOFs for achiral catalysis

Schematic Diagram for MOF Catalysis

Metals in MOFs as catalytic sites

The metals in the MOF structure often act as Lewis acids. The metalsin MOFs often coordinate to labile solvent molecules or counter ionswhich can be removed after activation of the framework. The Lewisacidic nature of such unsaturated metal centers can activate thecoordinated organic substrates for subsequent organic transformations.The use of unsaturated metal centers was demonstrated in thecyanosilylation of aldehydes and imines by Fujita and coworkers in2004.[66] They reported MOF of composition {[Cd(4,4'-bpy)2(H2O)2] •(NO3)2 • 4H2O} which was obtained by treating linear bridging ligand4,4'-bipyridine (bpy) with Cd(NO3)2 . The Cd(II) centers in this MOF possesses a distorted octahedral geometryhaving four pyridines in the equatorial positions, and two water molecules in the axial positions to form atwo-dimensional infinite network. On activation, two water molecules were removed leaving the metal centersunsaturated and Lewis acidic. The Lewis acidic character of metal center was tested on cyanosilylation reactions ofimine where the imine gets attached to the Lewis-acidic metal centre resulting in higher electrophilicity of imines.For the cyanosilylation of imines, most of the reactions were complete within 1 h affording aminonitriles inquantitative yield. Kaskel and coworkers[67] carried out similar cyanosilylation reactions with coordinativelyunsaturated metals in three-dimensional (3D) MOFs as heterogeneous catalysts. The 3D framework[Cu3(btc)2(H2O)3] (btc: Benzene-1,3,5- tricarboxylate) (HKUST-1) used in this study was first reported by Williamset al.[68] The open framework of [Cu3(btc)2(H2O)3] is built from dimeric cupric tetracarboxylate units(paddle-wheels) with aqua molecules coordinating to the axial positions and btc bridging ligands. The resultingframework after removal of two water molecules from axial positions possesses porous channel. This activated MOFcatalyzes the trimethylcyanosilylation of benzaldehydes with a very low conversion (<5% in 24 h) at 293 K. As thereaction temperature was raised to 313 K, a good conversion of 57% with a selectivity of 89% was obtained after 72h. In comparison, less than 10% conversion was observed for the background reaction (without MOF) under thesame conditions. But this strategy suffers from some problems like 1) the decomposition of the framework withincrease of the reaction temperature due to the reduction of Cu(II) to Cu(I) by aldehydes; 2) strong solvent inhibitioneffect; electron donating solvents such as THF competed with aldehydes for coordination to the Cu(II) sites, and no

Metal-organic framework 13

cyanosilylation product was observed in these solvents; 3) the framework instability in some organic solvents.Several other groups have also reported the use of metal centres in MOFs as catalysts[69][70] Again,electron-deficient nature of some metals and metal clusters makes the resulting MOFs efficient oxidation catalysts.Mori and coworkers[71] reported MOFs with Cu2 paddle wheel units as heterogeneous catalysts for the oxidation ofalcohols. The catalytic activity of the resulting MOF was examined by carrying out alcohol oxidation with H2O2 asthe oxidant. It also catalyzed the oxidation of primary alcohol, secondary alcohol and benzyl alcohols with highselectivity. Hill et al.[72] have demonstrated the sulfoxidation of thioethers using an MOF based on vanadium-oxocluster V6O13 building units.

Functional Linkers in MOFs as catalytic sites

Functional linkers can be also utilized as catalytic sites. A 3D MOF {[Cd(4- btapa)2(NO3)2] • 6H2O • 2DMF}(4-btapa=1,3,5-benzene tricarboxylic acid tris [N-(4-pyridyl)amide], DMF= N,N-dimethylformamide) constructedby tridentate amide linkers and cadmium salt has been shown to catalyze the Knoevenagel condensation reaction byKitagawa and coworkers.[73] The pyridine groups on the ligand 4-btapa act as ligands binding to the octahedralcadmium centers, while the amide groups can provide the functionality for interaction with the incoming substrates.Specifically, the – NH moiety of the amide group can act as electron acceptor whereas the C=O group can act aselectron donor to activate organic substrates for subsequent reactions. Ferey et al.[74] reported a robust and highlyporous MOF [Cr3(μ3-O)F(H2O)2(bdc)3] (bdc: Benzene-1,4- dicarboxylate) where instead of directly using theunsaturated Cr(III) centers as catalytic sites, the authors grafted ethylenediamine (ED) onto the Cr(III) sites. Theuncoordinated ends of ED can act as base catalytic sites, ED-grafted MOF was investigated for Knoevenagelcondensation reactions. A significant increase in conversion was observed for ED-grafted MOF compared tountreated framework (98% vs 36%).

Entrapment of catalytically active noble metal nanoparticles in MOFs

The entrapment of catalytically active noble metals can be accomplished by grafting on functional groups to theunsaturated metal site on MOFs. Ethylenediamine (ED) has been shown to be grafted on the Cr metal sites byHwang and coworkers and can be further modified to encapsulate noble metals such as Pd.[75] The entraped Pd wasthen shown to have similar catalytic activity as Pd/C in the Heck reaction. Fisher and coworkers[76] showed thatruthenium nanoparticles have catalytic activity to a number of reactions when entrapped in the MOF-5 framework.With this Ru-encapsulated MOF oxidation of benzyl alcohol was reported at 25% efficiency to benzyl aldehyde, buta breakdown of the MOF structure was also noted whereas the hydrogenation of benzene to cyclohexane wasachieved at 25% efficiency with the MOF structure retained under a hydrogen atmosphere.

MOFs as reaction hosts with size selectivity

MOFs are useful for both photochemical and polymerization reactions due to the ability to tune pore size and shape.A 3D MOF {[Co(bpdc)3(bpy)] • 4DMF • H2O} (bpdc: biphenyldicarboxylate, bpy: 4,4'-bipyridine) was sythesizedby Li and coworkers.[77] Using this MOF photochemistry of o-methyl dibenzyl ketone (o-MeDBK) was extensivelystudied. This molecule was found to have a variety of photochemical reaction properties including the production ofcyclopentanol. MOFs have been used to study polymerization in the confined space of MOF channels.Polymerization reactions in confined space might have different properties than polymerization in open space.Styrene, divinylbenzene, substituted acetylenes, methyl methacrylate, and vinyl acetate have all been studied byKitagawa and coworkers as possible activated monomers for radical polymerization.[78][79] Due to the differentlinker size the MOF channel size could be tunable on the order of roughly 25 and 100 Å2. The channels were shownto stabalize propagating radicals and suppress termination reactions when used as radical polymerization sites.

Metal-organic framework 14

MOFs for asymmetric catalysisThere are several strategies to construct homochiral MOFs. Crystallization of homochiral MOFs via self-resolutionfrom achiral linker ligands is one of the way to accomplish such a goal. However, the resulting bulk samples containboth enantiomorphs and are racemic. Aoyama and coworkers[80] successfully obtained homochiral MOFs in the bulkfrom achiral ligands by carefully controlling nucleation in the crystal growth process. Zheng and coworkers[81]

reported the synthesis of homochiral MOFs from achiral ligands by chemically manipulating the statisticalfluctuation of the formation of enantiomeric pairs of crystals. Growing MOF crystals under chiral influences isanother approach to obtain homochiral MOFs using achiral linker ligands. Rosseinsky and coworkers[82][83] haveintroduced a chiral coligand to direct the formation of homochiral MOFs by controlling the handedness of the helicesduring the crystal growth. Morris and coworkers[84] utilized ionic liquid with chiral cations as reaction media forsynthesizing MOFs, and obtained homochiral MOFs. The most straightforward and rational strategy for synthesizinghomochiral MOFs is, however, to use the readily available chiral linker ligands for their construction.

Homochiral MOFs with interesting functionalities and reagent-accessible channels

Homochiral MOFs have been made by Lin and coworkers using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl(BINAP), 1,1'-bi-2,2'-naphthol (BINOL) as a chiral ligands.[85] These ligands can coordinate with catalytically activemetal sites to enhance the enantioselectivity. A variety of linking groups such as pyridine, phosphonic acid, andcarboxylic acid can be selectively introduced to the 3,3', 4,4', and the 6,6' positions of the 1,1'-binaphthyl moiety.Moreover, by changing the length of the linker ligands the porosity and framework structure of the MOF can beselectivily tuned.

Postmodification of homochiral MOFs

Lin and coworkers have shown that the postmodification of MOFs can be achieved to produce enantioslelctivehomochiral MOFs for use as catalysts.[86] The resulting 3D homochiral MOF {[Cd3(L)3Cl6]• 4DMF • 6MeOH •3H2O} (L= (R)-6,6'-dichloro-2,2'-dihydroxyl-1,1'-binaphthyl-bipyridine) synthesized by Lin was shown to have asimilar catalytic efficiency for the diethylzinc addition reaction as compared to the homogeneous analogue when waspretreated by Ti(OiPr)4 to generate the grafted Ti- BINOLate species. The catalytic activity of MOFs can varydepending on the framework structure. Lin and others found that MOFs synthesized from the same materials couldhave drastically different catalytic activities depending on the framework structure present.[87]

Homochiral MOFs with precatalysts as building blocks

Another approach to construct catalytically active homochiral MOFs is to incorporate chiral metal complexes whichare either active catalysts or precatalysts directly into the framework structures. For example, Hupp andcoworkers[88] have combined a chiral ligand and bpdc (bpdc: biphenyldicarboxylate) with Zn(NO3)2 and obtainedtwofold interpenetrating 3D networks. The orientation of chiral ligand in the frameworks makes all Mn(III) sitesaccessible through the channels. The resulting open frameworks showed catalytic activity towards asymmetric olefinepoxidation reactions. No significant decrease of catalyst activity was observed during the reaction and the catalystcould be recycled and reused several times. Lin and coworkers[89] have reported zirconium phosphonate-derivedRu-BINAP systems. Zirconium phosphonate-based chiral porous hybrid materials containing theRu(BINAP)(diamine)Cl2 precatalysts showed excellent enantioselectivity (up to 99.2% ee) in the asymmetrichydrogenation of aromatic ketones.

Metal-organic framework 15

MOFs towards biomimetic design and photocatalysisSome MOF materials may resemble enzymes when they combine isolated polynuclear sites, dynamic host-guestresponses, and hydrophobic cavity environment which are characteristics of an enzyme.[90] Some well-knownexamples of cooperative catalysis involving two metal ions in biological systems include: the diiron sites in methanemonooxygenase, dicopper in cytochrome c oxidase, and tricopper oxidases which have analogy with polynuclearclusters found in the 0D coordination polymers, such as binuclear Cu2 paddlewheel units found in MOP-1[91][92] and[Cu3(btc)2] (btc = benzene-1,3,5-tricarboxylate) in HKUST-1 or trinuclear units such as {Fe3O(CO2)6} inMIL-88,[93] and IRMOP-51.[94] Thus, 0D MOFs have accessible biomimetic catalytic centers. In enzymatic systems,protein units show “molecular recognition", high affinity for specific substrates. It seems that molecular recognitioneffects are limited in zeolites by the rigid zeolite structure.[95] In contrast, dynamic features and guest-shape responsemake MOFs more similar to enzymes. Indeed many hybrid frameworks contain organic parts that can rotate as aresult of stimuli, such as light and heat.[96] The porous channels in MOF structures can be used as photocatalysissites. In photocatalysis, the use of mononuclear complexes is usually limited either because they only undergosingle- electron process or from the need for high-energy irradiation. In this case, binuclear systems have a numberof attractive features for the development of photocatalysts.[97] For 0D MOF structures, polycationic nodes can act assemiconductor quantum dots which can be activated upon photostimuli with the linkers serving as photonantennae.[98] Theoretical calculations show that MOFs are semiconductors or insulators with band gaps between 1.0and 5.5 eV which can be altered by changing the degree of conjugation in the ligands.[99] Experimental results showthat the band gap of IRMOF-type samples can be tuned by varying the functionality of the linker.[100]

Other applications of MOFsThere are many potential uses of MOFs other than hydrogen storage, such as gas purification, gas separation, gasstorage (other than hydrogen), and heterogeneous catalysis. MOFs are promising for gas purification because ofstrong chemisorption that takes place between electron-rich, odor-generating molecules (such as amines, phosphines,oxygenates, alcohols, water, or sulfur-containing molecules) and the framework, allowing the desired gas to passthrough the MOF. Gas separation can be performed with MOFs because they can allow certain molecules to passthrough their pores based on size and kinetic diameter. This is particularly important for separating out carbondioxide. Regarding gas storage, MOFs can store molecules such as carbon dioxide, carbon monoxide, methane, andoxygen due to their high adsorption enthalpies (similar to hydrogen). Finally, MOFs are used for catalysis because oftheir shape and size selectivity and their accessible bulk volume. Also, because of their very porous architecture,mass transport in the pores is not hindered.[2]

Methane storageOmar M. Yaghi and William A. Goddard III also reported the uptake for MOF-177 and they compared it to theuptake of Covalent Organic Frameworks. They found that the total uptake and delivery amount in COF-102 andCOF-103 outperform other 2D and 3D-COFs at high pressure, even the benchmark MOF-177.[101] More recently onOctober of 2011, new COFs with better delivery amount have been designed in the lab of William A. Goddard III,and they have been shown to be stable and overcome the DOE target in delivery basis. COF-103-Eth-trans andCOF-102-Ant, are found to exceed the DOE target of 180 v(STP)/v at 35 bar for methane storage. Thus at 35 bar (inv(STP)/v delivery units) the best performers is COF-103-Eth-trans which stores 5.6 times as much as bulk CH4 at thesame pressure (bulk CH4 reaches 34). All the designed COFs have superior performance to previously reportedCOFs and MOFs, such as COF-102 (137), MOF-177 (112), and MOF-200 (81 v(STP)/v delivery units).[102] Thenew materials were designed for best performance at 35 bar. They reported that using thin vinyl bridging groups aidperformance by minimizing the interaction methane-COF at low pressure. This can be extended to MOFs. This is anew feature that can be used to enhance loading in addition to the common practice of adding extra fused benzenerings.[102]

Metal-organic framework 16

References[1][1] Jiří Čejka (ed.) "Metal-Organic Frameworks Applications from Catalysis to Gas Storage" Wiley-VCH, Weinheim, 2011. 392 pp. ISBN

978-3-527-32870-3[2] Czaja, Alexander U.; Trukhan, Natalia; Müller, Ulrich (2009). "Industrial applications of metal-organic frameworks". Chemical Society

Reviews 38 (5): 1284–1293. doi:10.1039/b804680h. PMID 19384438.[3] Tranchemontagne, David J.; Mendoza-Cortés, José L.; O'Keefe, Michael; Yaghi, Omar M. (2009). "Secondary building units, nets and

bonding in the chemistry of metal-organic frameworks". Chemical Society Reviews 38 (5): 1257–1283. doi:10.1039/b906666g.PMID 19384437.

[4] Tranchemontagne David J.; Mendoza-Cortes Jose L.; O'Keeffe Michael; Yaghi OM; Secondary building units, nets and bonding in thechemistry of metal-organic frameworks . Supplementary material (http:/ / www. its. caltech. edu/ ~jmendoza/ Other_Publications. html)

[5] Janiak, Christoph (2003). "Engineering coordination polymers towards applications". Dalton Transactions: 2781–2804.doi:10.1039/b305705bg.

[6] IUPAC Current Projects. (http:/ / www. iupac. org/ indexes/ Projects/ years/ 2009) May 09, 2010. Retrieved on May 09, 2010.[7] CP and MOF Project. (http:/ / www. iupac. org/ web/ ins/ 2009-012-2-200) May 09, 2010. Retrieved on May 09, 2010.[8] Batten, Stuart R.; Champness, Neil R.; Chen, Xiao-Ming; Garcia-Martinez, Javier; Kitagawa, Susumu; Öhrström, Lars; O'Keeffe, Michael;

Suh, Myunghyun P. et al. (2012). "Coordination polymers, metal–organic frameworks and the need for terminology guidelines" (http:/ / pubs.rsc. org/ en/ Content/ ArticleLanding/ 2012/ CE/ C2CE06488J). CrystEngComm (RSC). doi:10.1039/C2CE06488J. .

[9] Cheetham, Rao, and Feller. Structural diversity and chemical trends in hybrid inorganic-organic framework materials. Chem. Comm. 46(2006) 4780. doi:10.1039/b610264f

[10] http:/ / rcsr. anu. edu. au/[11] Cheetham, Anthony K.; Ferey, Gerard; Loiseau, Thierry (1999). "Open-framework inorganic materials". Angewandte Chemie, International

Edition 38 (22): 3268–3292. doi:10.1002/(SICI)1521-3773(19991115)38:22<3268::AID-ANIE3268>3.0.CO;2-U. PMID 10602176.[12] Bucar, Dejan-Kresimir; Papaefstathiou, Giannis S.; Hamilton, Tamara D.; Chu, Quanli L.; Georgiev, Ivan G.; MacGillivray, Leonard R.

(2007). "Template-controlled reactivity in the organic solid state by principles of coordination-driven self-assembly.". European Journal ofInorganic Chemistry 2007 (29): 4559–4568. doi:10.1002/ejic.200700442.

[13] Parnham, Emily R.; Morris, Russell E. (2007). "Ionothermal Synthesis of Zeolites, Metal-Organic Frameworks, and Inorganic-OrganicHybrids.". Accounts of Chemical Research 40 (10): 1005–1013. doi:10.1021/ar700025k. PMID 17580979.

[14] Dincǎ, Mircea; Long, Jeffrey R. (2008). "Hydrogen storage in microporous metal-organic frameworks with exposed metal sites".Angewandte Chemie International Edition 47 (36): 6766–6779. doi:10.1002/anie.200801163. PMID 18688902.

[15] Wang, Zhenqiang; Cohen, Seth M. (2009). "Postsynthetic modification of metal–organic frameworks". Chemical Society Reviews 38 (5):1315–1329. doi:10.1039/b802258p. PMID 19384440.

[16] Das, Sunirban; Kim, Hyunuk; Kim, Kimoon (2009). "Metathesis in Single Crystal: Complete and Reversible Exchange of Metal IonsConstituting the Frameworks of Metal-Organic Frameworks.". Journal of the American Chemical Society 131 (11): 3814–3815.doi:10.1021/ja808995d. PMID 19256486.

[17] Ni, Zheng; Masel, Richard I. (2006). "Rapid production of metal−organic frameworks via microwave-assisted solvothermal synthesis".Journal of the American Chemical Society 128 (38): 12394–12395. doi:10.1021/ja0635231. PMID 16984171.

[18] Choi, Jung-Sik; Son, Won-Jin; Kim, Jahoen; Ahn, Wha-Seung (2008). "Metal–organic framework MOF-5 prepared by microwave heating:Factors to be considered". Microporous and Mesoporous Materials 116 (1–3): 727–731. doi:10.1016/j.micromeso.2008.04.033.

[19] Pichon, Anne; James, Stuart L. (2008). "An array-based study of reactivity under solvent-free mechanochemical conditions—insights andtrends". CrystEngComm 10 (12): 1839–1847. doi:10.1039/B810857A.

[20] "MOF Technologies Ltd" (http:/ / www. moftechnologies. com). . Retrieved 14 August 2012.[21][21] D. Braga CrystEngComm 2007, 9, p879[22] Murray, Leslie J.; Dincǎ, Mircea; Long, Jeffrey R. (2009). "Hydrogen storage in metal-organic frameworks". Chemical Society Reviews 38

(5): 1294–1314. doi:10.1039/b802256a. PMID 19384439.[23] Li, Yingwei; Yang, Ralph T. (2007). "Hydrogen Storage on Platinum Nanoparticles Doped on Superactivated Carbon". Journal of Physical

Chemistry C 111 (29): 11086–11094. doi:10.1021/jp072867q.[24] Committee on Alternatives and Strategies for Future Hydrogen Production and Use, National Research Council, National Academy of

Engineering. (2004). The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs. Washington, D.C.: National Academies.pp. 11–24, 37–44. ISBN 0-309-09163-2.

[25][25] United States Department of Energy (2004). "Basic Research Needs for the Hydrogen Economy."[26] Eberle, Ulrich; Felderhoff, Michael; Schüth, Ferdi (2009). "Chemical and physical solutions for hydrogen storage". Angewandte Chemie

International Edition 48 (36): 6608–6630. doi:10.1002/anie.200806293. PMID 19598190.[27] Mendoza-Cortes, JL; Han, SS; Goddard, WA; High H2 Uptake in Li-, Na-, K-Metalated Covalent Organic Frameworks and Metal Organic

Frameworks at 298 K. J. Phys. Chem. A. 2012, 116, pp 1621–1631. DOI: 10.1021/jp206981d[28] Krieck, S.; Gorls, H.; Westerhausen, M., Alkali Metal-Stabilized 1,3,5-Triphenylbenzene Monoanions: Synthesis and Characterization of the

Lithium, Sodium, and Potassium Complexes. Organometallics. 2010, 29, pp 6790–6800. DOI: 10.1021/om1009632[29] Han SS; Mendoza-Cortes JL; Goddard WA.; Recent advances on simulation and theory of hydrogen storage in metal–organic frameworks

and covalent organic frameworks. Chemical Society Reviews. 2009, 38, pp 1460-1476. DOI: 10.1039/B802430H

Metal-organic framework 17

[30] Yang, J.; A. Sudik, C. Wolverton, D. J. Siegel (2010). "High capacity hydrogen storage materials: attributes for automotive applications andtechniques for materials discovery" (http:/ / pubs. rsc. org/ en/ Content/ ArticleLanding/ 2010/ CS/ b802882f). Chem. Soc. Rev. 39 (2):656–675. doi:10.1039/b802882f. PMID 20111786. .

[31] Yan, Yong; Lin, Xiang; Yang, Sihai; Blake, Alexander J.; Dailly, Anne; Champness, Neil R.; Hubberstey, Peter; Schröder, Martin (2009)."Exceptionally high H2 storage by a metal-organic polyhedral framework". Chemical Communications (9): 1025–1027.doi:10.1039/b900013e.

[32] Sumida, Kenji; Hill, Matthew R.; Horike, Satoshi; Dailly, Anne; Long, Jeffrey R. (2009). "Synthesis and hydrogen storage properties ofBe12(OH)12(1,3,5-benzenetribenzoate)4". Journal of the American Chemical Society 131 (42): 15120–15121. doi:10.1021/ja9072707.PMID 19799422.

[33] Furukawa, H; Ko, N; Go, YB; Aratani, N; Choi, SB; Choi, E; ; Snurr, RQ; O'Keeffe, M; Kim, J; Yaghi, OM; Ultrahigh Porosity inMetal-Organic Frameworks. Science. 2010, 329, pp 424-428. DOI: 10.1126/science.1192160

[34] Rowsell, Jesse L. C.; Millward, Andrew R.; Park, Kyo Sung; Yaghi, Omar M. (2004). "Hydrogen sorption in functionalized metal−organicframeworks". Journal of the American Chemical Society 126 (18): 5666–5667. doi:10.1021/ja049408c. PMID 15125649.

[35] Rosi, Nathaniel L.; Eckert, Juergen; Eddaoudi, Mohamed; Vodak, David T.; Kim, Jaheon; O'Keefe, Michael; Yaghi, Omar M. (2003)."Hydrogen storage in microporous metal-organic frameworks". Science 300 (5622): 1127–1129. doi:10.1126/science.1083440.PMID 12750515.

[36] Dincǎ, Mircea; Dailly, Anne; Liu, Yun; Brown, Craig M.; Neumann, Dan A.; Long, Jeffrey R. (2006). "Hydrogen storage in a microporousmetal−organic framework with exposed Mn2+ coordination sites". Journal of the American Chemical Society 128 (51): 16876–16883.doi:10.1021/ja0656853. PMID 17177438.

[37] Lee, JeongYong; Li, Jing; Jagiello, Jacek (2005). "Gas sorption properties of microporous metal organic frameworks". Journal of Solid StateChemistry 178 (8): 2527–2532. doi:10.1016/j.jssc.2005.07.002.

[38] Rowsell, Jesse L. C.; Yaghi, Omar M. (2005). "Strategies for hydrogen storage in metal-organic frameworks". Angewandte ChemieInternational Edition 44 (30): 4670–4679. doi:10.1002/anie.200462786. PMID 16028207.

[39] Rowsell, Jesse L. C.; Yaghi, Omar M. (2006). "Effects of functionalization, catenation, and variation of the metal oxide and organic linkingunits on the low-pressure hydrogen adsorption properties of metal−organic frameworks". Journal of the American Chemical Society 128 (4):1304–1315. doi:10.1021/ja056639q. PMID 16433549.

[40] Garrone, E; Bonelli, B; Arean, C. O. (2008). "Enthalpy-entropy correlation for hydrogen adsorption on zeolites". Chemical Physics Letters456 (1–3): 68–70. doi:10.1016/j.cplett.2008.03.014.

[41] Kubas, G. J. (2001). Metal Dihydrogen and σ-Bond Complexes: Structure, Theory, and Reactivity. New York: Kluwer Academic.[42] Bellarosa, Luca (2012). "Early stages in the degradation of Metal-Organic Frameworks in liquid water from first-principles Molecular

Dynamics". Phys Chem Chem Phys in press. doi:10.1039/C2CP40339K.[43] Dolgonos, Grygoriy (2005). "How many hydrogen molecules can be inserted into C60? Comments on the paper 'AM1 treatment of

endohedrally hydrogen doped fullerene, nH2@C60' by L. Türker and Ş. Erkoç'". Journal of Molecular Structure: THEOCHEM 723 (1–3):239–241. doi:10.1016/j.theochem.2005.02.017.

[44] Tsao, Cheng-Si; Yu, MingSheng; Wang, Cheng-Yu; Liao, Pin-Yen; Chen, Hsin-Lung; Jeng, U-Ser; Tzeng, Yi-Ren; Chung, Tsui-Yun et al.(2009). "Nanostructure and hydrogen spillover of bridged metal-organic frameworks". Journal of the American Chemical Society 131 (4):1404–1406. doi:10.1021/ja802741b. PMID 19140765.

[45] Mulfort, Karen L.; Farha, Omar K.; Stern, Charlotte L.; Sarjeant, Amy A.; Hupp, Joseph T. (2009). "Post-synthesis alkoxide formationwithin metal-organic framework materials: A strategy for incorporating highly coordinatively unsaturated metal ions". Journal of theAmerican Chemical Society 131 (11): 3866–3868. doi:10.1021/ja809954r. PMID 19292487.

[46] Huang, B. L.; Ni, Z.; Millward, A.; McGaughey, A. J. H.; Uher, C.; Kaviany, M.; Yaghi, O. (2007). "Thermal conductivity of ametal-organic framework (MOF-5): Part II. Measurement". International Journal of Heat and Mass Transfer 50 (3–4): 405–411.doi:10.1016/j.ijheatmasstransfer.2006.10.001.

[47] McQuarrie, D. A.; Simon, J. D. (1997). Physical Chemistry: A Molecular Approach. Sausalito, CA: University Science Books.[48] Zhao, Dan; Yan, Daqiang; Zhou, Hong-Cai (2008). "The current status of hydrogen storage in metal–organic frameworks". Energy &

Environmental Science 1 (1): 225–235. doi:10.1039/b808322n.[49] Furukawa, Hiroyasu; Miller, Michael A.; Yaghi, Omar M. (2007). "Independent verification of the saturation hydrogen uptake in MOF-177

and establishment of a benchmark for hydrogen adsorption in metal–organic frameworks". Journal of Materials Chemistry 17 (30):3197–3204. doi:10.1039/b703608f.

[50] Lowell, S.; Shields, Joan E.; Thomas, Martin A.; Thommes, Matthias (2004). Characterization of Porous Solids and Powders: Surface Area,Pore Size and Density. Kluwer Academic Publishers.

[51] Züttel, Andreas (2004). "Hydrogen storage methods". Naturwissenschaften 91 (4): 157–172. doi:10.1007/s00114-004-0516-x.PMID 15085273.

[52] M. Fujita, Y. J. Kwon, S. Washizu and K. Ogura, (1994). "Metal-Organic Frameworks: A Rapidly Growing Class of Versatile NanoporousMaterial". J. Am. Chem. Soc. 116: 1151. doi:10.1021/ja00082a055.

[53] F. X. Llabrés i Xamena, A. Abad, A. Corma and H. Garcia, (2007). "MOFs as catalysts: Activity, reusability and shape-selectivity of aPd-containing MOF". J. Catal. 250: 294. doi:10.1016/j.jcat.2007.06.004.

[54] U. Ravon, M. E. Domine, C. Gaudillere, A. Desmartin-Chomel and D. Farrusseng, (2008). "MOFs as acid catalysts with shape selectivityproperties". New J. Chem. 32: 937. doi:10.1039/B803953B.

Metal-organic framework 18

[55] S. S. Chui, S. M. Lo, J. P. Charmant, A. G. Orpen and I. D. Williams, (1999). "A Chemically Functionalizable Nanoporous Material[Cu3(TMA)2(H2O)3]n". Science 283: 1148. doi:10.1126/science.283.5405.1148.

[56] L. Alaerts, E. Séguin, H. Poelman, F. Thibault-Starzyk, P. A. Jacobs and D. E. D. Vos, (2006). "Probing the Lewis Acidity and CatalyticActivity of the Metal–Organic Framework [Cu3(btc)2] (BTC=Benzene-1,3,5-tricarboxylate)". Chem.-Eur. J. 12: 7353.doi:10.1002/chem.200600220.

[57] A. Henschel, K. Gedrich, R. Kraehnert and S. Kaskel, (2008). "Catalytic properties of MIL-101". Chem. Commun.: 4192.doi:10.1039/B718371B.

[58] S. Horike, M. Dinca, K. Tamaki and J. R. Long, (2008). "Size-Selective Lewis-Acid Catalysis in a Microporous Metal-Organic Frameworkwith Exposed Mn2+ Coordination Sites". J. Am. Chem. Soc. 130: 5854. doi:10.1021/ja800669j.

[59] F. C. Skrobot, I. L. V. Rosa, A. P. A. Marques, P. R. Martins, J. Rocha, A. A. Valente and Y. Iamamoto, (2010). "CMPs as Scaffolds forConstructing Porous Catalytic Frameworks: A Built-in Heterogeneous Catalyst with High Activity and Selectivity Based on NanoporousMetalloporphyrin Polymers". J. Am. Chem. Soc. 237: 86. doi:10.1021/ja1028556.

[60] A. K. Rahiman, K. Rajesh, K. S. Bharathi, S. Sreedaran and V. Narayanan, (2009). "Catalytic oxidation of alkenes by manganese(III)porphyrin-encapsulated Al, V, Si-mesoporous molecular sieves". Inorg. Chim. Acta. 352: 1491. doi:10.1016/j.ica.2008.07.011.

[61] D. Mansuy, J. F. Bartoli and M. Momenteau, (1982). "Alkane hydroxylation catalyzed by metalloporhyrins : evidence for different activeoxygen species with alkylhydroperoxides and iodosobenzene as oxidants". Tetrahedron Lett., 23: 2781. doi:10.1016/S0040-4039(00)87457-2.

[62] M. J. Ingleson, J. P. Barrio, J. Bacsa, C. Dickinson, H. Park and M. J. Rosseinsky, (2008). "Generation of a solid Brønsted acid site in achiral framework". Chem. Commun.: 1287. doi:10.1039/B718443C.

[63] S. Hasegawa, S. Horike, R. Matsuda, S. Furukawa, K. Mochizuki, Y. Kinoshita and S. Kitagawa, (2007). "Three-Dimensional PorousCoordination Polymer Functionalized with Amide Groups Based on Tridentate Ligand: Selective Sorption and Catalysis". J. Am. Chem. Soc.129 (9): 2607–14. doi:10.1021/ja067374y. PMID 17288419.

[64] Y. K. Hwang, D.-Y. Hong, J.-S. Chang, S. H. Jhung, Y.-K. Seo, J. Kim, A. Vimont, M. Daturi, C. Serre and G. Férey, (2008). "AmineGrafting on Coordinatively Unsaturated Metal Centers of MOFs: Consequences for Catalysis and Metal Encapsulation". Angew. Chem. Int.Ed. 47: 4144. doi:10.1002/anie.200705998.

[65] J. S. Seo, D. Whang, H. Lee, S. I. Jun, J. Oh, Y. J. Jeon and K. Kim, (2000). "A homochiral metal–organic porous material forenantioselective separation and catalysis". Nature 404: 982. doi:10.1038/35010088.

[66] Ohmori, O.; Fujita, M. (2004). "Heterogeneous catalysis of a coordination network: cyanosilylation of imines catalyzed by aCd(II)-(4,4′-bipyridine) square grid complex". Chem. Commun.: 1586. doi:10.1039/B406114B.

[67] K. Schlichte, T. Kratzke, S. Kaskel (2004). "Improved synthesis, thermal stability and catalytic properties of the metal-organic frameworkcompound Cu3(BTC)2". Microporous Mesoporous Mater. 73: 81–85. doi:10.1016/j.micromeso.2003.12.027.

[68] S. S. Y. Chui, S. M. F. Lo, J. P. H. Charmant, A. G. Orpen, I. D. Williams (1999). "A Chemically Functionalizable Nanoporous Material[Cu3(TMA)2(H2O)3]n". Science 283: 1148. doi:10.1126/science.283.5405.1148.

[69] S. Horike, M. Dinca, K. Tamaki, J. R. Long (2008). "Size-Selective Lewis Acid Catalysis in a Microporous Metal-Organic Framework withExposed Mn2+ Coordination Site". J. Am. Chem. Soc. 130: 5854. doi:10.1021/ja800669j.

[70] O. R. Evans, H. L. Ngo, W. B. Lin (2001). "Chiral Porous Solids Based on Lamellar Lanthanide Phosphonates". J. Am. Chem. Soc. 123:10395. doi:10.1021/ja0163772.

[71] C. N. Kato, M. Hasegawa, T. Sato, A. Yoshizawa, T. Inoue, W. Mori (2005). "Microporous dinuclear copper(II)trans-1,4-cyclohexanedicarboxylate: heterogeneous oxidation catalysis with hydrogen peroxide and X-ray powder structure of peroxocopper(II) intermediate". J. Catal. 230: 226. doi:10.1016/j.jcat.2004.11.032.

[72] J. W. Han, C. L. Hill (2007). "A Coordination Network That Catalyzes O2-Based Oxidations". J. Am. Chem. Soc. 129: 15094.doi:10.1021/ja069319v.

[73] Hasegawa, S.; Horike, S.; Matsuda, R.; Kitagawa, S. et. al. (2007). "Three-Dimensional Porous Coordination Polymer Functionalized withAmide Groups Based on Tridentate Ligand: Selective Sorption and Catalysis". J. Am. Chem. Soc. 129: 2607–2614. doi:10.1021/ja067374y.PMID 17288419.

[74] G. Ferey, C. Mellot-Draznieks, C. Serre, F. Millange, J. Dutour, S. Surble, I. Margiolaki (2005). "A Chromium Terephthalate-Based Solidwith Unusually Large Pore Volumes and Surface Area". Science 309: 2040. doi:10.1126/science.1116275.

[75] Hwang, Y.; Hong, Y.; Chang, J.; Jhung, S. et. al. (2008). "Amine Grafting on Coordinatively Unsaturated Metal Centers of MOFs:Conse3quences for Catalysis and Metal Encapsulation". Angew Chem Int Ed 47: 4144–4148. doi:10.1002/anie.200705998.

[76] F. Schroeder, D. Esken, M. Cokoja, M. W. E. van der Berg, O. I. Lebedev, G. van Tendeloo, B. Walaszek, G. Buntkowsky, H. H. Limbach,B. Chaudret, R. A. Fischer (2008). "Ruthenium Nanoparticles inside Porous [Zn4O(bdc)3] by hydrogenolysis of Adsorbed [Ru(cod)(cot)]: ASolid-State Reference System for Surfactant-Stabilized Ruthenium Colloids". J. Am. Chem. Soc. 130: 6119–6130. doi:10.1021/ja078231u.

[77] Pan, L.; Liu, H.; Lei, X.; Haung, X.; Olson, D.; Turro, N.; Li, J. (2003). "A Recyclable Nanoporous Material Suitable for Ship-In-BottleSynthesis and Large Hydrocarbon Sorption". Angew. Chem. Int. Ed. 42: 542–546. doi:10.1002/anie.200390156.

[78] Uemura, T.; Kitaura, R.; Ohta, Y.; Nagaoka, M.; Kitagawa, S. (2006). "Nanochannel-Promoted Polymerization of Substituted Acetylenes inPorous Coordination Polymers". Angew. Chem. Int. Ed. 45: 4112–4116. doi:10.1002/anie.200600333.

[79] Uemura, T.; Hiramatsu, D.; Kubota, Y.; Takata, M.; Kitagawa, S. (2007). "Topotactic Linear Radical Polymerization of Divinylbenzenes inPorous Coordination Polymers". Angew. Chem. Int. Ed. 46: 4987–4990. doi:10.1002/anie.200700242.

[80] T. Ezuhara, K. Endo, Y. Aoyama (1999). "Helical Coordination Polymers from Achiral Components in Crystals. Homochiral Crystallization, Homochiral Helix Winding in the Solid State, and Chirality Control by Seeding". J. Am. Chem. Soc. 121: 3279.

Metal-organic framework 19

doi:10.1021/ja9819918.[81] S. T. Wu, Y. R. Wu, Q. Q. Kang, H. Zhang, L. S. Long, Z. P. Zheng, R. B. Huang, L. S. Zheng (2007). "Chiral Symmetry Breaking by

Chemically Manipulating Statistical Fluctuation in Crystallization". Angew. Chem. Int. Ed. 46: 8475. doi:10.1002/anie.200703443.[82] C. J. Kepert, T. J. Prior, M. J. Rosseinsky (2000). "A Versatile Family of Interconvertible Microporous Chiral Molecular Frameworks: The

First Example of Ligand Control of Network Chirality". J. Am. Chem. Soc. 122: 5158. doi:10.1021/ja993814s.[83] D. Bradshaw, T. J. Prior, E. J. Cussen, J. B. Claridge, M. J. Rosseinsky (2004). "Permanent Microporosity and Enantioselective Sorption in

a Chiral Open Framework". J. Am. Chem. Soc. 126: 6106. doi:10.1021/ja0316420.[84] Z. Lin, A. M. Z. Slawin, R. E. Morris (2007). "Chiral Induction in the Ionothermal Synthesis of a 3-D Coordination Polymer". J. Am. Chem.

Soc. 129: 4880. doi:10.1021/ja070671y.[85] Hu, A.; Ngo, H.; Lin, W. (2004). "Remarkable 4,4′-Substituent Effects on Binap: Highly Enantioselective Ru Catalysts for Asymmetric

Hydrogenation of β-Aryl Ketoesters and Their Immobilization in Room-Temperature Ionic Liquids". Angew. Chem. Int. Ed.: 2501–2504.doi:10.1002/anie.200353415.

[86] Wu, C.; Hu., A.; Zhang, L.; Lin, W. (June 2005). "A Homochiral Porous Metal−Organic Framework for Highly EnantioselectiveHeterogeneous Asymmetric Catalysis". J. Am. Chem. Soc. 127 (25): 8940–8941. doi:10.1021/ja052431t. PMID 15969557.

[87] C. Wu, W. B. Lin (2007). "Heterogeneous Asymmetric Catalysis with Homochiral Metal–Organic Frameworks:Network-Structure-Dependent Catalytic Activity". Angew. Chem. Int. Ed. 46: 1075. doi:10.1002/anie.200602099.

[88] S. H. Cho, B. Q. Ma, S. T. Nguyen, J. T. Hupp, T. E. Albrecht-Schmitt (2007). "A Metal-Organic Framework Material That Functions as anEnantioselective Catalyst for Olefin Epoxidation". Chem. Commun.: 2563. doi:10.1039/b600408c.

[89] A. G. Hu, H. L. Ngo, W. B. Lin (2003). "Chiral Porous Hybrid Solids for Practical Heterogeneous Asymmetric Hydrogenation of AromaticKetones". J. Am. Chem. Soc. 125: 11490. doi:10.1021/ja0348344.

[90] D. Farrusseng, S. Aguado, C. Pinel (2009). "Metal–Organic Frameworks: Opportunities for Catalysis". Angew. Chem. Int. Ed. 48:7502–7513. doi:10.1002/anie.200806063.

[91] M. Eddaoudi, J. Kim, J. B. Wachter, H. K. Chae, M. O'Keeffe, O. M. Yaghi (2001). "Porous Metal−Organic Polyhedra: 25 ÅCuboctahedron Constructed from 12 Cu2(CO2)4 Paddle-Wheel Building Blocks". J. Am. Chem. Soc. 123: 4368. doi:10.1021/ja0104352.

[92] H. Furukawa, J. Kim, N. W. Ockwig, M. O'Keeffe, O. M. Yaghi, (2008). "Control of Vertex Geometry, Structure Dimensionality,Functionality, and Pore Metrics in the Reticular Synthesis of Crystalline Metal−Organic Frameworks and Polyhedra". J. Am. Chem. Soc. 130:11650. doi:10.1021/ja803783c.

[93] S. Surble, C. Serre, C. Mellot-Draznieks, F. Millange, G. Ferey (2006). "A new isoreticular class of metal-organic-frameworks with theMIL-88 topology". Chem. Commun.: 284. doi:10.1039/B512169H.

[94] A. C. Sudik, A. R. Millward, N. W. Ocking, A. P. Cote, J. Kim, O. M. Yaghi (2005). "Design, Synthesis, Structure, and Gas (N2, Ar, CO2,CH4, and H2) Sorption Properties of Porous Metal-Organic Tetrahedral and Heterocuboidal Polyhedra". J. Am. Chem. Soc. 127: 7110.doi:10.1021/ja042802q.

[95] T. F. Degnan (2003). "The implications of the fundamentals of shape selectivity for the development of catalysts for the petroleum andpetrochemical industries". J. Catal. 216: 32. doi:10.1016/S0021-9517(02)00105-7.

[96] A. Kuc, A. Enyashin, G. Seifert (2007). "Metal−Organic Frameworks: Structural, Energetic, Electronic, and Mechanical Properties". J.Phys. Chem. B 111: 8179. doi:10.1021/jp072085x.

[97] A. Esswein, D. Nocera (2007). "Hydrogen Production by Molecular Photocatalysis". Chem. Rev. 107: 4022. doi:10.1021/cr050193e.[98] C. Yang, M. Messerschmidt, P. Coppens, M. A. Omary (2006). "Trinuclear Gold(I) Triazolates: A New Class of Wide-Band Phosphors and

Sensors". Inorg. Chem. 45: 6592. doi:10.1021/ic060943i.[99] M. Fuentes-Cabrera, D. M. Nicholson, B. G. Sumpter, M. Widom (2005). "Electronic structure and properties of isoreticular metal-organic

frameworks: The case of M-IRMOF1 (M = Zn, Cd, Be, Mg, and Ca)". J. Chem. Phys. 123: 124713. doi:10.1063/1.2037587.[100] J. Gascon, M. D. Hernμndez-Alonso, A. R. Almeida, G. P. M. van Klink, F. Kapteijn, G. Mul (2008). "Isoreticular MOFs as Efficient

Photocatalysts with Tunable Band Gap: An Operando FTIR Study of the Photoinduced Oxidation of Propylene". Chem. Sus.Chem. 1: 981.doi:10.1002/cssc.200800203.

[101] Mendoza-Cortes JL; Han SS; Furukawa H; Yaghi OM; Goddard, WA; Adsorption Mechanism and Uptake of Methane in Covalent OrganicFrameworks: Theory and Experiment. J. Phys. Chem. A, 2010, 114, pp 10824–10833.DOI: 10.1021/jp1044139

[102] Mendoza-Cortes, JL; Pascal, TA; Goddard, WA; Design of Covalent Organic Frameworks for Methane Storage. J. Phys. Chem. A, 2011,115, pp 13852–13857.DOI: 10.1021/jp209541e

External links• MOF pore characterizations (http:/ / helios. princeton. edu/ mofomics/ )• Hypothetical MOFs Database (http:/ / hmofs. northwestern. edu/ hc/ crystals. php)

Article Sources and Contributors 20

Article Sources and ContributorsMetal-organic framework  Source: http://en.wikipedia.org/w/index.php?oldid=510059780  Contributors: Chem511grp3f09, Chessphoon, Chris the speller, Chriswaterguy, DMacks, DavidKay,Denzil Simoes, Furmanj, Gene Nygaard, Glmccolm, GoingBatty, Januskropp, Kt57, LilHelpa, Loco doug, Lrohrstrom, Materialscientist, Mexicanoscientificos, Mihai, Molestash, Palacantona7,Rjwilmsi, Rotational, Schmloof, SchreiberBike, Sikkema, Smokefoot, Tmangray, V8rik, WAS 4.250, WikHead, William Avery, 56 anonymous edits

Image Sources, Licenses and ContributorsFile:Oxalic acid.png  Source: http://en.wikipedia.org/w/index.php?title=File:Oxalic_acid.png  License: GNU Free Documentation License  Contributors: User:JrockleyFile:Malonic acid structure.png  Source: http://en.wikipedia.org/w/index.php?title=File:Malonic_acid_structure.png  License: Public Domain  Contributors: Edgar181File:Succinic acid.png  Source: http://en.wikipedia.org/w/index.php?title=File:Succinic_acid.png  License: Creative Commons Attribution-ShareAlike 3.0 Unported  Contributors: D.328 09:20,17 May 2006 (UTC)File:Glutaric acid.png  Source: http://en.wikipedia.org/w/index.php?title=File:Glutaric_acid.png  License: Public Domain  Contributors: Edgar181, InfoCanFile:Phthalic-acid-2D-skeletal.png  Source: http://en.wikipedia.org/w/index.php?title=File:Phthalic-acid-2D-skeletal.png  License: Public Domain  Contributors: Benjah-bmm27File:Isophthalic-acid-2D-skeletal.png  Source: http://en.wikipedia.org/w/index.php?title=File:Isophthalic-acid-2D-skeletal.png  License: Public Domain  Contributors: Benjah-bmm27File:Terephthalic-acid-2D-skeletal.png  Source: http://en.wikipedia.org/w/index.php?title=File:Terephthalic-acid-2D-skeletal.png  License: Public Domain  Contributors: Benjah-bmm27, JyntoFile:Zitronensäure - Citric acid.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Zitronensäure_-_Citric_acid.svg  License: Public Domain  Contributors: NEUROtikerFile:Trimesic acid.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Trimesic_acid.svg  License: Public Domain  Contributors: FvasconcellosFile:1,2,3-triazole numbering.png  Source: http://en.wikipedia.org/w/index.php?title=File:1,2,3-triazole_numbering.png  License: Public Domain  Contributors: Original uploader was Edgar181at en.wikipediaFile:1,2,4-triazole numbering.png  Source: http://en.wikipedia.org/w/index.php?title=File:1,2,4-triazole_numbering.png  License: Public Domain  Contributors: Original uploader was Edgar181at en.wikipediaFile:Squaric acid.png  Source: http://en.wikipedia.org/w/index.php?title=File:Squaric_acid.png  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Benjah-bmm27,Physchim62File:IRMOF-1 wiki.png  Source: http://en.wikipedia.org/w/index.php?title=File:IRMOF-1_wiki.png  License: Public Domain  Contributors: Tony BoehleFile:Zeolite-ZSM-5-3D-vdW.png  Source: http://en.wikipedia.org/w/index.php?title=File:Zeolite-ZSM-5-3D-vdW.png  License: Public Domain  Contributors: Benjah-bmm27, Chris.urs-o,JyntoFile:MOFscat3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:MOFscat3.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:Jakoch1000

LicenseCreative Commons Attribution-Share Alike 3.0 Unported//creativecommons.org/licenses/by-sa/3.0/