www.sciencemag.org/cgi/content/full/339/6116/193/DC1

Supplementary Materials for

Shape-Memory Nanopores Induced in Coordination Frameworks by Crystal Downsizing

Yoko Sakata, Shuhei Furukawa,* Mio Kondo, Kenji Hirai, Nao Horike, Yohei Takashima, Hiromitsu Uehara, Nicolas Louvain, Mikhail Meilikhov, Takaaki Tsuruoka,

Seiji Isoda, Wataru Kosaka, Osami Sakata, Susumu Kitagawa*

*To whom correspondence should be addressed. E-mail: shuhei.furukawa@icems.kyoto-u.ac.jp (S.F.); kitagawa@icems.kyoto-u.ac.jp (S.K.)

Published 11 January 2013, Science 339, 193 (2013)

DOI: 10.1126/science.1231451

This PDF file includes:

Materials and Methods Supplementary Text Figs. S1 to S61 Table S1 Full Reference List

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Table of Contents SECTION 1 : Crystal Downsizing of [Cu2(bdc)2(bpy)]n (1)

Pages

• Materials and Methods

4-7

• Schematic Illustration of Two Types of Flexible PCPs (Fig. S1)

8

• Single Crystal Structures of [Cu2(bdc)2(bpy)]n (Fig. S2)

9

• SEM Images of [Cu2(bdc)2(bpy)]n (1) Crystals (Fig. S3)

10

• Size-Distribution of [Cu2(bdc)2(bpy)]n (1) Crystals Obtained from TEM Images (Fig. S4)

11

• Thickness Evaluation of Plate-like Meso-Sized Crystals by Scherrer’s Equation (Fig. S5)

12

• Summary of Crystal Size of [Cu2(bdc)2(bpy)]n (1) (Table S1)

13

• Electron Diffraction Pattern of 1-meso50 (Fig. S6)

14

• PXRD Patterns of DMF Immersed [Cu2(bdc)2(bpy)]n (1) Crystals (Fig. S7)

15

• Thermogravimetric Analysis of [Cu2(bdc)2(bpy)]n (1) Crystals (Fig. S8-S19)

16-27

• Variable Temperature XRD of the Open Dried 1-meso50 (Fig. S20-S21)

28

• DSC measurement of the Open Dried 1-meso50 (Fig. S22)

29

• Reversible Phase Transition between the Open Dried 1-meso50 and the Closed 1-meso50 (Fig. S23)

30

• Full Chart of Methanol Adsorption Isotherms of the Closed Phase of [Cu2(bdc)2(bpy)]n (1) Crystals (Fig. S24-S29)

31-36

• Experimental Apparatus of XRD Measurement under Methanol Humidity Control (Fig. S30)

37

• XRD Measurement of the Closed 1-mico, the Closed 1-meso50, and the Open Dried 1-meso50 under Methanol Humidity Control (Fig. S31-S33)

38-40

• Full Chart of Switchable Methanol Adsorption Isotherms of 1-meso50 (Fig. S34-S36)

41-43

• Repeatability of the Open–Closed–Open Phase Transition of 1-meso50 (Fig. S37-S39)

44-46

• Carbon Dioxide (CO2) Adsorption Isotherms of [Cu2(bdc)2(bpy)]n (1) Crystals (Fig. S40-S42)

47-49

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SECTION 2: Crystal Downsizing of [Cu2(bdc)2(bpe)]n (2)

Pages

• Single Crystal Structures of [Cu2(bdc)2(bpe)]n (2) (Fig. S43)

50

• TEM Images of [Cu2(bdc)2(bpe)]n (2) Crystals (Fig. S44)

S1

• Size-Distribution of [Cu2(bdc)2(bpe)]n (2) Crystals Obtained from TEM Images (Fig. S45)

52

• SEM Images of [Cu2(bdc)2(bpe)]n (2) Crystals (Fig. S46)

53

• PXRD Patterns of Ethanol Immersed [Cu2(bdc)2(bpe)]n (2) Crystals (Fig. S47)

54

• PXRD Patterns of Completely Dried [Cu2(bdc)2(bpe)]n (2) Crystals (Fig. S48)

55

• Thermogravimetric Analysis of [Cu2(bdc)2(bpe)]n (2) Crystals (Fig. S49-S56)

56-63

• PXRD Measurement of [Cu2(bdc)2(bpe)]n (2) Crystals Before and After Thermal Treatment (Fig. S57)

64

• Reversible Phase Transition between the Open Dried 2-meso700 and the Closed 2-meso700 (Fig. S58)

65

SECTION 3: Discussion about Why the Open Dried Phase was Isolated By Crystal Downsizing of Flexible PCPs

• Illustration of The Plausible Energy Diagram between the Open Dried Phase and The Closed Phase (Fig. S59)

66

• Comparison of Hysteretic Loop Width of Methanol Adsorption Isotherms between 1-micro and 1-meso300 (Fig. S60).

67

• Schematic Illustration of Multiple Nucleation and Growth Mechanism in Phase Transition (Fig. S61)

68

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SECTION 1: Crystal Downsizing of [Cu2(bdc)2(bpy)]n (1)

Materials and Methods Materials

Reagents and solvents were purchased from commercial sources and used without further purification. Micrometer-sized crystals (1-micro) were synthesized according to the literature (13).

Preparation of Single Crystal of [Cu2(bdc)2(bpy)]n (1)

Cu(ClO4)2·6H2O (1 mmol, 370 mg), Na2bdc (1 mmol, 210 mg), and bpy (0.5 mmol, 78 mg) were dissolved in 100 mL of water, 50 mL of 1:1 mixture of water and ethanol, 50 mL of 1:2 mixture of water and ethanol, respectively. 2 mL of Cu(II) solution was slowly and sequentially layered with 1 mL of Na2bdc solution and 1 mL of bpy solution using 1 mL buffter (2:1 mixture of water and ethanol) and kept at 40 °C. Green square-block-shaped crystals were obtained after 2 weeks. The crystal was separated and washed with an ethanol (1⊃ethanol) and replaced with DMF or MeOH (1⊃DMF or 1⊃methanol). The crystals of methanol incorporated 1 was dried in a vacuum for 30 min, resulting in a dried sample, 1.

Preparation of Single Crystal of [Cu2(bdc)2(bpe)]n (2)

Cu(ClO4)2·6H2O (1 mmol, 370 mg) was dissolved in 100 mL of water, and an aqueous solution (50 mL) of Na2bdc (1 mmol, 210 mg) was mixed with an ethanolic solution (50 mL) of bpe (0.5 mmol, 91 mg). 2 mL of Cu(II) solution was slowly layered with 2 mL of mixed-ligand solution using 1 mL buffter (2:1 mixture of water and ethanol) and kept at 25 °C. Green square-block-shaped crystals were obtained after 2 weeks. The crystal was separated and washed with an ethanol (2⊃ethanol). Preparation of Meso-Sized Crystals of [Cu2(bdc)2(bpy)]n (1-meso50-300)

A methanol solution (32 mL) of terephthalic acid (33.6 mg) was immediately added to a methanol solution (12.5 mL) of Cu(OAc)2·H2O (40 mg) and acetic acid (115, 230, 345, 460, 575 µL for r = 10, 20, 30, 40, and 50, respectively). After the mixture was allowed to stand for 3 days at room temperature, a methanol solution (10 mL) of bpy (15.6 mg) was added to the mixture, which was then allowed to react at room temperature for 2 days. A yellow green precipitate was collected, washed with methanol by three dispersion-sonication-centrifugation cycles, and dried at room temperature under a vacuum. Preparation of Micrometer-Sized Crystals of [Cu2(bdc)2(bpe)]n (2-micro)

A methanol solution (200 mL) of CuSO4·5H2O (310 mg) was immediately added to a methanol solution (200 mL) of terephthalic acid (210 mg) and formic acid (1.5 mL). After the mixture was allowed to stand for 3 days at 40 °C, the resulting blue precipitate was collected by centrifugation and transferred to a round bottle flask. After the addition of methanol (30 mL), bpe (115 mg) was added to the mixture, which was then allowed to react at room temperature for 2 days. A yellow green precipitate was collected, washed

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with methanol by three dispersion-sonication-centrifugation cycles, and dipped with dichloromethane for 12 hrs and dried at 70 °C under a vacuum. Preparation of Meso-Sized Crystals of [Cu2(bdc)2(bpe)]n (2-meso50, 300, 700)

A methanol solution (32 mL) of terephthalic acid (33.6 mg) was immediately added to a methanol solution (12.5 mL) of Cu(OAc)2·H2O (40 mg) and acetic acid (115, 575, 863 µL for r = 10, 50, and 75, respectively). After the mixture was allowed to stand for 3 days at room temperature, a methanol solution (10 mL) of bpe (18.0 mg) was added to the mixture, which was then allowed to react at room temperature for 2 days. A yellow green precipitate was collected, washed with methanol by three dispersion-sonication-centrifugation cycles, and dipped with dichloromethane for 12 hrs and dried at 70 °C under a vacuum. Single Crystal Analysis of [Cu2(bdc)2(bpy)]n (1) and [Cu2(bdc)2(bpe)]n (2)

Single crystals of [Cu2(bdc)2(bpy)]n and [Cu2(bdc)2(bpe)]n were mounted in a loop. Measurements were taken using a Rigaku AFC10 diffractometer using a Rigaku Saturn CCD system (Rigaku) equipped with a rotating anode X-ray generator that produced multilayer mirror monochromated MoKα radiation. In all cases, the structure was elucidated using direct methods and refined using full-matrix least-squares techniques on F2 (SHELXL-97 (27)). All of the non-hydrogen atoms were anisotropically refined, whereas all hydrogen atoms were placed geometrically and refined using a riding model with Uiso constrained to be 1.2 times Ueq of the carrier atom. The diffused electron densities resulting from residual solvent molecules were removed from the data set using the SQUEEZE routine of PLATON and refined further using the data generated.

Crystal data for 1⊃ethanol: C26H16Cu2N2O8 (the contribution of the disordered guest molecules is not included in the derived data), Mr = 611.49, triclinic, space group P¯1, (#2), a = 10.8111(11), b = 10.8475(11), c = 14.0210(15) Å, α = 87.531(3), β = 89.039(3), γ = 85.997(2)°, V = 1638.6(3) Å3, Z = 2, T = 203(2) K, ρcalcd = 1.239 gcm-3, µ(Mo-Kα) = 1.339 cm-1, 2θmax = 50.0°, λ(Mo-Kα) = 0.71075 Å, 11311 reflections measured, 5668 unique, 4411 (I > 2σ(I)) were used to refine 380 parameters, 66 restrains, wR2 = 0.0954, R1 = 0.0306 (I > 2σ(I)), GOF = 1.12.

Crystal data for 1⊃DMF: C52H32Cu4N4O16 (the contribution of the disordered guest molecules is not included in the derived data), Mr = 1222.98, triclinic, space group P¯1, (#2), a = 10.8044(16), b = 14.053(2), c = 21.678(3) Å, α = 89.878(3), β = 83.363(4), γ = 88.981(4)°, V = 3268.8(9) Å3, Z = 2, T = 203(2) K, ρcalcd = 1.243 gcm-3, µ(Mo-Kα) = 1.342 cm-1, 2θmax = 50.0°, λ(Mo-Kα) = 0.71075 Å, 22025 reflections measured, 11253 unique, 7492 (I > 2σ(I)) were used to refine 722 parameters, 48 restrains, wR2 = 0.1133, R1 = 0.0369 (I > 2σ(I)), GOF = 1.056.

Crystal data for 1⊃methanol: C52H32Cu4N4O16 (the contribution of the disordered guest molecules is not included in the derived data), Mr = 1222.98, triclinic, space group P¯1, (#2), a = 10.8195(18), b = 14.004(3), c = 21.682(4) Å, α = 87.570(4), β = 86.557(5), γ = 88.083(5)°, V = 3274.9(10) Å3, Z = 2, T = 203(2) K, ρcalcd = 1.24 gcm-3, µ(Mo-Kα) = 1.34 cm-1, 2θmax = 50.0°, λ(Mo-Kα) = 0.71075 Å, 22612 reflections measured, 11317 unique, 6956 (I > 2σ(I)) were used to refine 722 parameters, 0 restrains, wR2 = 0.1156, R1 = 0.0458 (I > 2σ(I)), GOF = 0.95.

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Crystal data for 1: C13H8CuNO4, Mr = 305.74, triclinic, space group P¯1, (#2), a = 7.898(3), b = 8.930(3), c = 10.818(3) Å, α = 67.509(12), β = 80.401(14), γ = 79.566(13)°, V = 689.3(4) Å3, Z = 2, T = 203(2) K, ρcalcd = 1.473 gcm-3, µ(Mo-Kα) = 1.591 cm-1, 2θmax = 50.0°, λ(Mo-Kα) = 0.71075 Å, 4618 reflections measured, 2368 unique, 2209 (I > 2σ(I)) were used to refine 172 parameters, 0 restrains, wR2 = 0.0881, R1 = 0.033 (I > 2σ(I)), GOF = 1.127.

Crystal data for 2⊃ethanol: C28H18Cu2N2O8 (the contribution of the disordered guest molecules is not included in the derived data), Mr = 637.52, triclinic, space group P¯1, (#2), a = 10.806(2), b = 10.834(2), c = 16.270(4) Å, α = 90.492(4), β = 97.154(4), γ = 90.855(4)°, V = 1889.6(7) Å3, Z = 2, T = 203(2) K, ρcalcd = 1.12 gcm-3, µ(Mo-Kα) = 1.163 cm-1, 2θmax = 50.0°, λ(Mo-Kα) = 0.71073 Å, 13101 reflections measured, 6561 unique, 5143 (I > 2σ(I)) were used to refine 398 parameters, 61 restrains, wR2 = 0.1444, R1 = 0.0417 (I > 2σ(I)), GOF = 1.101. Transmission Electron Microscopy

The TEM observations were performed with a JEOL JEM-1400 transmission electron microscopy (TEM) system operating at 120 kV. The TEM samples were prepared by dispersing the precipitates in THF, followed by depositing the solution dropwise onto a carbon-coated TEM grid. The size and its distribution of nanocrystals were measured using calibrated TEM images by ImageJ software (a public domain image processing and analysis program). For each sample, 300-500 particles were measured for the statistical size distribution analysis. Field-Emission Scanning Electron Microscopy

Scanning electron microscopy (SEM) observations were performed with a JEOL JSM-7001F4 SEM system operating at 5.0, 15.0, and 25.0 kV. Dried powder samples were deposited on carbon tape and coated with osmium prior to measurement. Methanol and Carbon Dioxide Sorption Measurement

The sorption isotherms of [Cu2(bdc)2(bpy)]n for methanol at 298 K (or 303 K) and CO2 at 195 K were recorded on a BELSORP-max volumetric-adsorption instrument from BEL Japan, Inc. All measurements were performed using the samples after pretreatment at room temperature under vacuum conditions for 12 h. Powder X-ray Diffraction Measurement

The diffraction data were collected on a Bruker Model D8 Discover apparatus with GADDS equipped with a sealed tube X-ray generator producing Cu Kα radiation.

The diffractions for the Sherrer equation and variable temperature measurements were collected using Smart Lab (Rigaku) equipped with a rotating anode Cu Kα X-ray generator. The measurements of the diffractions data for the Sherrer equation were performed in the theta/2 theta out-of-plane mode (2 theta = 3-12°) with a step-size of 0.01°for 2 theta and a scan-rate of 0.02° s–1 for 2 theta. The variable temperature XRD measurement were collected with Anton Paar DCS 350 sample holder connected with TCU 100 temperature control unit, and LNC nitrogen suction equipment. It was performed in the theta/2 theta out-of-plane mode (2 theta = 5-20°) with a step-size of 0.02°for 2 theta and a scan-rate of 0.01° s–1 for 2 theta.

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Thermogravimetric Analysis The analysis was performed using a Rigaku Model Thermo Plus TG 8120 apparatus

in the temperature range of 298-773 K under a nitrogen atmosphere, at a heating rate of 5 K min–1. Electron Diffraction Crystallography

Electron diffraction patterns were taken with a scanning transmission electron microscope (JEM-2200FS) at an accelerating voltage of 200 kV. To obtain selected-area electron diffraction patterns, samples were placed on an electron microscopic micro grid reinforced by an amorphous carbon film. The relation between crystallographic orientation and morphology was estimated from the diffraction net pattern and corresponding image.

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Schematic Illustration of Two Types of Flexible PCPs Structural transformability in flexible PCPs can be categorized into two different

classes (Fig. S1). In the first-order phase transition-like transformability (Eq.1), the original (Ao) and deformed (Ad⊃nG) phases, contribute to the guest (G) sorption process, and gate-type abrupt sorption behavior and hysteresis are observed when a threshold concentration is achieved (28). In contrast, in the second-order phase transition-like transformability (Eq.2), multiple intermediate states (A2, A3, etc) corresponding to partial molecular accommodation coexist with the two phases, and gradual uptake without hysteresis is observed (29).

Ao + nG ⇄ Ad⊃nG (Eq.1) Ao + nG ⇄ A2⊃G + (n-1)G ⇄ A3⊃2G + (n-2)G ⇄ ··· ⇄ Ad⊃nG (Eq.2)For the induction of the shape memory effect in flexible PCPs, the prerequisites are

the isolation of the deformed metastable phase without incorporated guests (Ad), and a healing process that forms the original phase (Ao) in the presence of stimulus (also known as pseudoelasticity). Therefoere, we focused on [Cu2(bdc)2(bpy)]n as a former class of material because in general crystalline solids that participate in first-order phase transitions with high cooperativity generate a metastable phase.

Fig. S1. Schematic Illustration of two types of flexible PCPs; (A) flexible PCPs with the first-order phase transition-like transformability, (B) flexible PCPs with the second-order phase transition-like transformability.

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Single Crystal Structure of [Cu2(bdc)2(bpy)]n Comparison of the structures for, ethanol immersed [Cu2(bdc)2(bpy)]n (1⊃ethanol),

methanol immersed [Cu2(bdc)2(bpy)]n (1⊃methanol), DMF immersed [Cu2(bdc)2(bpy)]n

(1⊃DMF), and dried [Cu2(bdc)2(bpy)]n (1) was shown in Fig. S4. Regardless of a kind of guest molecules, they showed similar structures when guest molecules are accommodated in the pore (Fig. S2A-C). In contrast, as we described in the main text, the structure shared drastically to minimize the pore in the absence of guest molecule (Fig. S2D).

Fig. S2. Comparison of crystal structures of [Cu2(bdc)2(bpy)]n ; (A) 1⊃ethanol, (B) 1⊃methanol, (C) 1⊃DMF, (D) 1.

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SEM Images of [Cu2(bdc)2(bpy)]n (1) Crystals Plate-like crystals with the similar size obtained from TEM image were observed

even by SEM images. From these images, the thickness of the plate-like meso-sized crystal could be roughly evaluated. With the increase of the size of the crystals, the thickness also increased from ca.10 nm (1-meso50) to 35 nm (1-meso300). The crystal dimension of micrometer-sized crystal was determined as 5 µm × 5 µm × 500 nm.

Fig. S3. SEM images of meso-sized and micrometer-sized crystals of 1; (A) 1-meso50, (B) 1-meso60, (C) 1-meso110, (D) 1-meso160, (E) 1-meso300, (F) 1-micro.

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Size-Distribution of [Cu2(bdc)2(bpy)]n (1) Crystals Obtained from TEM Images

Fig. S4. Size-distribution of meso-sized crystals obtained from TEM images; (A) 1-meso50, (B) 1-meso60, (C) 1-meso110, (D) 1-meso160, (E) 1-meso300.

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Thickness Evaluation of Plate-like Meso-Sized Crystals by Sherrer’s Equation Because statistical study for the thickness of the crystals from SEM image is quite

difficult, those are also evaluated by applying the broadness of the XRD peak to Scherrer’s equation. The instrumental peak broadening was determined using a silicon reference standard (NIST 640d).

D = K·λ / βcosθ (D : crystal domain size, K : Scherrer constant, β : peak width) (010) Bragg reflection at 2θ = 6.29° of DMF accommodated crystal (1⊃DMF) was

used for the evaluation of the crystal domain size of the plate-like crystals (1-meso50 to 1-meso300). As clearly shown in Fig. S5, the crystal thickness is correlated with the crystal width obtained from TEM images.

Fig. S5. Thickness estimated from Scherrer’s equation versus width of the plate-like meso-sized crystals.

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Summary of Crystal Size of [Cu2(bdc)2(bpy)]n (1) The crystal size of each samples obtained from SEM (Fig. S5), TEM (Fig. 3A-E, Fig.

S4), and Scherrer’s equation (Fig. S5) was summarized in Table S1. By the comparison between these crystal size data and observed behavior (elastic PCP or shape memory PCP) in XRD under complete dried condition (Fig. 3G), it was clarified that the unusual “open dried phase” could be isolated when the crystal width is less than 100 nm (i.e. mesoscale).

Table S1. Summary of crystal size of each crystals and corresponding observed phase. sample crystal width crystal thickness observed behavior

1-meso50 45 ± 13 nma 19 nmc mainly shape memory PCP

1-meso60 62 ± 15 nma 20 nmc mainly shape memory PCP

1-meso110 108 ± 28 nma 23 nmc shape memory PCP and elastic PCP

1-meso160 156 ± 38 nma 25 nmc shape memory PCP and elastic PCP

1-meso300 296 ± 56 nma 26 nmc elastic PCP

1-micro 5 µmb 500 nmb elastic PCP aobtained from TEM images, b obtained from SEM images, cobtained from Sherrer’s equation,

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Electron Diffraction Pattern of 1-meso50 In order to reveal the correlation between anisotropic crystal morphology and

framework system, electron diffraction pattern of individual meso-sized crystal (1-meso50) was investigated. The diffraction pattern can be indexed by “the open dried phase” isomorphic to the open phase of 1⊃DMF. The TEM image of Fig. S6A shows plate-like crystals. The corresponding diffraction pattern in Fig. S6B can be indexed with a net-pattern on the a*c*-plane of an isomorphic structure of 1⊃DMF, indicating that the pattern is projected along the b-axis of the crystal. Then the lateral directions of plate-like crystal are the a- and c- axes, and the thickness direction is the b-axis which is the Cu-N coordination direction of the framework. These results also indicated that coordination modulation step determines the crystal width of the resulting plate-like crystal.

Fig. S6. (A) TEM image of 1-meso50, (B) the corresponding selected-area electron diffraction pattern taken from a specimen area of 100 nm in diameter, and (C) orientation of the platelet nanocrystal estimated from the electron diffraction data. The white circle in (A) shows the selected area to form the diffraction pattern in (B). The diffraction pattern can be indexed with the b-axis projection (net-pattern on a*c*-plane) of open isomorphic structure such as 1⊃DMF

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PXRD Patterns of DMF Immersed [Cu2(bdc)2(bpy)]n (1) Crystals DMF immersed every crystal showed PXRD patterns corresponding to the simulated

pattern obtained from single crystal structure of 1 DMF, indicating that [Cu2(bdc)2(bpy)]n (1) framework was obtained as a pure phase in every condition.

Fig. S7. PXRD patterns of DMF immersed [Cu2(bdc)2(bpy)]n (1) crystals (open phase); (A) 1-meso50, (B) 1-meso60, (C) 1-meso110, (D) 1-meso160, (E) 1-meso300, and (F) 1-micro, (G) simulated pattern of 1⊃DMF (the open phase), (H) simulated pattern of 1 (the closed phase).

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Thermogravimetric Analysis of [Cu2(bdc)2(bpy)]n (1) Crystals Completely dried every crystal showed almost no weight loss before decomposition

(Fig. S8-S13). The small amount of weight loss in small crystals, is probably due to the larger surface contribution of the release of solvent from surface, but not from the pore. In contrast, DMF immersed every crystals showed the similar weight loss up to 150 °C, indicating that the crystallinity did not decrease drastically even by crystal downsizing (Fig. S14-S19).

Fig. S8. TG analysis of dried 1-micro (the closed phase).

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Fig. S9. TG analysis of dried 1-meso50 (mainly open phase).

18

Fig. S10. TG analysis of dried 1-meso60 (mainly open phase).

19

Fig. S11. TG analysis of dried 1-meso110 (a mixture of the open and the closed phase).

20

Fig. S12. TG analysis of dried 1-meso160 (a mixture of the open and the closed phase).

21

Fig. S13. TG analysis of dried 1-meso300 (the closed phase).

22

Fig. S14. TG analysis of DMF included 1-micro.

23

Fig. S15. TG analysis of DMF included 1-meso50.

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Fig. S16. TG analysis of DMF included 1-meso60.

25

Fig. S17. TG analysis of DMF included 1-meso110.

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Fig. S18. TG analysis of DMF included 1-meso160.

27

Fig. S19. TG analysis of DMF included 1-meso300.

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Variable Temperature XRD of the Open Dried 1-meso50 Upon heating, the structural change from the open dried 1-meso50 to the closed 1-

meso50 was observed. Because either “the open phase” or “the closed phase” could be observed during the transformation, this phase transition is classified as a first-order phase transition (Fig. S20). The open dried 1-meso50 did not regenerate after cooling the obtained closed 1-meso50 to room temperature (Fig. S21), indicating that the closed phase is thermodynamically more stable than the open phase.

Fig. S20.Variable Temperature XRD of the open dried 1-meso50 (from 293 K to 473 K).

Fig. S21. XRD patterns of the open dried 1-meso50 before and after heating.

29

DSC Measurement of the Open Dried 1-meso50 Differential scanning calorimetry (DSC) was carried out with TA instruments DSC

Q2000 equipped with T zero cell and pressure regulator cell under Ar atomosphere. The sample was evacuated under vacuum for 30 min prior to the measurement in every cycle.

Fig. S22. DSC heating curves of the open dried 1-meso50. The heating rate of the measurements was 10 K min-1.

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Reversible Phase Transition between the Open Dried 1-meso50 and the Closed 1-meso50 Experimental Procedure

The open dried 1-meso50 was heated at 200 °C under vacuum condition for 1 h, and structural change to the closed 1-meso50 was confirmed by XRD measurement (Fig. S23B). After immersion to dehydrated methanol solution for 10 min, a yellow green precipitate was collected by centrifugations, and dried at room temperature under a vacuum for 2 h. Reproduction of the open dried 1-meso50 was confirmed by XRD (Fig. S23C) and TG measurement.

Fig. S23. PXRD of reversible phase change behavior of 1-meso50; (A) the open dried 1-meso50, (B) after heating at 200 °C of the open dried 1-meso50 (the closed 1-meso50), (C) dried after immersion of the closed 1-meso50 in methanol (the open dried 1-meso50), (D) simulated pattern of the closed phase of 1, (E) simulated pattern of DMF included the open phase of 1.

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Full Chart of Methanol Adsorption Isotherms of the Closed [Cu2(bdc)2(bpy)]n (1) Crystals

Fig. S24. Methanol adsorption isotherm (303 K) of the closed 1-micro.

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Fig. S25. Methanol adsorption isotherm (303 K) of the closed 1-meso50.

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Fig. S26. Methanol adsorption isotherm (303 K) of the closed 1-meso60.

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Fig. S27. Methanol adsorption isotherm (303 K) of the closed 1-meso110.

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Fig. S28. Methanol adsorption isotherm (303 K) of the closed 1-meso160.

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Fig. S29. Methanol adsorption isotherm (303 K) of the closed 1-meso300.

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Experimental Apparatus of XRD Measurement under Methanol Humidity Control In the environment-controlled synchrotron XRD system, the sample cell was

covered with the dome-shaped kapton film and the partial vapor pressure of methanol in helium carrier gas was adjusted by mass flow controllers. The controlled methanol vapor was carried out with 100 cc/min in the closed system. After increasing the methanol humidity, XRD was measured every 10 min. When the XRD pattern did not changed at all between before and after additional 10 min exposure of the vapor (i.e., the system reached to the equilibrium), the humidity was increased to the next point. This cycle was repeated until 50 % humidity for every sample (the closed 1-micro, the closed 1-meso50, the open dried 1-meso50).

Fig. S30. Experimental apparatus of XRD measurement under methanol humidity control; (A) sample cell, (B) whole apparatus.

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XRD Measurement of the Closed 1-micro, the Closed 1-meso50, and the Open Dried 1-meso50 under Methanol Humidity Control Closed 1-micro

Fig. S31. XRD measurement of the closed 1-micro under humidity control; (A) Methanol adsorption isotherm at 303 K of the closed phase of 1-meso50 (blue), 1-meso60 (turquoise), 1-meso110 (green), 1-meso160 (yellow), 1-meso300 (orange), and 1-micro (red). The arrows represent the pressure region in which the structural change from the closed phase to the open phase was observed for 1-micro (red) and 1-meso50 (blue). (B) Environmentally controlled XRD patterns of the closed 1-micro. Corresponding controlled partial vapor pressures are indicated in (A). From the point c to the point g (P/P0 = 0.10 – 0.17), the structural transformation from the non-porous closed phase to the porous open form was observed.

39

Closed 1-meso50

Fig. S32. XRD measurement of the closed 1-meso50 under humidity control; (A) Methanol adsorption isotherm at 303 K of the closed phase of 1-meso50 (blue), 1-meso60 (turquoise), 1-meso110 (green), 1-meso160 (yellow), 1-meso300 (orange), and 1-micro (red). The arrows represent the pressure region in which the structural change from the closed phase to the open phase was observed for 1-micro (red) and 1-meso50 (blue). (B) Environmentally controlled XRD patterns of the closed 1-meso50. Corresponding controlled partial vapor pressures are indicated in (A). From the point c to the point g (P/P0 = 0.14 – 0.30), the structural transformation from the non-porous closed phase to the porous open form was observed. Because no structural change was observed at lower region by environmentally controlled synchrotron XRD for the closed phase of 1-meso50, the adsorption at the low pressure region observed for meso-sized crystals is most likely attributed to the adsorption only on the crystal surface or the coordination of MeOH to Cu(II) open metal site on the crystal surface. Because of the larger crystal surface contribution for smaller meso-sized crystals, this effect became more obvious.

40

Open Dried 1-micro

The environmental-controlled measurements revealed that the open dried 1-meso50 showed almost no structural change during methanol adsorption. Probably because this sample contains a little amount of the closed 1-meso50 as observed by XRPD measurement of point a to c, the adsorption isotherm did not superimposed to desorption isotherm.

Fig. S33. XRD measurement of the open dried 1-meso50 under humidity control; (A) Methanol adsorption isotherm at 303 K of the open dried phase of 1-meso50. (B) Environmentally controlled XRD patterns of the open dried 1-meso50. Corresponding controlled partial vapor pressures are indicated in (A). The peak corresponding to the closed phase was indicated with asterisk.

41

Full Chart of Switchable Methanol Adsorption Isotherms of 1-meso50

Fig. S34. Methanol adsorption isotherm (298 K) of the open dried 1-meso50.

42

Fig. S35. Methanol adsorption isotherm (298 K) of the closed 1-meso50 (after heating up to 200 °C of the open dried 1-meso50).

43

Fig. S36. Methanol adsorption isotherm (298 K) of the reopened 1-meso50 (second cycle of adsorption isotherm measurement of the closed 1-meso50).

44

Repeatability of the Open-Closed-Open Phase Transition of 1-meso50 The reversible procedure of the open-closed-open 1-meso50 was repeated for twenty

times (Fig. S37). In every five cycle, XRD was measured and fully-evacuated form of the isolated open dried phase was confirmed by TG analysis (Fig. S38). From the XRD measurements, no significant degradation of the material was observed even after twenty cycles.

Fig. S37. PXRD of reversible phase change behavior of 1-meso50; (A) 1st cycle of the open dried 1-meso50, (B) 1st cycle of the closed 1-meso50, (C) 5th cycle of the open dried 1-meso50, (D) 5th cycle of the closed 1-meso50, (E) 10th cycle of the open dried 1-meso50, (F) 10th cycle of the closed 1-meso50, (G) 15th cycle of the open dried 1-meso50, (H) 15th cycle of the closed 1-meso50, (I) 20th cycle of the open dried 1-meso50, (J) 20th cycle of the closed 1-meso50.

45

Fig. S38. TG analysis of (A) 1st cycle of the open dried 1-meso50, (B) 5th cycle of the open dried 1-meso50, (C) 10th cycle of the open dried 1-meso50, (D) 15th cycle of the open dried 1-meso50, (E) 20th cycle of the open dried 1-meso50.

46

Fig. S39. Comparison of methanol adsorption isotherm (298 K) between the freshly synthesized open dried 1-meso50 and open dried 1-meso50 after five/twenty cycles of reversible open-closed-open phase transition. The adsorption isotherms of latter samples were superimposed over that of the initial open dried 1-meso50, indicating that the adsorption capacity did not change even after twenty cycles of reversible phase transformation.

47

Carbon Dioxide (CO2) Adsorption Isotherms of [Cu2(bdc)2(bpy)]n (1) Crystals CO2 adsorption isotherm of the closed 1-micro shows 2 step uptake around P/P0 =

0.01 and 0.1, respectively (Fig. S40). Because the former shows more drastic molecular uptake, it is probably attributed to the structural change from the closed form to the open form. The other smaller uptake is thought to be arising from the rearrangement of CO2 in the pores or local structural change such as rotating of the phenylene ring of the framework. In the case of the closed 1-meso50, the uptake at the gate-opening pressure shifted higher region and became more gradual compared to the closed 1-micro (Fig. S41). On the other hands, the adsorption isotherm of the open dried 1-meso50 shows Type-I uptake (Fig. S42). These tendencies are similarly observed when methanol was used as an adsorbate (see main text).

Fig. S40. CO2 adsorption isotherm (195 K) of the closed 1-micro.

48

Fig. S41. CO2 adsorption isotherm (195 K) of the closed 1-meso50.

49

Fig. S42. CO2 adsorption isotherm (195 K) of the open dried 1-meso50.

50

SECTION 2: Crystal Downsizing of [Cu2(bdc)2(bpe)]n (2)

Single Crystal Structure of [Cu2(bdc)2(bpe)]n As observed in [Cu2(bdc)2(bpy)]n (1), ethanol immersed [Cu2(bdc)2(bpe)]n

(2⊃ethanol) also gives isoreticular 2-fold interpenetrated structures (Fig. S43). Inter-framework π-π interactions between an aromatic ring of pyridine unit of one framework and terephthalic acid of another one was observed. Crystal 2⊃ethanol give longer c axis (16.27 Å) than crystal 1⊃ethanol ( c = 14.02 Å) (In this case, the c axis is parallel to the Cu-N coordination direction of the framework).

Fig. S43. Crystal structure of ethanol accommodated [Cu2(bdc)2(bpe)]n (2⊃ethanol).

51

TEM Images of [Cu2(bdc)2(bpe)]n (2) Crystals In every condition, plate-like crystals similar to 1-meso or 1-micro, were observed

by TEM images.

Fig. S44. TEM images of meso-sized and micrometer-sized crystals; (A) 2-meso50, (B) 2-meso300, (C) 2-meso700.

52

Size-Distribution of [Cu2(bdc)2(bpe)]n (2) Crystals Obtained from TEM Images The statistics of crystal width for ease plate-like crystal were investigated. Under

same modulation condition, crystals with almost same crystal width were obtained regardless of the kinds of amine pillar ligands (1 or 2). These results also indicated that the crystal width was controlled by first square grid formation step.

Fig. S45. Size-distribution of meso-sized crystals obtained from TEM images; (A) 2-meso50, (B) 2-meso300, (C) 2-meso700.

53

SEM Images of [Cu2(bdc)2(bpe)]n (2) Crystals Plate-like crystals were observed by SEM images, too. The observed thickness of

the crystal was ca. 20 nm for 2-meso50 and ca. 30 nm for 2-meso300. The crystal dimension of 2-meso700 and 2-micro were determined as 700 × 700 × 80 nm3 and 5 µm × 5 µm × 500 nm, respectively.

Fig. S46. SEM images of meso-sized and micrometer-sized crystals; (A) 2-meso50, (B) 2-meso300, (C) 2-meso700, (D) 2-micro.

54

PXRD Patterns of Ethanol Immersed [Cu2(bdc)2(bpe)]n (2) Crystals Ethanol immersed every crystal showed PXRD patterns corresponding to the

simulated pattern obtained from single crystal structure of 2 ethanol, indicating that [Cu2(bdc)2(bpy)]n (2) framework was obtained as a pure phase in every condition.

Fig. S47. PXRD patterns of ethanol immersed [Cu2(bdc)2(bpe)]n (2) crystals (the open phase); (A) 2-meso50, (B) 2-meso300, (C) 2-meso700, and (D) 2-micro, (E) simulated pattern of 2⊃ethanol (the open phase).

55

PXRD Patterns of Completely Dried [Cu2(bdc)2(bpe)]n (2) Crystals Completely dried crystal of 2 shows different structure depending on the crystal

sizes. Whereas the micrometer-sized crystal (2-micro) shows the closed phase, 2-meso50, 2-meso300, and 2-meso500 exhibit the open phase (Fig. S48). Because no weight loss was observed in every crystals before decomposition temperature (Fig. S49-51), it was elucidated that the open dried phase could be isolated when crystal size of 2 was downsized into 700 × 700 × 80 nm3 or less.

Fig. S48. PXRD patterns of completely dried [Cu2(bdc)2(bpe)]n (2) crystals; (A) simulated pattern of 2⊃ethanol (the open phase), (B) dried 2-meso50, (C) dried 2-meso300, (D) dried 2-meso700, and (E) dried 2-micro.

56

Thermogravimetric Analysis of [Cu2(bdc)2(bpe)]n (2) Crystals Completely dried every crystal showed almost no weight loss before decomposition

(Fig. S49-S52) even though 2-meso50, 2-meso300, and 2-meso700 give the open phase as observed in XRD measurement (Fig. S49). These results indicate that the open dried phase was successfully obtained in these cases. In contrast, DMF immersed every crystals showed the similar weight loss up to 150 °C, indicating that the crystallinity did not decrease drastically even by crystal downsizing (Fig. S53-S56).

Fig. S49. TG analysis of dried 2-micro (the closed phase).

57

Fig. S50. TG analysis of dried 2-meso50 (mainly the open phase).

58

Fig. S51. TG analysis of dried 2-meso300 (mainly the open phase).

59

Fig. S52. TG analysis of dried 2-meso700 (mainly the open phase).

60

Fig. S53. TG analysis of DMF included 2-micro.

61

Fig. S54. TG analysis of DMF included 2-meso50.

62

Fig. S55. TG analysis of DMF included 2-meso300.

63

Fig. S56. TG analysis of DMF included 2-meso700.

64

PXRD Measurement of of [Cu2(bdc)2(bpe)]n (2) Crystals Before and After Thermal Treatment

In order to investigate if these newly obtained the open dried phase in meso-sized crystals (2-meso50, 2-meso300, 2-meso700) could be converted to the closed phase by heating up at 200 °C, XRPD patterns were compared between before and after thermal treatment. Upon heating, almost no structural change was observed in the case of 2-meso50 or 2-meso300 (Fig. S57A-D). Only when the open dried 2-meso700 was heated up, structural change from the open to the closed phase was observed (Fig. S57E-F). These results indicated that the open dried phase in two smallest meso-sized crystal of 2 were too much stabilized to convert to the closed phase.

Fig. S57. Comparison of PXRD patterns before and after thermal treatment; (A) the open dried 2-meso50, (B) after heating at 200 °C of the open dried 2-meso50, (C) the open dried 2-meso300, (D) after heating at 200 °C of the open dried 2-meso300, (E) the open dried 2-meso700, (F) after heating at 200 °C of the open dried 2-meso700 (the closed 2-meso700).

65

Reversible Phase Transition between the Open Dried 2-meso700 and the Closed 2-meso700 Experimental Procedure

The open dried 2-meso700 was heated at 200 °C under vacuum condition for 1 h, and structural change to the closed 2-meso700 was confirmed by XRD measurement (Fig. S58B). After immersion to dehydrated dichloromethane solution for 10 min, a yellow green precipitate was collected by centrifugations, and dried at 70 °C under a vacuum for 1 h. Reproduction of the open dried 2-meso700 was confirmed by XRD measurement (Fig. S58C).

Fig. S58. Comparison of PXRD patterns before and after thermal treatment; (A) the open dried 2- XRPD of reversible phase change behavior of 2-meso700; (A) the open dried 2-meso700, (B) after heating at 200 °C of the open dried 2-meso700 (the closed 2-meso700), (C) dried after immersion of the closed 2-meso500 in dichloromethane (the open dried 2-meso700), (D) the closed 2-micro (XRD patterns of the closed structure), (E) simulated pattern of 2⊃ethanol (the open phase).

66

SECTION 3: Discussion About Why the Open Dried Phase Was Isolated by Crystal Downsizing of Flexible PCPs

Illustration of the Possible Energy Diagram between the Open Dried Phase and the Closed Phase

As described in the main text, the guest removal process most likely induces the formation of the open dried phase regardless of the crystal size. In the case of micrometer-sized crystals, the activation energy, ΔG‡

1, is smaller than the thermal energy (kT : k is Boltzmann’s constant). Thus the transient open dried phase easily converted to the closed phase. Because the activation energy increases due to the crystal downsizing and the atypical open dried phase can be isolated. There are two possibilities to explain this phenomenon. One is the thermodynamic reason: relative thermodynamic stability between the open dried phase and the closed phase changes with an increase of surface contribution (this eventually caused the increase of kinetic activation barrier). The other is the kinetic reason: the activation energy increases accompanied by crystal downsizing. The detail was discussed in the main text. We tend to believe that kinetic suppression best describes the process as outlined in the main text.

Fig. S59. Possible guest removal pathway and illustration of energy diagram between the open dried phase and the closed phase.

67

Comparison of Hysteretic Loop Width of Methanol Adsorption Isotherms between 1-micro and 1-meso300

In order to investigate the effect of crystal size on the kinetics of phase transition from the open dried phase to the closed phase, both phases should be isolated at least for two of samples of two distinct crystals sizes. However, we found both phases could only be isolated in one of the crystal sizes of our samples and thus it is impossible to directly evaluate kinetic contribution experimentally. On the other hand, a similar (but reverse) structural change from the closed phase to the open phase was observed during the guest accommodation process. Thus we expected that the evaluation of the crystal size effect on the kinetics of this process would enable us to indirectly estimate the kinetic hindering effect that we wanted to discuss. It has been theoretically revealed that an energy barrier between the closed phase and the open phase is the origin of the hysteretic adsorption isotherm observed in interpenetrated frameworks (21). Therefore, hysteretic widths between 1-micro and 1-meso300 were compared because they show the same structural change upon guest adsorption and desorption. As clearly shown in Fig. S60, 1-meso300 gave a wider hysteretic width than 1-micro, indicating that smaller crystals have higher kinetic hindering during the structural change process.

Fig. S60. Comparison of methanol adsorption isotherm (303 K) of the closed 1-micro (red) and the closed 1-meso300 (orange). The arrows show the hysteretic loop width of the isotherm. This indicates that smaller crystals gave wider hysteretetic loop widths.

68

Schematic Illustration of Multiple Nucleation and Growth Mechanism in Phase Transition

The flexible PCPs used in this study are categorized into martensitic materials showing a first-order phase transformation by cooperative movement of the atoms. In the extended crystals of such materials, phase transition nucleates at lattice defects, which exist even in the highest quality crystals, and propagate through the crystal as illustrated in the Fig. S61 (22, 23). Based on the assumption that larger crystals contain more nucleation sites than smaller ones, a statistical model that attributes the potency distribution of nucleation explains the enhanced kinetic suppression phase transition by crystal downsizing (24). This indicates that, even though the phase transition in meso-sized crystal is suppressed at lower temperature, this may also happen at higher temperatures due to the increase of nucleation probabilities.

Fig. S61. Schematic illustration of the difference of defect number between micrometer-sized crystal and meso-sized crystal; (A) lower temperature, and (B) higher temperature. Asterisks indicated the lattice defects as nucleation potencies.

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