Assembling MOF-Based (NH₄)_0.8TiOF_2.8@Fe-pyz p-n Heterojunction Through L-Cysteine for CO₂ Photoreduction

Metal organic frameworks (MOFs) have been widely studied in photocatalytic CO₂ reduction reaction (CO₂RR). However, pristine MOFs exhibit low utilization of light, severe recombination of photogenerated carriers and low intrinsic photocatalytic efficiency. In response to the above issues, this paper constructs (NH₄)_0.8TiOF_2.8@Fe-pyz p-n heterojunction photocatalysts through self-assembling L-cysteine for photocatalytic CO₂RR. This composite photocatalyst exhibits excellent photocatalytic activity in reducing CO₂ to high value-added products (HCOOH, CO and CH₄). Through experimental characterization and density functional theory (DFT) calculations, the structure-activity relationship between the crystal structure, the band structure, the photogenerated carrier separation and the catalytic performance of (NH₄)_0.8TiOF_2.8@Fe-pyz was systematically studied, revealing that the built-in electric field in the interface of the p-n heterojunction promotes the photogenerated carrier separation, and the active centers are clarified for CO₂ reduction half-reaction on (NH₄)_0.8TiOF_2.8 and H₂O oxidation half-reaction on Fe-pyz separately. This work demonstrates that rational design of heterojunctions can regulate the structure-activity relationship and open up a new avenue for the fabricating of highly efficient MOF-based CO₂RR photocatalysts.