Fabrication of Nanoporous Silica Membranes by Atmospheric‐Pressure Plasma‐Enhanced Chemical Vapor Deposition Using Porogen Approach

The development of nanoporous membranes with high selectivity and stability is essential for advanced molecular separation. In this study, nanoporous silica membranes were fabricated via atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD), using hexamethyldisiloxane (HMDSO) as the precursor and methyl methacrylate (MMA) as the porogen. The hybrid composite structure was precisely controlled by adjusting deposition parameters, including deposition temperature, HMDSO concentration, and MMA/HMDSO ratio. Subsequent thermal treatment at 400°C effectively removed the porogen, yielding stable nanoporous structures with pore sizes of approximately 1 nm. Nanofiltration performance was evaluated using solutes of different molecular weights. The membranes exhibited a sharp molecular weight cutoff (∼340 g/mol), with negligible rejection of azobenzene (182 g/mol) but strong rejection (> 95%) of Basic Red 2 (351 g/mol), Brilliant Blue R (826 g/mol), and vitamin B12 (1355 g/mol). The membranes maintained stable flux values in the range of 14-15.5 kg/(m²·h), independent of solute size, indicating consistent permeability. These results demonstrate that AP-PECVD, combined with a porogen-assisted strategy, provides a versatile and scalable route for fabricating nanoporous silica membranes with excellent nanofiltration performance, highlighting strong potential for next-generation molecular separation technologies.