In situ carboxyl functionalization of hybrid organosilica reverse osmosis membranes for water desalination

A new strategy is proposed to tune the surface and structural properties of hybrid organosilica membranes. It involves an in situ carboxyl functionalization via the thiol-ene click reaction between the double bonds of bis(triethoxysilyl)ethylene and mercaptosuccinic acid. Water sorption measurements and quantum chemical calculations confirm that the introduction of carboxyl functionalities into the organosilica networks leads to a compact pore structure and an improved affinity for water molecules. Compared to the original ethenylene-bridged organosilica membranes, the in situ carboxyl functionalization doubles the membrane permeability without any drop in water/salt selectivity in reverse osmosis (RO). Furthermore, the carboxyl functionalized organosilica membrane demonstrates high durability during a continuous RO desalination process of 200 h, showing excellent prospects as a high efficiency and robust molecular separation membrane for environmental and industrial applications. Carboxyl functionalization of organosilica networks is realized by an in situ thiol-ene click reaction, leading to a simultaneous improvement in membrane permeability and selectivity.