Covalent organic frameworks (COFs) with well-ordered pore structures and versatile functionalities hold tremendous promise as membrane building blocks. The facile and controllable fabrication of COF membranes remains a critical challenge. Herein, we presented a one-step vapor-liquid interfacial polymerization (VLIP) method to in-situ fabricate COF membranes on substrates under mild conditions. This VLIP method features controllable COF growth at the vapor-liquid interface, acquiring COF membranes with tunable physicochemical structure. The time-dependent amorphous-to-crystalline COF growth improved the crystallinity of COF membranes, thus improving the molecular sieving property. The increased monomer concentration endowed COF membranes with higher hydrophilicity, intensifying the water sorption ability. The resultant COF membranes conferred numerous hydrophilic pathways for water-selective transport, exhibited a high and stable n -butanol dehydration performance with permeation flux of 8160 g m −2 h −1 and separation factor of 1023 over 14 days. This VLIP method may evolve into a generic platform technique to fabricate COF membranes for efficient molecular separation.
Graphene oxide (GO) laminar membranes with fast water-transport nanochannels hold great promise for water-selective molecular separations, but the water-capture ability of membrane surfaces limits the separation performance. Herein, we engineered water-capture coatings on GO laminar membranes using structurally tunable tannic acid (TA) nanoaggregates as building blocks via a bottom-up method, acquiring heterostructured GO membranes for alcohol dehydration. The abundant oxygenated functional groups of TA coatings captured water from alcohol aqueous solutions and enhanced the surface water-capture capacity by up to 309%. We manipulated the surface water-capture ability by regulating the aggregation structure and the subsequent assembly process of the TA nanoaggregates. By virtue of the synergistic effect of the enhanced surface water-capture ability and fast water-transport GO nanochannels, the optimized heterostructured GO membrane exhibited high permeation flux of 9988 g m−2 h−1 and a superior separation factor of 4424 for n-butanol dehydration. This study provides a novel avenue to high-performance GO membranes with rationally designed heterostructures.
Covalent organic frameworks (COFs) have gained tremendous interest as membrane building blocks owing to rigid, long-range ordered and easily functionalized skeletons. The facile, controllable and task-specific construction of COF membranes lies in the frontier of membrane technology . Herein, we explored a post-synthetic linker exchange (PLE) method to engineer COF membranes for efficient alcohol dehydration. The proposed PLE method, utilizing the reversible breaking-reformation basis between pristine COF membranes and post-introduced linkers, narrowed the effective pore size to intensify molecular sieving property. Moreover, the PLE method also endowed COF membranes with more hydrophilic groups, thus improving the water sorption ability of COF membranes. The resultant COF membranes exhibited superior n -butanol dehydration performances with 3620 of selectivity, 11.35 kg m −2 h −1 of total flux and remained stable in 15-day operation. This PLE method may flourish the library of engineering COF membranes for efficient molecular separations.
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