Construction of Metallic Hydrogen-Bonded Organic Frameworks for Direct Photocatalytic Reduction of Uranium

Efficient uranium extraction from wastewater is essential for human security and environmental protection, and photocatalytic reduction is perceived as a green and sustainable strategy for effective uranium separation/removal. Herein, four metallic hydrogen-bonded organic frameworks (M-HOFs, M = Co, Ni, Cu, Zn) were constructed through precise metal coordination at the HOF centers. This innovative design enables sacrificial agent-free photocatalytic reduction of soluble U(VI) to insoluble U(IV), where Zn-HOF achieves a maximum removal capacity of 2344.95 mg g^-1 and a removal efficiency of 87% within 60 min. Mechanistic studies combining photoelectronic characterizations and density functional theory calculations reveal the metal-dependent charge separation dynamics and electron transfer efficiency, rationalizing the superior photocatalytic activity of Zn-HOF for uranium reduction. This work proposes a new strategy to modulate the photoactivity of HOFs by metal integration and provides an effective platform for radioactive contaminant remediation.