Scalable spray-coating of covalent organic framework membranes via microdroplet confined assembly for H₂/CO₂...

The scale-up and practical implementation of covalent organic frameworks (COFs) in gas separation remains constrained by intrinsic limitations, including insolubility, infusibility and mismatched pore sizes (>0.8 nm). Drawing inspiration from air-spray principles, herein we develop a facile bottom-up spray-coating strategy for the fabrication of lasagna-like COF membranes for the first time. Theoretical calculations and detailed experiments revealed the core role of spray-coating-induced microdroplet confined assembly, wherein atomized droplets generate spatially confined environments that accelerate molecular ordering and polycondensation. Within these microdroplet-confined spaces, oligo(ethylene glycol) (OEG) side-chains suppress molecular diffusion to enhance crystallization. Such synergy enables dynamic spray cycles to drive COF growth into continuous membranes within 30 minutes. The resulting COF-OEG-4 membrane exhibits outstanding gas separation performance, with an ultrahigh H₂ permeance of 3650 GPU and an H₂/CO₂ selectivity of 41.6, ranking it among the highest-performing H₂-selective membranes. Moreover, the strategy demonstrates excellent scalability, enabling the fabrication of large-area COF composite membranes exceeding 1750 cm² directly on commercial substrates. This work critically advances both the COF processing methods and gas separation technologies.