Highly disordering nanoporous frameworks of lanthanide-dicarboxylates for catalysis of CO<inf>2</inf> cycloaddition with epoxides

Abstract

A series of nanoporous [LnIII4(di-nitro-BPDC)4(NO2)3(OH)(H2O)5]·n(methanol) (LnIII ​= ​PrIII, NdIII, SmIII, EuIII, GdIII, PrIII/GdIII and PrIII/EuIII; di-nitro-BPDC2- ​= ​2,2′-dinitrobiphenyl-4,4′-dicarboxylate) was synthesized and characterized. Founded on Lewis acidic LnIII possessing vacant coordination sites and functional groups of di-nitro-BPDC2-, their catalytic activities were evaluated based on the CO2 cycloaddition reactions with epoxides under ambient pressure and solvent-free conditions. Depending on catalytic conditions, satisfying turnover number and turnover frequency of 1106 and 276 h-1, respectively, could be yielded with ≥79(±4)% conversion and 87(±1)% selectivity. The correlation between the catalysis performance and structural factors is proposed on a basis of experimental and computation results. These include the restrained transportation even in the nanoporous framework and crystallographic disorder in the LnIII coordination environment. The excellent robustness of the catalysts, effects of lanthanide contraction, and synergistic activities of the heterometallic PrIII/GdIII and PrIII/EuIII catalysts are also included.