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Title: Molecular Retrofitting Adapts a Metal–Organic Framework to Extreme Pressure

Authors:
ORCiD logo [1];  [1];  [2]; ORCiD logo [3]
  1. Department of Chemistry, University of California−Berkeley, Berkeley, California 94720, United States; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States; Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720, United States; Berkeley Global Science Institute, Berkeley, California 94720, United States
  2. King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
  3. Department of Chemistry, University of California−Berkeley, Berkeley, California 94720, United States; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States; Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720, United States; Berkeley Global Science Institute, Berkeley, California 94720, United States; King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Gas Separations Relevant to Clean Energy Technologies (CGS)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1389025
DOE Contract Number:
SC0001015
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Central Science; Journal Volume: 3; Journal Issue: 6; Related Information: CGS partners with University of California, Berkeley; University of California, Davis; Lawrence Berkeley National Laboratory; University of Minnesota; National Energy Technology Laboratory; Texas A&M University
Country of Publication:
United States
Language:
English
Subject:
membrane, carbon capture, materials and chemistry by design, synthesis (novel materials), synthesis (self-assembly), synthesis (scalable processing)

Citation Formats

Kapustin, Eugene A., Lee, Seungkyu, Alshammari, Ahmad S., and Yaghi, Omar M. Molecular Retrofitting Adapts a Metal–Organic Framework to Extreme Pressure. United States: N. p., 2017. Web. doi:10.1021/acscentsci.7b00169.
Kapustin, Eugene A., Lee, Seungkyu, Alshammari, Ahmad S., & Yaghi, Omar M. Molecular Retrofitting Adapts a Metal–Organic Framework to Extreme Pressure. United States. doi:10.1021/acscentsci.7b00169.
Kapustin, Eugene A., Lee, Seungkyu, Alshammari, Ahmad S., and Yaghi, Omar M. Tue . "Molecular Retrofitting Adapts a Metal–Organic Framework to Extreme Pressure". United States. doi:10.1021/acscentsci.7b00169.
@article{osti_1389025,
title = {Molecular Retrofitting Adapts a Metal–Organic Framework to Extreme Pressure},
author = {Kapustin, Eugene A. and Lee, Seungkyu and Alshammari, Ahmad S. and Yaghi, Omar M.},
abstractNote = {},
doi = {10.1021/acscentsci.7b00169},
journal = {ACS Central Science},
number = 6,
volume = 3,
place = {United States},
year = {Tue Jun 06 00:00:00 EDT 2017},
month = {Tue Jun 06 00:00:00 EDT 2017}
}
  • Despite numerous studies on chemical and thermal stability of metal-organic frameworks (MOFs), mechanical stability remains largely undeveloped. No strategy exists to control the mechanical deformation of MOFs under ultrahigh pressure, to date. We show that the mechanically unstable MOF-520 can be retrofitted by precise placement of a rigid 4,4'-biphenyldicarboxylate (BPDC) linker as a "girder" to afford a mechanically robust framework: MOF-520-BPDC. This retrofitting alters how the structure deforms under ultrahigh pressure and thus leads to a drastic enhancement of its mechanical robustness. While in the parent MOF-520 the pressure transmitting medium molecules diffuse into the pore and expand the structuremore » from the inside upon compression, the girder in the new retrofitted MOF-520-BPDC prevents the framework from expansion by linking two adjacent secondary building units together. As a result, the modified MOF is stable under hydrostatic compression in a diamond-anvil cell up to 5.5 gigapascal. The increased mechanical stability of MOF-520-BPDC prohibits the typical amorphization observed for MOFs in this pressure range. Direct correlation between the orientation of these girders within the framework and its linear strain was estimated, providing new insights for the design of MOFs with optimized mechanical properties.« less
  • A rational strategy has been used to immobilize open metal sites in ultramicroporosity for stronger binding of multiple H{sub 2} molecules per unsaturated metal site for H{sub 2} storage applications. The synthesis and structure of a mixed zinc/copper metal/organic framework material Zn{sub 3}(BDC){sub 3}[Cu(Pyen)] {center_dot} (DMF){sub 5}(H{sub 2}O){sub 5} (H{sub 2}BDC = 1,4 benzenedicarboxylic acid and PyenH{sub 2} = 5-methyl-4-oxo-1,4-dihydro-pyridine-3-carbaldehyde) is reported. Desolvation provides a bimodal porous structure Zn{sub 3}(BDC){sub 3}[Cu(Pyen)] (M{prime}MOF 1) with narrow porosity (<0.56 nm) and an array of pores in the bc crystallographic plane where the adsorbate-adsorbent interactions are maximized by both the presence of openmore » copper centers and overlap of the potential energy fields from pore walls. The H{sub 2} and D{sub 2} adsorption isotherms for M{prime}MOF 1 at 77.3 and 87.3 K were reversible with virtually no hysteresis. Methods for determination of the isosteric enthalpies of H{sub 2} and D{sub 2} adsorption were compared. A virial model gave the best agreement (average deviation <1 standard deviation) with the isotherm data. This was used in conjunction with the van't Hoff isochore giving isosteric enthalpies at zero surface coverage of 12.29 {+-} 0.53 and 12.44{+-} 0.50 kJ mol{sup -1} for H{sub 2} and D{sub 2} adsorption, respectively. This is the highest value so far observed for hydrogen adsorption on a porous material. The enthalpy of adsorption, decreases with increasing amount adsorbed to 9.5 kJ mol{sup -1} at {approx} 1.9 mmol g{sup -1} (2 H{sub 2} or D{sub 2} molecules per Cu corresponding to adsorption on both sides of planar Cu open centers) and is virtually unchanged in the range 1.9-3.6 mmol g{sup -1}. Virial analysis of isotherms at 87.3 K is also consistent with two H{sub 2} or D{sub 2} molecules being bound to each open Cu center. The adsorption kinetics follow a double exponential model, corresponding to diffusion along two types of pores, a slow component with high activation energy (13.35 {+-} 0.59 kJ mol{sup -1}) for the narrow pores and a faster component with low activation energy (8.56 0.41 kJ mol{sup -1}). The D{sub 2} adsorption kinetic constants for both components were significantly faster than the corresponding H{sub 2} kinetics for specific pressure increments and had slightly lower activation energies than the corresponding values for H{sub 2} adsorption. The kD{sub 2}/kH{sub 2} ratio for the slow component was 1.62 {+-} 0.07, while the fast component was 1.38 {+-} 0.04 at 77.3 K, and the corresponding ratios were smaller at 87.3 K. These observations of kinetic isotope quantum molecular sieving in porous materials are due to the larger zero-point energy for the lighter H{sub 2}, resulting in slower adsorption kinetics compared with the heavier D{sub 2}. The results show that a combination of open metal centers and confinement in ultramicroporosity leads to a high enthalpy for H{sub 2} adsorption over a wide range of surface coverage and quantum effects influence diffusion of H{sub 2} and D{sub 2} in pores in M{prime}MOF 1.« less
  • The adsorption and diffusivity of methane, ethane, n-butane, n-hexane and cyclohexane in a metal organic framework (MOF) with the organic linker tetrakis[4-(carboxyphenyl)oxamethyl]methane, the metal salt, Zn2+, and organic pillar, 4,4’-bipyridin was studied using molecular dynamics simulations. For the n-alkanes, the longer the chain, the lower the free energy of adsorption, which was attributed to a greater number of contacts between the alkane and MOF. Cyclohexane had a slightly higher adsorption free energy than n-hexane. Furthermore, for cyclo- and n-hexane, there were no significant differences in adsorption free energies between systems with low to moderate loadings. The diffusivity of the n-alkanesmore » was found to strongly depend on chain length with slower diffusion for longer chains. Cyclohexane had no effective diffusion, suggesting that the selectivity the MOF has towards n-hexane over cyclohexane is the result of kinetics instead of energetics. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.« less
  • A rational strategy has been used to immobilize open metal sites in ultramicroporosity for stronger binding of multiple H2 molecules per unsaturated metal site for H2 storage applications. The synthesis and structure of a mixed zinc/copper metal-organic framework material Zn3(BDC)3[Cu(Pyen)] (DMF)5(H2O)5 (H2BDC ) 1,4 benzenedicarboxylic acid and PyenH2 ) 5-methyl-4-oxo-1,4-dihydro-pyridine-3-carbaldehyde) is reported. Desolvation provides a bimodal porous structure Zn3(BDC)3[Cu(Pyen)] (M MOF 1) with narrow porosity (<0.56 nm) and an array of pores in the bc crystallographic plane where the adsorbate adsorbent interactions are maximized by both the presence of open copper centers and overlap of the potential energy fields frommore » pore walls. The H2 and D2 adsorption isotherms for M MOF 1 at 77.3 and 87.3 K were reversible with virtually no hysteresis. Methods for determination of the isosteric enthalpies of H2 and D2 adsorption were compared. A virial model gave the best agreement (average deviation <1 standard deviation) with the isotherm data. This was used in conjunction with the van t Hoff isochore giving isosteric enthalpies at zero surface coverage of 12.29 ( 0.53 and 12.44 ( 0.50 kJ mol-1 for H2 and D2 adsorption, respectively. This is the highest value so far observed for hydrogen adsorption on a porous material. The enthalpy of adsorption, decreases with increasing amount adsorbed to 9.5 kJ mol-1 at 1.9 mmol g-1 (2 H2 or D2 molecules per Cu corresponding to adsorption on both sides of planar Cu open centers) and is virtually unchanged in the range 1.9-3.6 mmol g-1. Virial analysis of isotherms at 87.3 K is also consistent with two H2 or D2 molecules being bound to each open Cu center. The adsorption kinetics follow a double exponential model, corresponding to diffusion along two types of pores, a slow component with high activation energy (13.35 ( 0.59 kJ mol-1) for the narrow pores and a faster component with low activation energy (8.56 ( 0.41 kJ mol-1). The D2 adsorption kinetic constants for both components were significantly faster than the corresponding H2 kinetics for specific pressure increments and had slightly lower activation energies than the corresponding values for H2 adsorption. The kD2/kH2 ratio for the slow component was 1.62 ( 0.07, while the fast component was 1.38 ( 0.04 at 77.3 K, and the corresponding ratios were smaller at 87.3 K. These observations of kinetic isotope quantum molecular sieving in porous materials are due to the larger zero-point energy for the lighter H2, resulting in slower adsorption kinetics compared with the heavier D2. The results show that a combination of open metal centers and confinement in ultramicroporosity leads to a high enthalpy for H2 adsorption over a wide range of surface coverage and quantum effects influence diffusion of H2 and D2 in pores in M MOF 1.« less
  • A newly designed octatopic carboxylate ligand, tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane (TDM 8–) has been used to connect a dicopper paddlewheel building unit affording a metal–organic framework (MOF), Cu₄(H₂O)₄(TDM)·xS (PCN-26·xS, S represents noncoordinated solvent molecules, PCN = porous coordination network) with novel structure, high gas uptake, and interesting gas adsorption selectivity. PCN-26 contains two different types of cages, octahedral and cuboctahedral, to form a polyhedron-stacked three-dimensional framework with open channels in three orthogonal directions. Gas adsorption studies of N₂, Ar, and H₂ on an activated PCN-26 at 77 K, 1 bar, reveals a Langmuir surface area of 2545 m²/g, a Brunauer–Emmett–Teller (BET) surface areamore » of 1854 m²/g, a total pore volume of 0.84 cm³/g, and a H₂ uptake capacity of 2.57 wt %. Additionally, PCN-26 exhibits a CO₂/N₂ selectivity of 49:1 and CO₂/CH₄ selectivity of 8.4:1 at 273 K. To investigate properties of gas adsorption and the adsorption sites for CO₂ in activated PCN-26, theoretical simulations of the adsorption isotherms of CO₂, CH₄, and N₂ at different temperatures were carried out. Experimental results corroborate very well with those of molecular simulations.« less