An S-Scheme MOF-on-MXene Heterostructure for Enhanced Photocatalytic Periodate Activation

Fully understanding the periodate (PI) activation system is still a great challenge, which calls for efficient heterogeneous catalysts with a sophisticated structure. Herein, we developed "MOF-on-MXene" heterostructures. By constructing S-scheme heterostructures MXene/Z67₄₅₀, the internal electric field is generated via the Ti-O-Co bonds at the interface, favoring the excitation of the photogenerated electrons, providing a driving force for accelerating the charge transfer, and enhancing redox performances. Further contributed by the synergy of Ti-O-Co and Co-N₄ bonds, the MXene/Z67₄₅₀ composites exhibit enhanced ability for activating the periodate system to degrade organic pollutants via building a donor-catalyst-acceptor system. In the presence of periodate and light, MXene/Z67₄₅₀ degraded ∼100% of tetracycline hydrochloride (TCH) in only 10 min. The active sites of the heterostructures can react with the periodate and give the intermediate MXene/Z67₄₅₀-PI (*PI). As a result, it efficiently reduced the PI adsorption energy and promoted the decomposition of PI and the formation of holes/electrons, singlet oxygen (¹O₂) as well as hydroxyl radical (•OH). In addition, the MXene/Z67₄₅₀ composites exhibit high stability, reusability, selectivity, and environmental robustness. Our study provides a research direction for rationally designing MXene-based heterojunctions and applying them in the periodate activation system.