Elucidating the role of g-C₃N₄ nanostructural dimensionality in organosilica composite membranes for optimized molecular separation through pervaporation

1,2-bis(triethoxysilyl)ethane (BTESE)-derived organosilica membranes have good acid-resistant stability in the application of acetic acid dehydration via pervaporation technology. To enhance the separation performance of water (0.26   nm) and acetic acid (0.43   nm), graphitic carbon nitride (g-C 3 N 4 ) distinguished by its periodic nanoporosity (0.31-0.34   nm) and hydrophilic functionality, offers exceptional potential for organosilica-based membranes improvement. Herein, we tailored g-C 3 N 4 nanostructures as 2D nanosheets (4   nm thickness) and 0D quantum dots (4   nm diameter), and embedded them into BTESE membranes. For their thermal stability, the nanosheets enhanced structural integrity due to interlayer covalent/hydrogen bonding networks, while quantum dots exhibited a larger weight loss but preserved more residues at 800   o C. Nanosheets incorporated BTESE/g-C 3 N 4 composites reduced BTESE pore size, amplified surface hydrophilicity and membrane thickness, whereas quantum dots with abundant functional groups minimally altered BTESE matrix structures. In pervaporation of acetic acid/water, BTESE performance was improved by both morphologies of g-C 3 N 4 fillers at the same optimal loading. The nanosheet-incorporated membrane (BTESE/CN-NSs-3) achieved a separation factor of 2327 with a flux of 2.35   kg/m 2 ·h, while quantum dots-incorporated membrane (BTESE/CN-QDs-3) exhibited a higher flux of 2.52   kg/m 2 ·h but a lower separation factor of 1352. In feed concentration (50–90   wt% AcOH) and temperature dependent (55–95 °C) operations, nanosheets facilitated molecule sieving through interlayer channels, whereas quantum dots enabled lower-resistance pathways by diffusivity dominated permeation. This work establishes g-C 3 N 4 dimensionality modulating organosilica membrane’s transport hierarchy, providing a selection for developing acid-resistant membranes in improving flux and separation factor.