Post-modified porphyrin imine gels with improved chemical stability and efficient heterogeneous activity in CO2 transformation

Abstract

Efficient heterogeneous gel catalysts have been developed based on dynamic covalent chemistry and post-modification methods for the chemical fixation of CO₂. Various porphyrin-based imine gels are synthesized and subsequent reduction of imine bonds and metallation with various metal centers yields gel catalysts. The gels are characterized by a number of techniques including SEM, TEM, EDX, FT-IR, CP/MAS ¹³C NMR, and XPS. The resulting gels not only have network structures including micro-, meso- and macropores, but also show improved chemical stability and strong interactions between CO₂ and pore channels. The gel catalysts show good catalytic activity towards the cycloaddition of epoxides with CO₂ to cyclic carbonates using wet gels. Post-modified gel catalysts with a Zn(II) center (ZnTAPP-Go-r) show a high product yield and high stability with recyclability over 5 cycles.