Honeycomb Metal-Organic Framework with Lewis Acidic and Basic Bifunctional Sites: Selective Adsorption and CO2 Catalytic Fixation.

Abstract

Carrying out the strategy of incorporating rod secondary building units and polar functional groups in metal-organic frameworks (MOFs) to accomplish the separation of CO2 and C2 hydrocarbons over CH4 as well as CO2 fixation, an oxalamide-functionalized ligand N, N'-bis(isophthalic acid)-oxalamide (H4BDPO) has been designed. The solvothermal reaction of H4BDPO with the oxophilic alkaline-earth Ba2+ ion afforded a honeycomb Ba-MOF, {[Ba2(BDPO)(H2O)]·DMA} n (1). Due to the existence of Lewis basic oxalamide groups and unsaturated Lewis acid metal sites in the tubular channels, the activated framework presents not only high C2H6, C2H4, and CO2 uptakes and selective capture from CH4, but also efficient CO2 chemical fixation as a recyclable heterogeneous catalyst. Grand canonical Monte Carlo simulations were combined to explore the adsorption selectivities for C2H6-CH4 and C2H4-CH4 mixtures as well as the interaction mechanisms between the framework and epoxides.