Charge-Separated and Lewis Paired Metal-Organic Framework for Anion Exchange and CO2Chemical Fixation

Charge-separated metal-organic frameworks (MOFs) are a unique class of MOFs that can possess added properties originating from the exposed ionic species. A new charge-separated MOF, namely, UNM-6 synthesized from a tetrahedral borate ligand and Co(2+)cation is reported herein. UNM-6 crystalizes into the highly symmetricP43nspace group with fourfold interpenetration, despite the stoichiometric imbalance between the B and Co atoms, which also leads to loosely bound NO(3)(-)anions within the crystal structure. These NO(3)(-)ions can be quantitatively exchanged with various other anions, leading to Lewis acid (Co2+) and Lewis base (anions) pairs within the pores and potentially cooperative catalytic activities. For example, UNM-6-Br, the MOF after anion exchange with Br(-)anions, displays high catalytic activity and stability in reactions of CO(2)chemical fixation into cyclic carbonates.