Cobalt−Salen complexes bearing crown ether as metal-templated catalyst for cycloaddition of carbon dioxide and epoxide

Abstract

Metallosalen presents very important applications in both homogenous and heterogeneous catalysis. Correspondingly, porous polymeric metallosalen combined with the performance of organometallics and heterogeneous polymers possess potential in CO2 fixation reactions. Herein, a family collection of K@SCs were conceived and obtained by combining cobalt-salen complexes with different groups and diaminobenzene-18-crown-6 complexed with KI, which allows multiphase catalytic immobilization of CO2 to epoxides. Catalyst K@SC-3 can fix CO2 into a variety of substituted epoxides in >90% yields to the corresponding cyclic carbonates in co-catalyst-free and solvent-free conditions. Furthermore, K@SC-3 can be recovered and reused at least six times by simple centrifugal separation, demonstrating superior stability. The kinetics experiments were also carried out at varied temperatures catalyzed by K@SC-3. It is concluded that a first-order equation of epoxide was proved and the activation energy was calculated to be 27.13 KJ/mol.