Multifunctional ionic covalent triazine framework as heterogeneous catalysts for efficient CO2 cycloaddition

Abstract

The abundant triazine rings with the good affinity for CO₂ molecules in covalent triazine frameworks (CTFs) can capture and activate CO₂ molecules, making CTFs a potential candidate for CO₂ cycloaddition reaction. However, due to the single active site, the realization of high catalytic performance commonly requires the assistance of cocatalysts or harsh reaction conditions. In this study, several novel ionic covalent triazine frameworks (MCTFs, BCTFs and YCTFs) multifunctional heterogeneous catalysts were synthesized for CO₂ cycloaddition reactions. The prepared CTFs catalysts have outstanding pore structure and uniformly distributed active sites (N Lewis basic sites in triazine ring and Cl^– nucleophilic sites). The optimal catalyst MCTF-10 has good CO₂ enrichment capacity and high adsorption selectivity. In addition, the catalyst shows an outstanding catalytic performance for the coupling reaction of CO₂ and propylene oxide, with 96 % of yield and 99 % of selectivity for the product under metal-, solvent- and cocatalyst-free parameters (110 °C, initial CO₂ pressure 1 MPa, 4 h). Even under diluted CO₂ concentration (15 % CO₂, 85 % N₂) and mild conditions (80 °C, 0.1 MPa, 24 h), the synthetized CTFs exhibits an outstanding catalytic activity. The excellent catalytic performance, along with the good cycling stability and broad applicability of epoxides, make it a competitive catalyst for catalyzing the CO₂ cycloaddition reaction.