Template-free engineering of gradient pores in 2D MXene/PVDF composite membranes for high-performance solar-driven seawater desalination

Template-free blade-coating fabricates a MXene/PVDF membrane with gradient pores. • Top-small and bottom-large pores enable fast water transport and heat localization. • One-sun evaporation rate is 1.54 kg m −2  h −1 and photothermal efficiency is 93.66%. • Outstanding salt resistance and long-term durability are achieved. • Desalinated seawater meets both WHO and Chinese standards for drinking water. Addressing the global freshwater scarcity crisis, solar-driven interfacial evaporation represents a promising, energy-efficient desalination technology. Conventional porous evaporators, however, face a fundamental performance trade-off between efficient water supply and effective surface heat localization. To resolve this conflict, this study presents a novel two-dimensional (2D) MXene/polyvinylidene fluoride (PVDF) composite membrane featuring an architecturally gradient “top-small, bottom-large” pore structure, fabricated via a straightforward blade-coating and immersion precipitation phase inversion process without any template. This unique design simultaneously enables rapid capillary-driven water transport and confines thermal energy at the evaporation interface. A hydrophobic fluorinated silica (F-SiO 2 ) is further applied to ensure stable self-floating and prevent salt accumulation. The resulting membrane (~0.25 mm thick) demonstrates high porosity (~40.7%) and superior broad-spectrum light absorption (~95%). Under 1-sun illumination, it achieves a high evaporation rate of 1.54 kg m −2  h −1 and a remarkable photothermal conversion efficiency of 93.66%, while also exhibiting excellent cycling stability and salt resistance. Practical desalination tests using Bohai Sea water confirm that the purified water meets both World Health Organization (WHO) and Chinese drinking water standards. This work provides an effective strategy for designing high-performance, low-cost solar evaporator, demonstrating significant potential for scalable desalination and water purification applications. Download: Download high-res image (237KB) Download: Download full-size image