Competitive Binding of Ethylene, Water, and Carbon Monoxide in Metal–Organic Framework Materials with Open Cu Sites

Journal Article · 02 April 2018 · Journal of Physical Chemistry. C

DOI: https://doi.org/10.1021/acs.jpcc.8b00909 · OSTI ID:1470295

You, Wenqin ^[1]; Liu, Yang ^[1]; Howe, Joshua D.  ^[1]; Sholl, David S.  ^[1]

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1. Georgia Inst. of Technology, Atlanta, GA (United States)

Typically, metal–organic frameworks (MOFs) with open metal sites (OMS) are understood to have selectivity in olefin/paraffin separations because of π–π interactions between olefin double bonds and OMS. One concern associated with these separations is that other species that potentially bind to OMS may also be present in feed streams, causing competition for these sites. We used density functional theory (DFT) to assess the binding energy of ethylene, water, and carbon monoxide on a set of more than 60 MOFs with open Cu sites in the form of Cu dimers. A useful observation from our results is that the relative binding energies of pairs of molecules (e.g., ethylene and water) can be calculated accurately from calculations that hold the MOF structure rigid and only relax the positions of the adsorbing molecules. These kinds of calculations are far more numerically efficient than calculations that relax all degrees of freedom in the system, so this observation will be useful in future efforts to screen larger collections of materials. A second observation is that the binding energies of each molecule in the 60 MOFs are quite similar to the binding energies in CuBTC, an exemplar MOF with open Cu sites in the form of Cu dimers. Analysis of the variations that do exist in the binding energies among materials points to possible avenues for controlling either the absolute binding energies or the relative binding energies of species associated with OMS in these materials. The third observation is that two unusual MOFs can bind ethylene more strongly than water because of a dual-site binding mechanism in which an ethylene molecule can interact simultaneously with both dimers while the smaller water molecule interacts primarily with a single OMS. This observation suggests a possible avenue for developing other MOFs in which the binding energy of ethylene is higher than that of water.

• Research Organization: Georgia Inst. of Technology, Atlanta, GA (United States). Energy Frontier Research Center (EFRC) Center for Understanding and Control of Acid Gas-induced Evolution of Materials for Energy (UNCAGE-ME)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: SC0012577
• OSTI ID: 1470295
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 16 Vol. 122; ISSN 1932-7447
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY