posted on 2024-01-12, 19:36authored byLiangsheng Xu, Yu Wang, Zhenkun Sun, Zheng Chen, Guofeng Zhao, Fritz E. Kühn, Wei-Guo Jia, Ruirui Yun, Rui Zhong
Single-component catalysts with integrated multiple reactive
centers
could work in concert to achieve enhanced activity tailored for specific
catalytic reactions, but they remain underdeveloped. Herein, we report
the construction of heterogeneous bimetallic porous coordination polymers
(PCPs) containing both porphyrin and N-heterocyclic
carbene (NHC) metal sites via the coordinative assembly of the NHC
functionalities. Three heterobimetallic PCPs (TIPP–Zn–Pd, TIPP–Cu–Pd and TIPP–Ni–Pd) have been prepared to verify this facile synthetic strategy for
the first time. In order to establish a cooperative action toward
the catalytic CO2 cycloaddition with epoxides, an additional
tetraalkylammonium bromide functionality has also been incorporated
into these polymeric structures through the N-substituent
of the NHC moieties. The resulting heterogeneous bimetallic catalyst TIPP–Zn–Pd exhibits the best catalytic performance
in CO2 cycloaddition with styrene oxide (SO) under solvent-free
conditions at atmospheric pressure and is applicable to a wide range
of epoxides. More importantly, TIPP–Zn–Pd works smoothly and is recyclable in the absence of a cocatalyst
under 1.0 MPa of CO2 at 60 °C. This indicates that TIPP–Zn–Pd is quite competitive with the reported
heterogeneous catalysts, which typically require a high reaction temperature
above 100 °C under cocatalyst-free conditions. Thus, this work
provides a new approach to design heterogeneous bimetallic PCP catalysts
for high-performance CO2 fixation under mild reaction conditions.