Organic Solvent Nanofiltration Properties of Silica-based Membranes Derived from Propyltrimethoxysilane and Bis(triethoxysilyl)ethane

Membranes with a molecular weight cutoff of approximately 300 Da are very useful for organic solvent nanofiltration applications in the pharmaceutical industry, especially for recovery of active pharmaceutical ingredients. However, achieving such molecular weight cutoff values using polymeric membranes is challenging because most polymeric materials swell or deteriorate in organic solvents. In this study, we prepared propyl-functionalized silica (PrFS) membranes using propyltrimethoxysilane (PrTMS) and bis(triethoxysilyl)ethane (BTESE) as silica precursors. Compared with conventional templated PrFS membranes, the PrTMS–BTESE membranes exhibited higher organic solvent permeance with a high methyl orange (molecular weight: 327 Da) rejection, and did not require template removal. The membranes demonstrated excellent performance in N-methyl-2-pyrrolidone, with a permeance of up to 0.20 L m−2 h−1 bar−1 and a rejection of 89-99 % for methyl orange. Thermal treatment was critical in optimizing the membrane pore size, hydrophobicity, and separation performance. These findings highlight the potential of PrTMS–BTESE membranes for organic solvent nanofiltration. The membranes can have finely optimized properties for solvent-stable separation in pharmaceutical and chemical processes.