Adsorption of environmentally significant gases (hydrogen, carbon dioxide, hydrogen sulfide, methane) in metal-organic frameworks
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Adsorption of environmentally significant gases (hydrogen, carbon dioxide, hydrogen sulfide, methane) in metal-organic frameworks
by Millward, Andrew R., Ph.D., University of Michigan, 2006, 218 pages; AAT 3208513
Advisor: Yaghi, Omar M.
School: University of Michigan
School Location: United States -- Michigan
Index terms(keywords): Hydrogen sulfide, Methane, Carbon dioxide, Adsorption, Metal-organic frameworks, Hydrogen
Source: DAI-B 67/02, Aug 2006
Source type: Dissertation
Subjects: Chemistry
Publication Number: AAT 3208513
ISBN: 9780542569593
Document URL: [url]http://proquest.umi.com/pqdweb?did=1092103131&sid=18&Fmt=2&RQT=309&VName=PQD[/url]
ProQuest document ID: 1092103131
Abstract (Document Summary)
The domain of gas adsorption science has been significantly impacted by the discovery of metal-organic frameworks (MOFs), and these materials have since matured beyond traditional characterization to veritable applications in storage and catalysis. To ascertain key structural features that lead to favorable storage capacity of H 2 , CO 2 , H 2 S and CH 4 in these materials, a subset (MOF-2, MOF-74, MOF-177, MOF-505, Cu 3 (BTC) 2 , IRMOFs-1, -3, -6, -8, -11, and -14) was examined for adsorption behavior in several temperature and pressure regimes. A study of H 2 adsorption reveals that, contrary to other microporous materials, H 2 uptake at 77 K and 760 torr among different MOFs does not scale with surface area. Materials having interpenetrated frameworks, pores of 5--10 Å diameter, or open-metal sites exhibited higher H 2 uptake, with MOF-505 adsorbing a record-breaking 2.47 wt% H 2 at 77 K and 760 torr. Low pressure, low temperature adsorption of CO 2 on several large-pore MOFs produced fully-reversible stepped isotherms with correlated step location and pore size. The initial linear region of these isotherms was identified as the Henry region, with a calculated 19(1) kJ/mol isosteric heat of adsorption for CO 2 on IRMOF-1. Subsequent low temperature in situ SXRD investigations of CO 2 adsorbed on IRMOF-1 clearly identified the primary adsorption sites found on the inorganic cluster. Toward more practical applications, nine MOFs were examined for CO 2 capacity at room temperature up to 42 bar. Capacity was found to scale roughly with surface area, and Zn 4 O(O 2 C) 6 -type frameworks produced sigmoidal isotherms, with MOF-177 adsorbing a record-breaking 147 wt% at 42 bar. Room temperature, high pressure studies of H 2 S sorption on several MOFs demonstrated capacities of 20 wt%, but the irreversible uptake was determined to be due to chemisorption rather than physisorption. Nine MOFs were examined for CH 4 capacity at room temperature up to 42 bar and revealed similar trends as the high pressure CO 2 study, with MOF-177 reversibly adsorbing 20 wt% CH 4 at room temperature and 42 bar. VERY GOOD!
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