Post-functionalization of hydroxyl-appended covalent triazine framework via borrowing hydrogen strategy for effective CO2 capture

Pore-wall function of covalent triazine frameworks (CTFs) is crucial for their applications, however, the post functionalization of CTFs for CO2 capture is scarce. Here we first obtained a hydroxyl-appended CTF by ion-othermal synthesis in molten ZnCl2. Then, the as-synthesized CTF with appended hydroxyl groups behaved as a new platform for a facile, post-synthetic functionalization by ethylenediamine (EDA) through borrowing hydrogen strategy. The intended substitution of hydroxyl groups by EDA moieties led to substantial increase in CO2 uptake (from 68 to 164 mg/g at 273 K and 1 bar) and CO2/N-2 selectivity (from 35 to 73 at 273 K), implying the favorable pore environment after post modification and the effectiveness of the introduction of CO2-philic groups to CTFs for CO2 capture. Moreover, no significant decrease in CO2 uptake was observed for the amine-functionalized CTF after five adsorption-desorption cycles, further supporting its good potential for CO2 capture.