Desert Plant inspired Hierarchical Nanofibrous Membranes for Integrated Solar Desalination and Heavy Metal Remediation

Freshwater scarcity is a global challenge, increasingly compounded by heavy metal contamination of water systems. Solar-driven interfacial evaporation has emerged as a compelling solution owing to its energy efficiency and environmental benignity. Inspired by a desert plant - Alhagi Camelorum, we develop a biomass-based composite nanofibrous membrane to facilitate the capture of heavy metals in contaminated water and solar-driven water evaporation. Following the electrospinning of cellulose, chitosan, and an indium-based metal–organic framework (MIL-68(In)), the in-situ growth of copper oxide (CuO) nanoflowers is realized on the nanofiber network. The hierarchical porous network - assembled from interwoven nanofibers decorated with roughened nanoflowers - enables exceptional broadband light trapping. Meantime, the CuO nanoflowers serve as a catalytic interface, activating interfacial water molecules through efficient charge transfer that lowers the dissociation energy barrier, thereby enabling rapid and stable vapor generation. Under one-sun irradiation (1 kW m⁻2), the membrane achieves an evaporation rate of 2.80 kg m⁻2 h⁻1 and a photothermal conversion efficiency of 98.95%. Density functional theory calculations elucidate the atomistic and electronic mechanisms underpinning this exceptional performance. This biomass-derived photothermal membrane simultaneously combines the capture of heavy metals and water purification, representing a meaningful advance in water purification and resource recovery.