Sieving aquatic uranium for photocatalytic hydrogen evolution with covalent organic frameworks

Uranium and hydrogen represent two of vital energy carriers in modern energy systems, while with distinct environmental impacts. The uranium-containing wastewater, though possibly causing ecological dangers, may also serve as the resource of uranium and hydrogen from the prospective of science and technology. In this study, we showed that covalent organic frameworks (COFs) with specific structures could drive photo-splitting of uranium-containing water into hydrogen. When exposed to light irradiation, benzotriazole-based COF could coordinate and photo-reduce uranium ions for photocatalytic hydrogen evolution from water. The reaction rate was sensitive to the content of uranium ions in water, and gave the maximal of 34.53 mu mol h(- 1) (3 mg) for water containing 2.5 ppm uranium ions, being much superior to the frequently-reported benzothiadiazole-based COF (2.85 mu mol h(- 1) (3 mg)). This unique heteroatomic effect should be due to the enhanced exciton dissociation and charge carrier migration capacity from benzotriazole motif. In water containing 450 ppm uranium ions, benzotriazole-based COF exhibited a uranium adsorption capability as high as similar to 1.86 g g(- 1) within a broad pH range of 3 -9. Thus, this study may not only highlight the crucial roles of aqueous metal ions in photocatalytic hydrogen evolution, but also offer a potential solution for sieving uranium to directly split water into hydrogen in the absence of noble metals.