Unlocking photocatalytic NO removal potential in an S-type UiO-66-NH2/ZnS(en)0.5 heterostructure

Abstract

The contamination of nitric oxide presents a significant environmental challenge, necessitating the development of efficient photocatalysts for remediation. Conventional heterojunctions encounter obstacles such as large contact barriers, sluggish charge transport, and compromised redox capacity. Here, we introduce an innovative S-type heterostructure photocatalyst, UiO-66-NH₂/ZnS(en)_0.5, designed specifically to overcome these challenges. The synthesis, employing a unique microwave solvothermal method, strategically aligns the lowest unoccupied molecular orbital of UiO-66-NH₂ with the highest occupied molecular orbital of ZnS(en)_0.5, fostering the formation of a stepped heterojunction. The resulting intimate interface contact generates a built-in electric field, facilitating charge separation and migration, as evidenced by time-resolved photoluminescence spectroscopy and photoelectrochemical tests. The abundant active sites in the porous UiO-66-NH₂ counterpart provide adsorption and activation sites for nitrogen monoxide (NO) oxidation. Performance evaluation reveals exceptional photocatalytic NO removal, achieving 70% efficiency and 99% selectivity toward nitrates under simulated solar illumination. Evidence from X-ray photoelectron spectroscopy and trapping experiments supports the effectiveness of the S-type heterostructure, showcasing refined reactive oxygen species, particularly superoxide. Thus, this study introduces a new perspective on advanced NO oxidation and unlocks the potential of S-scheme heterojunctions to refine reactive oxygen species for NO remediation.