Air Separation by Catechol-Ligated Transition Metals: A Quantum Chemical Screening

The separation of O2 and N2 from air is of great importance in a variety of industrial contexts, but the primary means of accomplishing the separation is cryogenic distillation, an energy-intensive process. A material that could enable air separation to occur at conventional temperatures would be of great economic and environmental benefit. Metalated catecholates within metal–organic frameworks have been considered for other gas separations and are shown here to have significant potential for air separation. Calculations of interaction energies between catecholates with first-row transition metals and guests O2 and N2 were performed using density functional theory and multireference complete active space self-consistent field followed by second-order perturbation theory. A general recipe is offered for active space selection for metalated catecholate systems. The multireference results are used to rationalize O2 binding in terms of redox activity with the metalated catecholate. O2 is predicted to bind mor...