Covalent Organic Framework with Tailored Angstrom-Scale Motifs for Efficient Water Activation and Desalination.

Interfacial evaporation is recognized as a promising sustainable desalination technology, yet its energy efficiency remains bottlenecked by the intrinsically high enthalpy of water evaporation. Here, we engineer a covalent organic framework (COF)-based membrane with a hierarchical micrometer-to-angstrom architecture to precisely regulate water behavior for efficient activation and evaporation. With competitive interface/solution nucleation kinetics, confined interfacial growth of COF on vertical microchannels drives a re-entrant crystallinity transition, yielding uniform COF lattices with ordered water-binding sites. Critically, experimental and theoretical investigations reveal that angstrom-scale hydrophobic/hydrophilic motifs within the COF synergistically promote activated water states featuring weak hydration and rapid diffusion behavior, thereby maximizing intermediate water domains and reducing the evaporation enthalpy to only 30% of that of bulk water. Consequently, the engineered membrane achieves a high rate of 2.98 kg m-2 h-1 under a moderate thermal gradient (45 °C/25 °C) and maintains stable performance over 240 h of continuous operation. This work establishes a paradigm for manipulating water activation via angstrom-scale texturing in porous materials, paving the way for energy-efficient desalination and beyond.