Cobalt-Embedded Metal-Covalent Organic Frameworks for CO₂ Photoreduction

With the pressing urgency to reduce carbon footprint, photocatalytic carbon dioxide reduction has attracted growing attention as a sustainable mitigating option. Considering the important role of catalytic active sites (CASs) in the catalytic processes, control and design of the density and environment of CASs could enhance the catalyst performance. Herein, we report a novel metal-covalent organic framework (MCOF), MCOF-Co-315, featuring earth-abundant Co cocatalysts and conjugation through a covalently bonded backbone. MCOF-Co-315 showed a CO production rate of 1616 μmol g^-1 h^-1 utilizing Ru(bpy)₃Cl₂ as photosensitizer and triethanolamine (TEOA) as sacrificial electron donor with a 1.5 AM filter, vis mirror module (390-740 nm), and irradiation intensity adjusted to 1 sun and an especially outstanding apparent quantum yield (AQY) of 9.13% at 450 nm. The photocatalytic reaction was studied with electron paramagnetic resonance (EPR) spectroscopy, X-ray absorption near-edge structure (XANES), and in situ synchrotron Fourier Transform Infrared (FT-IR) spectroscopy, and an underlying mechanism is proposed.