UO4·2H2O from Depleted Uranium Waste: A Regenerable Solid FLP Catalyst with Negligible Radioactivity for Selective Aniline Oxidation

The accumulation of depleted uranium (DU), a byproduct of nuclear energy production, poses significant environmental concerns. Converting DU into functional catalysts represents a promising strategy for its resource valorization. Herein, we report a ²³⁸U-based catalyst, UO₄·2H₂O, with negligible radioactivity, synthesized from DUF₆-derived α-U₃O₈ via a dissolution–precipitation method, enabling selective oxidation of aniline to nitrosobenzene, azobenzene, and azoxybenzene by solvent tuning. Structural and mechanistic studies reveal that surface defects form frustrated Lewis pairs (FLPs). Its Lewis acidic U⁶⁺ sites strengthen the U═O bond and shorten its length, enhancing electron-withdrawing ability and promoting aniline adsorption, while the basic oxygen-vacancy sites facilitate H₂O₂ activation and singlet oxygen generation, thereby promoting aniline oxidation. Notably, the catalyst is regenerable via calcination-reprecipitation for up to 60 cycles, with an E-factor well below the fine chemical benchmark. This work provides a scalable strategy for DU valorization and a practical platform for the synthesis of nitrogen-containing fine chemicals.