Functionalized Covalent Triazine Frameworks for Effective CO₂ and SO₂ Removal

Building novel frameworks as sorbents remains a highly significant target for key environmental issues such as CO2 or SO2 emissions from coal-fired power plants. Here, we report the construction and tunable pore structure as well as gas adsorption properties of hierarchically porous covalent triazine-based frameworks (CTF-CSUs) functionalized by appended carboxylic acid/sodium carboxylate groups. The densely integrated functionalities on the pore walls bestow strong affinity to the as-made networks toward guest acid gases, in spite of their moderate Brunauer–Emmett–Teller surface areas. With abundant microporosity and integrated carboxylic acid groups, our frameworks deliver strong affinity toward CO2 with considerably high enthalpy (up to 44.6 kJ/mol) at low loadings. Moreover, the sodium carboxylate-anchored framework (termed as CTF-CSU41) shows an exceptionally high uptake of SO2 up to 6.7 mmol g–1 (42.9 wt %) even under a low SO2 partial pressure of 0.15 bar (298 K), representing the highest value for a scrubbing material reported to date. Significantly, such pore engineering could pave the way to broad applications of porous organic polymers.