Functionalized UiO-66 Incorporated PVA Mixed-Matrix Membranes for Enhanced Methanol/Dimethyl Carbonate Pervaporation

Abstract

Mixed-matrix membranes were prepared for methanol (MeOH)/dimethyl carbonate (DMC) pervaporation by incorporating UiO-66-(COOH)2, UiO-66-NH2, or polyethylenimine-functionalized UiO-66-NH2 (UiO-66-N-PEI) at the same nominal loading of 2.5 wt % into sulfosuccinic acid-crosslinked poly(vinyl alcohol) (PVA). The distinctive contribution of this study is a controlled, side-by-side comparison of carboxyl-, primary-amine-, and PEI-modified UiO-66 fillers within the same polymer matrix, crosslinking formulation, fabrication procedure, and operating conditions. Characterization showed that functionalization altered not only the filler surface chemistry but also particle size and accessible porosity. UiO-66-N-PEI exhibited the lowest BET surface area and pore volume and produced a thin, continuous selective layer. At 40 °C with a feed containing 10 wt % MeOH, its incorporation decreased membrane swelling from 18.25 ± 2.04% for pristine PVA to 6.69 ± 0.90%, while increasing the MeOH/DMC sorption selectivity from 421.04 to 945.18. The UiO-66-N-PEI/PVA membrane consequently exhibited the highest separation factor of 601 while maintaining a permeation flux of 642 g·m–2·h–1. Stable performance was maintained during 7 days of operation under these conditions. When the feed MeOH concentration increased to 70 wt %, the flux increased to 1689 g·m–2·h–1, whereas the separation factor decreased to 2.67, revealing a transition toward swelling-dominated transport near the azeotropic composition. These findings show that the observed performance results from the coupled effects of PEI-associated functionality, reduced pore accessibility, altered polymer packing, and swelling resistance rather than surface wettability alone. The optimized membrane is therefore more effective for removing residual MeOH from DMC-rich streams, while additional swelling control is required for efficient near-azeotropic separation.