Built-in electric field mediated S-scheme charge migration and Co-N4(II) sites in cobalt phthalocyanine/MIL-68(In)-NH2 heterojunction for boosting photocatalytic nitric oxide oxidation

The novel Molecular Cobalt Phthalocyanine modified MIL-68(In)-NH2 S-scheme Heterojunction exhibit excellent NO oxidation performance with low toxic NO2 generation. The enhanced activity can be attributed to the Strong O2 Activation and Enhanced Built-in electric fields [Display omitted] •Molecular-dispersed CoPc/MIL-68(In)–NH2 heterojunction with Co-N4(II) sites has been successfully synthesized.•The enhanced built-in electric field promote an efficient S-scheme charge transfer.•The Co-N4(II) sites displays bifunctional effects for capturing photoexcited electrons and promoting the O2 activation.•Improved NO oxidation efficiency and suppression of toxic by-products are achieved. The efficiency of photocatalytic Nitric Oxide(NO) oxidation is limited by the lack of oxygen(O2) active sites and poor charge carrier separation. To address this challenge, we developed a molecular Cobalt Phthalocyanine modified MIL-68(In)–NH2 photocatalyst with a robust Built-in electric field(BIEF). In the 2 % CoPc-MIN sample, the BIEF strength is increased by 3.54 times and 5.83 times compared to pristine CoPc and MIL-68(In)–NH2, respectively. This BIEF facilitates the efficient S-scheme charge transfer, thereby enhancing photogenerated carrier separation. Additionally, the Co-N4(II) sites in CoPc can effectively trap the separated photoexcited electrons in the S-scheme system. In addition, the Co-N4(II) sites can also serve as active sites for O2 adsorption and activation, promoting the generation of superoxide radical (O2–), thereby driving the direct conversion of NO to nitrate(NO3–). Consequently, the 2 % CoPc-MIN sample exhibits a remarkable photocatalytic NO removal efficiency of 79.37 % while effectively suppressing the formation of harmful by-product nitrogen dioxide(NO2) to below 3.5 ppb. This study provides a feasible strategy for designing high-efficiency O2 activation photocatalysts for NO oxidation.