Synergistic defect engineering and phosphonation of porphyrin-decorated UiO-66 for efficient uranium photoreduction

The photocatalytic reduction of U(VI) on semiconductors has been widely investigated as an environmentally friendly and energy-efficient method. However, their practical applications are constrained by the weak affinity of catalysts for uranyl ions and the rapid recombination of photogenerated carriers. To address these challenges, we constructed a porphyrin-decorated UiO-66 photocatalyst (ZBT-P) by integrating BA-induced defect regulation, TCPP sensitization, and post-synthetic phosphonate functionalization. Characterization results demonstrated that the as-synthesized ZBT-P possessed a uniform shape and size distribution with a regular octahedron-like morphology. ZBT-P exhibited high removal efficiency (99.8% under visible-light irradiation) along with excellent stability in complex water bodies across a broad pH range. The introduction of phosphonate groups improved surface hydrophilicity and regulated the interfacial interaction and charge-transfer environment. Meanwhile, this integrated architecture retained the excellent light-trapping capability of TCPP ligands and transformed defect-rich Zr nodes into efficient electron trapping centers, which significantly suppressed the recombination of photogenerated carriers. Mechanistic investigations revealed the coexistence of photoreduced U(IV) species and crystalline metastudtite, a U(VI) uranyl peroxide hydrate ((UO₂)O₂·2H₂O), with photogenerated electrons and superoxide radicals playing important roles in uranium immobilization. Overall, this dual-modification strategy endows ZBT-P with uranium enrichment capability and superior electron transport efficiency, offering great promise for practical environmental remediation.