Janus Vapor‐Gap Membrane Coupling Superhydrophobic Evaporation and Superhydrophilic Condensation for Pressure‐Driven Desalination

Pressure‐driven distillation (PD) has emerged as a transformative technology for harnessing non‐conventional water resources, leveraging hydraulic pressure to accelerate vapor generation and transport across vapor‐gap membranes. Despite its promise, the paradigm of conventional PD is fundamentally constrained by overlooked thermodynamic energy barrier, which severely limits overall process efficiency. Herein, we report the first conceptualization and fabrication of an ultra‐selective Janus vapor‐gap membrane engineered explicitly for PD, featuring a superhydrophilic, highly crystalline, and defect‐free covalent organic framework (COF) layer that decisively overcomes this limitation. The Janus membrane embodies a bilayered architecture with the upper layer functions as a vapor generation zone, sustaining a robust gas‐liquid interface for efficient evaporation, while the lower layer serves as a confined condensation zone that significantly reduces the energy barrier for vapor‐to‐liquid phase transition. This strategic spatial decoupling of evaporation and condensation enables a synergistic enhancement of the entire PD process. The resulting Janus membrane achieves near‐complete rejections of nonvolatile solutes. In practical desalination scenarios, it demonstrates outstanding anti‐fouling and chlorine resistance. This work not only highlights the potential of crystalline porous materials in PD technology, but also provides a pathway for architected Janus membranes that transcend the efficiency limits of conventional desalination processes.