Amino ligand engineering-induced electronic redistribution in UiO-67 for enhanced visible-light-driven NO oxidation

Amino-density regulation was used to tune the electronic structure of UiO-67. • Diamino ligands induced electron redistribution between Zr nodes and linkers. • UiO-67-2NH 2 showed improved charge separation and interfacial transfer. • NO oxidation was enhanced while NO 2 formation remained at a low level. • Surface NO x intermediates were further converted into nitrate-related species. Functional group engineering of metal-organic frameworks provides a feasible route to tune their electronic structures, yet the specific role of amino ligands in regulating photocatalytic NO oxidation over Zr-based MOFs remains insufficiently clarified. Herein, UiO-67 derivatives with different amino densities were constructed through ligand engineering to investigate the relationship between ligand-induced electronic redistribution and visible-light-driven NO removal. Compared with pristine UiO-67, amino-functionalized UiO-67 exhibited enhanced visible-light absorption, improved charge separation, and reduced interfacial charge-transfer resistance. XPS and band-structure analyses suggest that the introduction of amino groups induces electron redistribution from Zr-oxo nodes toward ligand-related states, resulting in increased electron density near the valence band edge and more favorable photocarrier behavior. Among the prepared samples, UiO-67-2NH 2 showed the highest NO removal efficiency and maintained a relatively low NO 2 release during photocatalytic oxidation. ESR results confirmed the generation of •O 2 − and •OH under visible-light irradiation, while in-situ DRIFTS revealed the formation and evolution of NO + , NO 2 − , and nitrate-related intermediates. These results indicate that photogenerated carriers and reactive oxygen species jointly participate in the stepwise oxidation of NO toward more stable nitrate species. This work provides experimental evidence that amino ligand engineering can remotely modulate the electronic structure of UiO-67 and offers a useful strategy for improving the activity and selectivity of MOF-based photocatalysts for NO removal. Download: Download high-res image (177KB) Download: Download full-size image