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.