Rational design of catalyst with complementary functionality and swing-like architecture for efficient CO₂ cycloaddition

In this work, a series of multifunctional integrated heterogeneous catalysts (PS-[EIMBr-COO] 2 M, M = Fe 2+ , Co 2+ , Ni 2+ and Zn 2+ ) with abundant active sites and a dynamic swing-active architecture were successfully constructed, which were applied in catalytic cycloaddition of CO 2 and propylene oxide (PO) for efficient propylene carbonate (PC) preparation. The PS-[EIMBr-COO] 2 Co catalyst demonstrated the best catalytic activity with a 98.92 % conversion of PO, a 99.00 % selectivity towards PC, and a TOF value of 120.75 h −1 at 110 °C. The characterization techniques and theoretical simulation revealed that the excellent catalytic performance of the PS-[EIMBr-COO] 2 Co catalyst was attributed to the synergistic effect of the Lewis acid center, imidazolinium groups (Lewis base), Br − ions (nucleophilic site), and swing-active structure. The synergistic effect between active sites reduced the reaction energy barrier of the rate-determining step, and the swing-active structure in catalyst was believed to improve the contact efficiency between the active site and the reaction substrate. The synthesized PS-[EIMBr-COO] 2 Co catalyst was structurally stable and maintained its initial catalytic ability after seven cycles. Moreover, the PS-[EIMBr-COO] 2 Co catalyst shows good substrate universality for the cycloaddition reactions of epoxides. The catalyst construction strategy of functional integration and flexible active structure has high universality for cycloaddition catalyst design, and has important guiding significance for rational design of efficient heterogeneous catalysts.