Synergistic Water Enrichment-Evaporation in Patterned Covalent Organic Framework Janus Membranes Enables Resilient Ultrahigh-Permeance Desalination

Sustainable water management demands efficient hypersaline treatment and salt recovery. Membrane distillation (MD) is promising but limited by the trade-off between permeability and wetting resistance in conventional hydrophobic membranes. Herein, we report a patterned covalent organic framework (COF) Janus membrane with a hydrophilic-hydrophobic architecture. This membrane is fabricated via trimesoyl chloride-triggered interfacial reassembly, enabling defect-free formation of a hydrophilic terephthaldehyde-piperazine COF layer with subnanometer pores on a hydrophobic polytetrafluoroethylene (PTFE) substrate. This structure leverages a synergistic "water enrichment-evaporation" mechanism, where confined pores and the patterned hydrophilic surface reorganize the hydrogen-bond network of water, dramatically accelerating transport and evaporation. The COF Janus membrane achieves >99.99% NaCl rejection and an ultrahigh water flux of 121.7 L m-2 h-1, a 72% improvement over the PTFE membrane. It also exhibits robust resistance to surfactant-induced wetting and oil fouling, ensuring long-term stability under harsh conditions. This work resolves the permeability-wetting trade-off in MD and establishes a versatile platform for next-generation high-performance desalination membranes.