Design and synthesis of novel pyridine-rich cationic covalent triazine framework for CO2 capture and conversion

The covalent triazine frameworks (CTFs) have great application prospects in gas adsorption and separation, pollutant adsorption and heterogeneous catalysis due to their high specific surface area, rich nitrogen content and high physicochemical stability. Moreover, the simultaneous introduction of Lewis acid active sites (cation part) and Lewis base active sites (halogen anion) into the structure of CTFs will not only increase the adsorption capacity of CO2, but also greatly improve the catalytic performance of the CO2 cycloaddition reaction. Herein, two novel cationic CTFs (CCTFs) based on 1,3,5-Tris(4-cyanopyridinium-1-ylmethyl)-benzene tribromide (TPM) were successfully synthesized by using anhydrous ZnCl2 as a catalyst and reaction medium to force the cyanide group into trimerization. The obtained CTF-TPMs with ample pyridine cationic sites have outstanding chemical and thermal stability even in strong acid and strong base solutions, high specific surface area (up to 1206 m2 g−1) and high CO2 adsorption capacity (up to 61.4 cc g−1, at 1 bar and 273 K). In addition, in the absence of co-catalyst and noble metal, CTF-TPMs can synergistically catalyze the cycloaddition of CO2 with epoxy compounds to form corresponding cyclic carbonates with the synergy effect of the pyridinium salts and halide ions. More importantly, the catalytic performance of CTF-TPMs and their structural framework basically remain unchanged after 5 times recycles, which makes them excellent practical application prospect.