Amine-Functionalized Covalent Organic Framework for Direct Air Capture of Carbon Dioxide

Covalent organic frameworks (COFs) are promising materials for CO 2 capture due to their tunable porosity and chemical versatility. Herein, we report the postsynthetic functionalization of vinylene-linked V-COF-1 with tris(2-aminoethyl)amine (TAEA), yielding an amine-appended framework (V-COF-tris) with enhanced CO 2 affinity. Although amine incorporation reduces the surface area, it introduces abundant chemisorption sites that significantly improve CO 2 adsorption performance. V-COF-tris exhibits CO 2 uptakes of 1.80 and 2.68 mmol·g –1 at 100 kPa and 298 and 273 K, respectively, together with a high isosteric heat of adsorption ( Q st = 59 kJ·mol –1 ), indicating a stronger CO 2 affinity than the physisorption-dominated V-COF-1 ( Q st = 23 kJ·mol –1 ). The functionalized material also demonstrates markedly enhanced CO 2 selectivity, as confirmed by Ideal Adsorbed Solution Theory (IAST) calculations for CO 2 /N 2 mixtures under both dilute (400 ppm) and concentrated conditions. Dynamic breakthrough experiments further validate the improved performance of V-COF-tris under simulated direct air capture conditions, showing prolonged CO 2 retention and stable cyclic operation. Overall, this work demonstrates that postsynthetic amine functionalization effectively transforms COFs into chemisorption-driven sorbents with enhanced CO 2 affinity, providing a promising strategy for low-pressure carbon capture applications.