Flexible MCNTs cross-linked polyimide membranes with high light absorbance and hierarchical pore distribution for photo-thermal conversion in solar water evaporation

Solar water evaporation membranes are considered as one of the most sustainable and cost-effective strategies to realize seawater desalination, sewage treatment and distillation. However, low-cost preparation of photo-thermal conversion membranes with both high light absorbance and efficient water transport remains a longstanding challenge. Herein, versatile and simple phase inversion strategy combined with surface corrosion is applied to fabricate flexible MCNTs cross-linked polyimide membranes (MCNTs/PIMs) with hierarchical pore distribution. The surface corrosion is used to dissolve the surface dense layer formed during the phase inversion process and obtain the adjustable surface pore structure with high sunlight absorption performance. Besides, the microchannel structure is prepared to realize multiple reflection of incident light and optimize water transport by controlling the coagulating bath. The results demonstrate that the MCNTs/CPIMs exhibit high light absorption performance of 94% in the long wavelength range of 200–2500 nm. The MCNTs/CPIMs possess rapid water evaporation rate of 1.26 kg m−2 h−1 and high solar thermal conversion efficiency of 72.7%. The flexible and scalable MCNTs/CPIMs exhibit efficient light/thermal management and rapid water transport performance, which enables them promising application in sustainable, low-cost and high efficient solar water evaporation.