Ultrathin covalent organic framework film as membrane gutter layer for high-permeance CO2 capture

Thin film composite membranes (TFCMs) have displayed attractive CO2 capture performance, in which a critical gutter layer with small transport resistance is needed to prevent the penetration of the top separation layer into the bottom porous support for realizing high CO2 permeance. However, traditional and recently developed gutter layer materials face some issues such as physical aging, thickness-dependent permeability, instability, or poor compatibility. Herein, wholly organic, orientated, two-dimensional covalent organic framework (COF) films, for the first time, are used as the novel gutter layers due to the ideal pore size, intrinsic porosity, small transport resistance, good compatibility with polymer matrix, good anti-aging capability and high stability. Commercial or photo-initiated crosslinked polymer can be deposited compatiblely on the COF gutter layer with a thickness as thin as 55 nm, an ultrathin thickness that traditional gutter layers are challenging to attain. As a result, one optimized TFCM realizes high CO2 capture performance with CO2 permeance of 1843 gas permeation units (GPU) and CO2/N2 separation selectivity of 28.2, which displays unique advantages over other gutter layer-based TFCMs and meets the performance target for CO2 capture (CO2 permeance > 1000 GPU, CO2/N2 selectivity > 20).