Flexible, scalable, and bifunctional MOF-based nanofibrous membranes with gems-on-string structure for simultaneous efficient water evaporation and pollution remediation

Solar-driven interfacial evaporation offers a viable pathway for alleviating global water shortages. However, a significant challenge arises when the source water contains organic contaminants, as the evaporation process can lead to the enrichment and exacerbation of pollution in the remaining water. Herein, we constructed a flexible bifunctional nanofibrous membrane evaporator featuring a gems-on-string structure, designed to concurrently realize clean water production and source water purification. This was achieved through the uniform decoration of polypyrrole (PPy) nanoparticles onto silica nanofibers, followed by the tactful immobilization of zeolitic imidazolate framework (ZIF-67) polyhedrons on the fibers via a facile hot-pressing approach. The micro-nano hierarchical structure of the gems-on-string fibers enables multiple reflections between adjacent gems, significantly enhancing full-spectrum light absorption (96.3 %) and photothermal conversion. Moreover, the superhydrophilic and hierarchically interconnected channels within the membrane facilitate water transport and evaporation enthalpy diminution. Furthermore, the synergistic effects of localized heat from PPy, and photocatalysis and cobalt sites from ZIF-67 significantly promote the activation of peroxymonosulfate. As a result, the bifunctional evaporator achieves a rapid evaporation rate (2.29 kg m -2 h −1 ) with a remarkable solar-water conversion efficiency (93.2 %) under one sun, outperforming most state-of-art evaporators, while maintaining superior oxytetracycline removal (92.5 %). Significantly, the evaporator delivers a daily freshwater output (5.3 kg m −2 ) when treating complex wastewater/seawater. This study not only presents an efficient strategy for fabricating flexible high-performance photothermal-catalytic membranes, but also provides a sustainable platform for freshwater production and sewage purification.