Dual-site Langmuir-Hinshelwood mechanism in ZnCr-LDH/NH2-UIO66 heterojunction for efficient photocatalytic NO oxidation

Abstract

In this study, we developed a ZnCr-LDH/NH₂-UIO66 heterojunction to enhance photocatalytic NO oxidation through a dual-site Langmuir-Hinshelwood (L-H) mechanism. Nitrogen oxides (NOₓ), including NO, are hazardous environmental contaminants linked to severe air pollution issues such as haze, acid rain, and photochemical smog. The composite catalyst addresses these challenges by synergistically activating NO and O₂ under environmentally relevant conditions, including simulated solar light, ambient temperature, and NO concentrations of 1000 ppb typical of polluted urban areas. The MOF component (NH₂-UIO66) selectively adsorbs NO, while the LDH component (ZnCr-LDH) efficiently activates O₂ to generate reactive oxygen species (ROS). The built-in electric field (BIEF) optimizes charge separation, enabling 71.1 % NO removal efficiency with 97.8 % nitrate selectivity, effectively suppressing toxic NO₂ byproduct formation. This work provides a sustainable strategy for mitigating hazardous NO emissions in air pollution control, bridging material design with environmental remediation.