Enhanced CO₂ photoreduction in pure water systems by surface-reconstructed asymmetric Mn–Cu sites

Metal-organic frameworks (MOFs) with abundant pores are excellent adsorbents for metal ions. However, the subsequent treatment of used MOFs and their reutilization still lack promising solutions. Herein, the surface-restructured Mn-doped Cu₂O (RM-Cu₂O) catalyst containing asymmetric Mn−Cu sites is prepared by glucose reduction using the spent Cu-based MOF (HKUST-1) as the precursor. The RM-Cu₂O catalyst shows good potential in tunable photocatalytic syngas (CO and H₂) production in a pure water system. The syngas ratios can be tuned from ∼1:2 to ∼1:1 by increasing CO production. DFT calculations and photoelectrochemical tests confirm that the asymmetric Mn−Cu sites on the RM-Cu₂O catalyst accelerate the photogenerated charge transport and optimize CO₂ adsorption and activation. In situ irradiation X-ray photoelectron spectroscopy is conducted to investigate the dynamic charge transport and reactions on the RM-Cu₂O catalyst. Based on in situ Fourier transform infrared spectroscopy and simulations, the mechanism of photocatalytic syngas production is elucidated. This work provides a promising solution for the resource utilization of the spent MOFs-based adsorbents and photocatalytic energy development. © 2024 Elsevier B.V.