Enhancing dehydration performance of isopropanol for flexible hybrid silica composite membranes with spray-coated active layer on polymers

Organically bridged silica has been proven to be promising precursors for fabricating silica-based organic–inorganic hybrid membranes with excellent permselectivity. However, the large-area deposition of defect-free hybrid silica membranes onto the polymer substrate has always been an enormous challenge. Herein, we reported a fast and facile approach for the large-area production of flexible silica-based hybrid membranes, where a thin and uniform ethylene-bridged silica active layer was coated on a microporous polymer substrate via a spray coating process with a single-pass method. First, the optimal deposition conditions were investigated and established, including sol concentrations and different solvent systems that are used to prepare hybrid silica sol, as well as various spray coating conditions. Subsequently, thus-produced flexible hybrid silica composite membranes exhibited superior isopropanol (IPA) dehydration performance by vapor permeation for a 90 wt% isopropanol aqueous solution, with water permeation flux reaching 4.0 kg m-2h−1 and with H2O/IPA separation factor exceeding 1000 (the selectivity of H2O/IPA is 770). This work has shown that the single-pass spray coating is a useful strategy for the large-scale fabrication of the flexible hybrid silica composite membrane.