Z-scheme MIL-125-NH2(Ti)/PdTCPP heterojunction accelerates carrier separation via Au NPs electron bridge for efficient photocatalytic NO removal and hydrogen evolution

Under the global dual-carbon goal, photocatalysis technology is being employed as a green technology for NO removal and hydrogen production. However, the application of photocatalysts is often limited by the weak response to visible light and the low separation efficiency of photogenerated carriers. In this paper, we designed a simple and efficient photocatalyst Au@NM-125/PdTCPP for NO removal and hydrogen evolution. By adding PdTCPP molecule with excellent light absorption ability combine with MIL-125-NH(Ti), the introduction of PdTCPP expands the absorption range of visible light. On the other hand, the introduction of Au NPs with surface plasmon resonance effect promotes electron transport between PdTCPP and MIL-125-NH(Ti), thus greatly improving the photocatalytic performance. Compared with the NO removal efficiency of the original NM-125 (22.06 %), the NO removal rate of NM-125/PdTCPP was 63.72 %, while the NO removal rate of Au@NM-125/PdTCPP was the highest, reaching 73.23 %. What’s more, Au@NM-125/PdTCPP also demonstrated excellent hydrogen evolution performance (12.659 mmol/g, in 4 h), with a hydrogen evolution effect 2.14 times that of NM-125/PdTCPP (5.911 mmol/g, in 4 h) and 6.85 times that of the initial NM-125 (1.848 mmol/g, in 4 h). Based on the results of UV-Vis spectroscopy, Mott-Schottky and XPS spectrum, we proposed a possible photocatalytic mechanism, the suitable band gap value of MIL-125-NH(Ti) and PdTCPP makes them form a Z-scheme heterojunction, where electrons flow from PdTCPP to MIL-125-NH(Ti), and Au NPs acts as an electron bridge to promote more electron transfer, thus improving the photocatalytic performance. It is a practicable strategy to achieve excellent photocatalytic performance by combining metalloporphyrin molecules as semiconductors directly with MOFs to form heterojunctions and adding Au NPs as electronic bridges, which is also valuable for environmental remediation and energy production.