Electric Field–Driven Nanoreactor Strategy for Rapid Fabrication of CRO Photocathodes toward Efficient Photoelectrochemical Hydrogen Evolution

ABSTRACT Covalent organic frameworks (COFs) show great promise in photoelectrocatalysis; however, their limited processability and constrained film‐forming capabilities have severely restricted device integration. Herein, we present a universal electric field‐driven nanoreactor electrophoretic deposition strategy for the rapid and mild fabrication of conjugated reticular oligomer (CRO) thin films. This method enables acid catalyst‐free and time‐efficient film growth within several hours by employing the surfactant cetylpyridinium bromide (CPB) as both a nanoreactor and charge carrier. The pyridinium cations (N ⁺ ) of CPB electrostatically anchor the precursor Daf at the micelle interface, confining the reaction within the hydrophobic region and activating the carbonyl groups to facilitate Schiff base condensation. During electrophoretic deposition, CPB simultaneously drives the directed migration and uniform assembly of CRO frameworks onto the conductive substrate. The films exhibit smooth surfaces, robust adhesion, and excellent photoelectrocatalytic hydrogen evolution activity. Specifically, the ITO/CuI/CRO‐DafTp photoelectrode deposited for just 30 s achieves a Δ J of 57.6 µA cm ⁻² at 0.4 V versus RHE. More importantly, this approach demonstrates broad structural adaptability, enabling the successful deposition of three porphyrin‐based CRO materials (CRO‐DafTp, CRO‐DfoTp, and CRO‐SaTp) with comparable performance. This electric field‐assisted micellar strategy provides a versatile, scalable, and green route toward high‐quality COF films for practical photoelectrocatalytic applications.