Porous Materials -Metal-Organic Frameworks

2012 Nanocamp NCMN, UNL

Dr. Jian Zhang & Jacob Johnson

Department of Chemistry

What does a chemist do?

• Chemists observe and study

• Chemists study the composition, assembly, properties, and reactivity of matter (atoms, molecules, materials)

• Chemistry is considered as the central science

Chemistry is the Central Science

Chemistry

Medicine

Environmental Sciences

Astronomy

Biology

Geology

Physics Materials Science

Pharmaceutical

What does a chemist do?

• Chemists make compounds and materials

– Synthetic chemistry

• Measure properties of materials

– Analytical chemistry

• Model chemical reactions and materials structures

– Theoretical and computational

chemistry

Penicillin

What does it take to become a chemist?

• Strong interest in science • Strong academic performance • 4+ years of college • Graduate degree (2-4 years)

– Hundreds of graduate schools in the US

• Diverse and rewarding career – Creativity is important – Worldwide industry – Work on important global problems

• Energy • Pollution • Disease

The Zhang’s Group Research

Metal-organic Frameworks Covalent-organic Frameworks Porous polymer networks

Porous Materials in Nature

Sandstones

Sea Sponge

Butterfly Wings

Egg Shells Snow

Coral Soil Bone Lungs

Lemons

Artificial Porous Materials

Insulation

Cake

Concrete

Bread Ceramics

Chalk Brick Paper

Sponges

Clothing

Pore Type (size)

Micropores (< 2 nm) Mesopores (2-50 nm) Macropores (< 50 nm)

Surface of a chicken egg shell Carbon membrane Monolithic column

Microporous Materials

• A microporous material is a material containing pores with diameters less than 2 nm

• Activated Carbons

• Zeolites

• Metal-organic frameworks

• Covalent organic frameworks

• Microporous polymer

Applications

– Microporous materials • Activated carbons

– The small size of their pores gives them great surface area… they can adsorb a large amount of gas directly on to their surface. Popular support for some catalyst metals (especially palladium and platinum). ρ~ 2g/cm3

• Zeolites – The narrow size distribution of their pores makes them very useful

for gas separation. Also used as catalysts because of acid sites in the pores. ρ~ 4g/cm3

• Metal organic frameworks – Their huge surface area and pore volume makes them potentially

useful for gas sequestration/storage. ρ< 0.5g/cm3

Activated Carbons

Rice Husk Nut Shells

Coconut Fiber Biomass

Made from a variety of materials:

Organic, non-ordered structure

Zeolites – Micropores are part of their crystal structure:

• Most are synthetic

• Alumino-silicates

• Silicalite = no aluminum

• Cation can be H+, Na+, Ca2+, NH4+, etc

• Pore shape needs to be incorporated into pore size calculation for accurate results

• Some adsorbates are better than others

Inorganic, ordered structure

Metal Organic Frameworks MOFs

– Synthetic materials

– Also called coordination polymers

– Similar materials without metals are called COFs… covalent coordination polymers

– Still a very active research area

Inorganic-Organic Hybrid, ordered structure

Metal Organic Frameworks MOFs

Zn4O tetrahedra (blue) are joined by organic linkers (O, red, C, black), giving an extended 3D cubic framework with inter-connected pores of 11.2 Å aperture width and 18.5Å pore (yellow sphere) diameter

Metal Organic Frameworks MOFs

Breathable MOFs

• Petroleum dependence → U.S. imports 55% of its oil expected to grow to 68% in 2025 • Hydrogen as energy carrier → clean, efficient, and can be derived from domestic resources

Renewable (biomass, hydro, wind, solar, and geothermal)

Fossil fuels (coal ,natural gas, etc.)

Nuclear Energy

Hydrogen storage

Hydrogen Storage in Nano-Porous Materials

• Hydrogen storage is a critical enabling technology for the acceptance of hydrogen powered vehicles • Storing sufficient hydrogen on board to meet consumers requirements (eg. driving range, cost, safety, and performance) is a crucial technical parameter • No approach currently exists that meets technical requirement. (driving range > 300 miles)

• U.S. DoE → develop on board storage systems achieving 6 and 9 wt% for 2010 and 2015

Hydrogen storage

Hydrogen Storage in Nano-Porous Materials

Current Challenges with H2 Storage Options

Compressed Hydrogen -High pressure (500-700 atm), -Expensive storage container Liquid Hydrogen -Expensive cooling system required -High energy cost to liquefy H2

Complex and Metal Hydrides -Poor reversibility -Require high temperature and pressure (>100 ˚C and >100 atm)

MOFs as hydrogen storage materials

~ 3% wt @ 77 K, 1 atm

CO2 Sequestration

MOFs as CO2 storage materials

38.5 wt% @ 273 K, 1 atm

MOF Construction

Organic Linkers Metal Nodes

Mn2+

109.5° 90° 90°

120°

Tetrahedral Octahedral Trigonal Bipyrimidal