Spatially Decoupled Capture-Conversion Architectures for Photocatalytic Uranium Extraction from Dilute Wastewater

Integrating adsorption motifs with photocatalytic units into capture-conversion architectures can, in principle, enhance photocatalytic uranium extraction from dilute wastewater. However, whether their spatial relationship promotes synergy or causes mutual interference remains unclear. Here, we employ a family of isomeric covalent organic frameworks (TpBpy4, TpBpy5, and TpBpy6) as a model platform to program site-overlapped/proximate (TpBpy4 and TpBpy5) and site-decoupled (TpBpy6) relationships between UO₂²⁺ adsorption motifs and photocatalytic oxygen reduction sites. The site-decoupled TpBpy6 suppresses mutual interference between UO₂²⁺ capture and oxygen reduction, sustaining in situ photocatalytic H₂O₂ generation and enabling continuous conversion of captured UO₂²⁺ into insoluble studtite ((UO₂)(O₂)·4H₂O), whereas TpBpy4 and TpBpy5 suffer from UO₂²⁺-induced suppression of photocatalytic activity that interrupts the capture-conversion cycle. Under low-ppm UO₂²⁺ concentrations, TpBpy6 delivers a 1.83-fold higher extraction efficiency than the site-overlapped analogue TpBpy5 and achieves a capacity of 51.7 mg g^-1 from actual dilute mining wastewater. This work reveals that overall performance is governed by the interplay between adsorption and photocatalytic sites and establishes a spatial decoupling design principle for minimizing mutual interference while preserving functional synergy in photocatalytic extraction systems for valuable resource recovery from dilute effluents.