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Title: Enhanced O-2 Selectivity versus N-2 by Partial Metal Substitution in Cu-BTC

Here, we describe the homogeneous substitution of Mn, Fe, and Co at various levels into a prototypical metal organic framework (MOP), namely Cu-BTC (HKUST-1), and the effect of that substitution on preferential gas sorption. Using a combination of density functional theory (DFT) calculations, postsynthetic metal substitutions, materials characterization, and gas sorption testing, we demonstrate that the identity of the metal ion has a quantifiable effect on their oxygen and nitrogen sorption properties at cryogenic temperatures. An excellent correlation is found between O-2/N-2 selectivities determined experimentally at 77 K and the difference in O-2 and N-2 binding energies calculated from DFT modeling data: Mn > Fe Co >> Cu. Room temperature gas sorption studies were also performed and correlated with metal substitution. The Fe-exchanged sample shows a significantly higher nitrogen isosteric heat of adsorption at temperatures close to ambient conditions (273-298 K) as compared to all other metals studied, indicative of favorable interactions between N-2 and coordinatively unsaturated Fe metal centers. Interestingly, differences in gas adsorption results at cryogenic and room temperatures are evident; they are explained by comparing experimental results with DFT binding energies (0 K) and room temperature Grand Canonical Monte Carlo simulations.
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Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 27; Journal Issue: 6
American Chemical Society (ACS)
Research Org:
Argonne National Laboratory (ANL)
Sponsoring Org:
USDOE Office of Science - Office of Basic Energy Sciences; USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States