Pore-Confined π-Chromophoric Tetracene as a Visible Light Harvester toward MOF-Based Photocatalytic CO Reduction in Water.

Integrating photoactive π-chromophoric guest molecules inside the MOF nanopore can result in the emergence of light-responsive features, which in turn can be utilized for developing photoactive materials with inherent properties of MOF. Herein, we report the confining of π-chromophoric tetracene () molecules inside the nanospace of postmodified Zr-MOF-808 () with MBA molecules (MBA = 2-(5'-methyl-[2,2'-bipyridine]-5-yl)acetic acid) for effectively utilizing its light-harvesting properties toward photocatalytic CO reduction. The confinement of the molecules as a photosensitizer and the covalent grafting of a catalytically active [Re(MBA)(CO)Cl] complex, postsynthetically, result in a single integrated catalytic system named . Photoreduction of CO over showed the evolution of 805 μmol g CO with 99.9% selectivity after 10 h of continuous visible light irradiation in water without any additional sacrificial electron donor and having the apparent quantum efficiency of 1.3%. In addition, the catalyst demonstrated an appreciable activity even under direct sunlight irradiation in aqueous medium with a maximum production of 362.7 μmol g CO, thereby mimicking artificial photosynthesis. Moreover, electron transfer from to the catalytic center was supported by the formation of photoinduced radical cation, as inferred from in situ UV-vis spectra, electron paramagnetic resonance (EPR) analysis, and transient absorption (TA) studies. Additionally, the in situ diffuse reflectance infrared Fourier transform (DRIFT) measurements support that the photoreduction of CO to CO proceeds via *COOH intermediate formation. The close proximity of the light-harvesting molecule and catalytic center facilitated facile electron transfer from the photosensitizer to the catalyst during the CO reduction.