Hydroxyl-Functionalized Ultrathin Covalent Organic Framework Membrane for Fast H2/CO2 Separation

Utilization of covalent organic frameworks (COFs) as membrane materials presents a promising approach to addressing the permeation-selection trade-off problem. However, the pore dimensions of COF membranes are considerably larger than those of CO 2 molecules, which constrains the efficacy in H 2 /CO 2 separation. This study presents a novel strategy for H 2 /CO 2 separation by modifying the pore walls of a COF membrane. DHTA-Hz, which contains hydroxyl (−OH) functional groups, selectively adsorbs CO 2, confining it within the channels while permitting H 2 to permeate with minimal resistance. Despite having a pore size of 0.84 nm, the membrane exhibits a remarkable H 2 /CO 2 selectivity of 10.8 and outstanding H 2 permeability of 1921 GPU. The overall performance exceeds the Robeson upper bound, highlighting the potential for efficient gas separation. Theoretical simulations validate the effectiveness of this pore-wall adsorption strategy, offering innovative insights into the design of COF membranes for enhanced gas separation.