Microdroplet-Enabled Interfacial Electron Transfer Accelerates Schiff Base Condensation for Ultrafast Covalent Organic Framework Synthesis

Imine-linked covalent organic frameworks (COFs) are attractive crystalline porous materials, yet their synthesis is kinetically limited by sluggish acid-catalyzed Schiff base condensation. Here we report a microdroplet-driven strategy that enables rapid and scalable COF formation via an unconventional interfacial pathway. Continuous ultrasonic nebulization of aqueous monomers affords crystalline imine-linked COFs within minutes at room temperature, without catalysts or organic solvents, achieving reaction rates orders of magnitude higher than batch synthesis. Mechanistic studies reveal the gas-liquid interface of microdroplets as an electronically active reaction zone, where interfacial electron transfer generates radical and anionic nitrogen species that trigger a nonclassical condensation mechanism. Interfacial enrichment, hydrogen-bond symmetry breaking, and strong electric fields cooperatively lower activation barriers and promote dehydration-driven framework growth. This general and scalable platform transforms the air-water interface into an active electronic reactor, establishing a new paradigm for framework synthesis and interfacial reaction acceleration.