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Metal-organic frameworks (MOFs) have received a great deal of attention for their potential in atmospheric filtering, and recent work has shown that catecholate linkers can bind metals, creating MOFs with monocatecholate metal centers and abundant open coordination sites. In this study, M-catecholate systems (with M = Mg2+, Sc2+, Ti2+, V2+, Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) were used as computational models of metalated catecholate linkers in MOFs. Nitric oxide (NO) is a radical molecule that is considered an environmental pollutant and is toxic if inhaled in large quantities. Binding NO is of interest in creating atmospheric filters, at both the industrial and personal scale. The binding energies of NO to the metal-catecholate systems were calculated using density functional theory (DFT) and complete active space self-consistent field (CASSCF) followed by second-order perturbation theory (CASPT2). Selectivity was studied by calculating the binding energies of additional guests (CO, NH3, H2O, N2, and CO2). The toxic guests have stronger binding than the benign guests for all metals studied, and NO has significantly stronger binding than other guests for most of the metals studied, suggesting that metal-catecholates are worthy of further study for NO filtration. Certain metal-catecholates also show potential for separation of N2 and CO2 via N2 activation, which could be relevant for carbon capture or ammonia synthesis.
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The authors thank Dale Pahls for useful discussions and Gary Bondarevsky for insight into preliminary exploration. The authors also acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources that contributed to the research results reported within this paper. This research is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, under Award DE-FG02-12ER16362.
© 2017 American Chemical Society.