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Title: Structural characterization of framework–gas interactions in the metal–organic framework Co 2 (dobdc) by in situ single-crystal X-ray diffraction

The crystallographic characterization of framework–guest interactions in metal–organic frameworks allows the location of guest binding sites and provides meaningful information on the nature of these interactions, enabling the correlation of structure with adsorption behavior. Here, techniques developed for in situ single-crystal X-ray diffraction experiments on porous crystals have enabled the direct observation of CO, CH 4, N 2, O 2, Ar, and P 4 adsorption in Co2(dobdc) (dobdc 4– = 2,5-dioxido-1,4-benzenedicarboxylate), a metal–organic framework bearing coordinatively unsaturated cobalt(II) sites. All these molecules exhibit such weak interactions with the high-spin cobalt(II) sites in the framework that no analogous molecular structures exist, demonstrating the utility of metal–organic frameworks as crystalline matrices for the isolation and structural determination of unstable species. Notably, the Co–CH 4 and Co–Ar interactions observed in Co 2(dobdc) represent, to the best of our knowledge, the first single-crystal structure determination of a metal–CH 4 interaction and the first crystallographically characterized metal–Ar interaction. Analysis of low-pressure gas adsorption isotherms confirms that these gases exhibit mainly physisorptive interactions with the cobalt(II) sites in Co 2(dobdc), with differential enthalpies of adsorption as weak as –17(1) kJ mol –1 (for Ar). Moreover, the structures of Co 2(dobdc)·3.8N 2, Co 2(dobdc)·5.9O 2, and Comore » 2(dobdc)·2.0Ar reveal the location of secondary (N 2, O 2, and Ar) and tertiary (O 2) binding sites in Co 2(dobdc), while high-pressure CO 2, CO, CH 4, N 2, and Ar adsorption isotherms show that these binding sites become more relevant at elevated pressures.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ; ORCiD logo [3] ; ORCiD logo [4]
  1. Univ. of California, Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ecole Polytechnique Federale de Lausanne (EPFL), Sion (Switzerland)
  4. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 8; Journal Issue: 6; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1379647