Cuprous-Sulfide-Nanoplate-Catalyzed Click Chemistry for In Situ Construction of Covalent Organic Polymer Heterostructures for Efficient Photocatalytic Reduction and Removal of U(VI)

In this study, a core-shell heterostructure of cuprous sulfide (Cu₂S) nanoplates and covalent organic polymers (COPs) (Cu₂S@COP) was constructed in situ by a Cu₂S-catalyzed azide-alkyne reaction for efficient reduction and rapid removal of U(VI) from uranium mine wastewater. The simple in situ synthesis of heterojunctions through click chemistry reactions can create a tight bond at the interface and evade the laborious process of conventional composites. The different Fermi energy levels of Cu₂S and COP induce the formation of a built-in electric field within the core-shell heterojunction, and the photogenerated charge transfer from the COP to Cu₂S nanoplate results in a substantial boost in the efficiency of the photocatalytic reduction of U(VI). The Cu₂S@COP heterojunction demonstrates a high U(VI) removal capacity of 1164.6 mg g^-1 without the need of a sacrificial agent, which is 2.08 times higher than Cu₂S nanoplates, 3.02 times higher than COP, and better than most other previous heterostructures. The present photocatalytic method involves good specificity and achieves a high U(VI) removal efficiency of 85.9% from uranium mine wastewater. The in situ preparation of the Cu₂S@COP core-shell heterojunction via click chemistry provides a new design concept for composite construction and presents a novel strategy to modulate the photocatalytic activity for contaminant management.