Dual heterojunction engineering in SiC/Ni-MOF derivative hybrids for boosting photocatalytic CO₂ reduction with H₂O

Heterojunction construction has been widely regarded as a pivotal strategy for enhancing photocatalytic CO₂ conversion of Ni-MOF and employing the post-synthetic modification (PSM) strategy can further improve the electron transport efficiency and increase the reaction active sites of MOF-based materials. Hence, in this study, a novel SiC/Ni-MOF derivatives dual heterojunction (Ni/C/SiC/Ni-MOF) with Schottky and Type-II was designed and synthesized via an in-situ hydrothermal followed by pyrolysis in N₂ atmosphere. The metallic Ni nanoparticles formed during pyrolysis acted simultaneously as active sites and electron accumulation hubs. Furthermore, the strong interfacial interactions of SiC/Ni-MOF type-II heterojunction and Schottky barrier between Ni and SiC facilitated efficient charge transfer across the interfaces. The coexistence of defective C and graphitic C optimized the adsorption of CO₂ and electron transport. In-situ DRFTIR analysis confirmed the formation of key intermediates *COOH and *CHO, which are vital for CO₂ conversion to CO and CH₄. Density functional theory (DFT) calculations revealed the electron transfer route with the existence of internal electron field (IEF). Meanwhile, the energy level matching among graphitic C, SiC and Ni resulted in the accumulation of electrons on metallic Ni. Under simulated sunlight irradiation, the evolution rates of CO and CH₄ on SiC/Ni-MOF pyrolyzed at 400 °C (S/N-400) achieved 7.42 μmol·g^-1·h^-1 and 16.75 μmol·g^-1·h^-1, respectively with a CH₄ selectivity as high as 90.0%. This work provides a feasible strategy for constructing dual heterojunction with synergistic effects to accomplish efficient CO₂ conversion.