1,2-bis(triethoxysilyl)methane (BTESM)-derived organic–inorganic membranes with controlled sol particle size: Preparation and pervaporation dehydration performance of isopropanol aqueous solutions

1,2-bis(triethoxysilyl)methane (BTESM) is a bridged-type organoalkoxysilane, which was utilized for organic–inorganic membranes preparation via a sol–gel method to achieve high permselectivity, thus are promising for dehydration and purification of organic solvents. However, the particle size of the derived sol is crucial for membrane preparation during sol–gel processing, significantly influencing the membrane’s performance. Herein, we reported a novel strategy of controlling the sol particle size by adjusting the pH during the preparation process. BTESM-derived membranes were prepared by BTESM-H + sol and BTESM-swing sol, which were subsequently employed for the dehydration of isopropanol (IPA) through pervaporation (PV). Compared with the BTESM-H + sol, the particle size of the BTESM-swing sol prepared by the pH-swing method was increased from 1.3 nm to 32.7 nm. The larger particle size could hinder the permeation into the intermediate layer. Meanwhile, the dense arrangement of silica particles could efficiently retain IPA molecules, thereby substantially enhancing the rejection rate of IPA. The average particle size of the BTESM-swing sol was 18.7 nm at an acid-base ratio of 1.2 and acid-silicon ratio of 0.55, resulting a permeate flux of 1.04 kg·m −2 ·h −1 and separation factor of 521, while IPA rejection rate was 97.84 %. This work has shown that adjusting the pH during the process is a useful strategy of controlling the sol size for the preparation of organic–inorganic membranes. Hence, the control of sol particle size to achieve a high-performing membrane layer offers a novel approach to producing diverse membrane materials.