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Title: Direct Measurement of Adsorbed Gas Redistribution in Metal–Organic Frameworks

Knowledge about the interactions between gas molecules and adsorption sites is essential to customize metal-organic frameworks (MOFs) as adsorbents. The dynamic interactions occurring during adsorption/desorption working cycles with several states are especially complicated. Even so, the gas dynamics based upon experimental observations and the distribution of guest molecules under various conditions in MOFs have not been extensively studied yet. In this work, a direct time-resolved diffraction structure envelope (TRDSE) method using sequential measurements by in situ synchrotron powder X-ray diffraction has been developed to monitor several gas dynamic processes taking place in MOFs: infusion, desorption, and gas redistribution upon temperature change. The electron density maps indicate that gas molecules prefer to redistribute over heterogeneous types of sites rather than to exclusively occupy the primary binding sites. We found that the gas molecules are entropically driven from open metal sites to larger neighboring spaces during the gas infusion period, matching the localized-to-mobile mechanism. In addition, the partitioning ratio of molecules adsorbed at each site varies with different temperatures, as opposed to an invariant distribution mode. Equally important, the gas adsorption in MOFs is intensely influenced by the gas–gas interactions, which might induce more molecules to be accommodated in an orderly compactmore » arrangement. This sequential TRDSE method is generally applicable to most crystalline adsorbents, yielding information on distribution ratios of adsorbates at each type of site.« less
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  1. Texas A & M Univ., College Station, TX (United States)
  2. Texas A & M Univ., College Station, TX (United States); Beijing Univ. of Chemical Technology (China)
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Am. Chem Soc.; Journal Volume: 137; Journal Issue: 8; 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
Research Org:
Energy Frontier Research Centers (EFRC) and Center for Gas Separations Relevant to Clean Energy Technologies (CGS), Washington, DC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
membrane, carbon capture, materials and chemistry by design, synthesis (novel materials), synthesis (self-assembly), synthesis (scalable processing)