Constructing Z -Scheme Ni-MOF-74/CoAl-Layered Double Hydroxide Heterojunctions for Enhanced Photocatalytic CO ₂ Reduction

Constructing Z-scheme heterojunctions is crucial for improving the charge localization on the surface of photocatalysts and enhancing photocatalytic reduction performance. Herein, this research proposes a heterostructure construction strategy that utilizes a Nickel-based metal organic framework with MOF-74 topology (Ni-MOF-74) as a structural template for deriving ultrathin CoAl-LDH nanosheets (denoted as 20-NiL). This approach enables precise control over the two-dimensional lamellar morphology and interfacial electronic structure, facilitating electron-hole pair separation and mitigating CoAl-LDH nanosheet aggregation. Under simulated solar irradiation, 20-NiL exhibits a CO production rate of 79.86 μmol·g⁻¹·h⁻¹, representing a 70% enhancement over the pristine components. By comparing the XPS spectra before and after the photocatalytic reaction, we confirm the charge transfer mechanism of the Z-scheme heterojunction: the binding energies of Co and Al increase, while that of Ni decreases, indicating the transfer of electrons (e⁻) from CoAl-LDH to Ni-MOF-74 upon light irradiation. In situ Fourier transform infrared spectroscopy combined with Soft X-ray absorption spectroscopy elucidates the 2e⁻ pathway for CO₂ conversion to CO through the dominant intermediates COOH* and CO*. This work is expected to provide helpful reference for the development of Z-scheme heterojunction photocatalysts and the investigation of their charge transfer kinetics.