Sub‐Nanometer Mono‐Layered Metal–Organic Frameworks Nanosheets for Simulated Flue Gas Photoreduction

Abstract The dilemma between the thickness and accessible active site triggers the design of porous crystalline materials with mono‐layered structure for advanced photo‐catalysis applications. Here, a kind of sub‐nanometer mono‐layered nanosheets (Co‐MOF MNSs) through the exfoliation of specifically designed Co₃ cluster‐based metal–organic frameworks (MOFs) is reported. The sub‐nanometer thickness and inherent light‐sensitivity endow Co‐MOF MNSs with fully exposed Janus Co₃ sites that can selectively photo‐reduce CO₂ into formic acid under simulated flue gas. Notably, the production efficiency of formic acid by Co‐MOF MNSs (0.85 mmol g⁻¹ h⁻¹) is ≈13 times higher than that of the bulk counterpart (0.065 mmol g⁻¹ h⁻¹) under a simulated flue gas atmosphere, which is the highest in reported works up to date. Theoretical calculations prove that the exposed Janus Co₃ sites with simultaneously available sites possess higher activity when compared with single Co site, validating the importance of mono‐layered nanosheet morphology. These results may facilitate the development of functional nanosheet materials for CO₂ photo‐reduction in potential flue gas treatment.