Highly efficient photocatalytic conversion of CO2 achieved by constructing core–shell Z-scheme Bi2MoO6@COF heterojunction

Abstract

The conversion of CO₂ into hydrocarbon fuels through photocatalytic technology contributes to a sustainable carbon cycle. However, the use of noble metals and photosensitizers in previous studies has raised costs while the slow charge transfer rates during the photocatalytic process have diminished CO₂ conversion efficiency. Therefore, this study investigated a core–shell Bi₂MoO₆@COF photocatalyst constructed by combining Bi₂MoO₆ nanoflower balls with the organic covalent framework TpPa-2-COF, which facilitated the photocatalytic reduction of CO₂ under water vapor conditions. Additionally, the Z-scheme heterojunction formed between Bi₂MoO₆ and TpPa-2-COF promoted interfacial charge transfer, enhancing the separation efficiency of electrons and holes. The optimized Bi₂MoO₆@COF photocatalyst exhibited excellent catalytic performance in CO₂ reduction reactions, achieving a CO reduction rate of 12.71 μmol·g⁻¹·h⁻¹ and a CH₄ reduction rate of 5.5 μmol·g⁻¹·h⁻¹, which were approximately 2.73 times and 1.42 times higher than those of Bi₂MoO₆, respectively. Furthermore, the active species capture experiment, electron paramagnetic resonance (EPR) and photoelectrochemical techniques were employed to propose the photocatalytic mechanism of CO₂ reduction for as-prepared Z-scheme Bi₂MoO₆@COF heterojunction.