Hybrid MOF-Zwitterionic Polymer Membranes for Efficient and Antifouling Solar Seawater Desalination

Abstract

Solar desalination presents a promising avenue for sustainable freshwater generation; however, fouling and long-term instability continue to pose significant challenges, particularly in complex marine environments. In this study, we introduce a solar-driven seawater evaporation membrane built on a glass fiber (GF) substrate, enhanced with a CAU-10-H metal–organic framework (MOF) layer to facilitate water transport, along with a composite photothermal top layer made of carbon black and dopamine hydrochloride (CB@DA). To tackle the fouling issue and enhance sustainability, we also grafted a zwitterionic PSBMA molecular brush onto the membrane surface, creating a hydration shield that resists biofouling and organic adhesion. Under simulated sunlight, membranes with stronger CAU-10-H binding exhibited higher evaporation efficiency. Among all tested systems, the C6-PSBMA membrane achieved the highest performance, with average evaporation rates reaching 3.73, 2.27, and 1.75 kg/m2·h on DI water, BSA-spiked saline water, and seawater, respectively. Notably, after one month of continuous exposure to seawater, PSBMA-functionalized membranes showed only a 14.26% decline in performance, compared to 24.55% in unmodified membranes, confirming their long-term antifouling effectiveness. Ion content analysis of the collected condensate met the WHO drinking water standards. These results underscore the potential of MOF-zwitterionic polymer hybrid strategies to create robust, efficient, and durable membranes for practical solar desalination applications.