Synergistic lock-anchor engineered diketopyrrolopyrrole-COFs for efficient photocatalytic uranium extraction

As a key low-carbon energy source, nuclear power plays a vital role in the global transition toward sustainable energy. Photocatalytic uranium extraction from seawater (UES) offers a promising solution to ensure long-term uranium supply but is challenged by ultra-low uranium concentrations and ion interference. To overcome these issues, we design three diketopyrrolopyrrole-based covalent organic frameworks (COFs) via a synergistic π-extended lock and carboxyl-functionalized anchor molecular engineering strategy. Among them, TPy-DPP-COF features a covalently locked π-conjugated structure that enhances planarity, optimizes energy alignment, and minimizes exciton binding energy, thereby promoting charge transfer and suppressing recombination. Concurrently, carboxyl groups enable uranyl-specific coordination and create local electric fields to facilitate charge separation. These features contribute to the outstanding performance of TPy-DPP-COF, which achieves a high uranium adsorption capacity of 16.33 mg g⁻¹ in natural seawater under irradiation, with only 29.3 % capacity loss after 10 cycles, surpassing industrial benchmarks. Density functional theory (DFT) calculations and experimental studies reveal a synergistic photocatalysis-adsorption pathway, with DPP units acting as active sites for uranium reduction. This work highlights a molecular design strategy for developing efficient COF-based photocatalysts for practical marine uranium recovery.