Degradable and Recyclable Solar Desalination Membranes Based on Naturally Occurring Building Blocks

Solar steam generation is a robust and environmentally friendly way to obtain fresh water and alleviate the water shortage problem. Although a wide variety of steam generation devices have been well documented, most fabricated materials are often only suitable for one device and generally difficult to be removed, resulting in a disposable device. This may raise serious concerns about the total cost issues, particularly for those devices with complex and well-tailored microstructures. Thus, it is urgent to develop a robust and dynamic photothermal coating that can be easily removed and flexibly switched between different installations with stable photothermal conversion ability. In this work, we report a degradable and recyclable metal-phenolic network-based photothermal coating assembled from two kinds of naturally occurring building blocks [gallic acid (GA) and Fe(III)]. Hydrophilic poly(vinylidene fluoride) (PVDF) was selected as the substrate, resulting in the robust GA@Fe(III)@PVDF membrane, which can achieve a high evaporation rate of 1.539 kg m–2 h–1 and a superb steam generation efficiency of 90.2% under 1 sun illumination. Impressively, the GA@Fe(III) coating can be degraded under acidic condition rapidly, and the recovered PVDF can be recoated by the GA@Fe(III) networks again. The steam generation performance of the recovered GA@Fe(III)@PVDF can remain stable over 150 degrading and recoating cycles. We believed that this work could offer opportunities to fabricate low-cost, sustainable, and degradable photothermal coatings for solar steam generation.