A Cerium-Naphthazarin Catecholate MOF as a Heterogeneous Photocatalyst for Selective Functionalization of Alkanes.

In this work we have successfully synthesized a series of novel semiconducting 2D catecholate metal-organic frameworks (MOFs) based on naphthazarin ligands by utilizing unraveled metal-acetyl acetonate linkage chemistry. The synthesized Ce-Naph MOF exhibited excellent light absorption properties and chemical stability across various solvents. Its insoluble and stable framework, combined with an optimal band gap, enabled its use as a photocatalyst for organic transformations. For the first time, Ce-Naph MOF is explored as a heterogeneous catalyst for photocatalytic applications specifically for the selective C-H amination of alkanes, achieving yields of up to 89% under ambient conditions. We propose that the initial metal-to-ligand charge transfer in Ce-Naph MOF, promoted by light, is essential for forming an active alkoxy-Ce(IV)-species. This species subsequently undergoes ligand-to-metal charge transfer to generate the alkoxy radical, which acts as a hydrogen atom transfer reagent to activate alkanes. Furthermore, Ce-Naph MOF demonstrated long-term cyclic stability, maintaining its catalytic activity and structural integrity over five cycles, highlighting its durability as a heterogeneous catalyst. We are confident that this straightforward and practical methodology opens new avenues for industrial applications, significantly advancing the fields of metal catalysis, photocatalysis, and sustainable chemistry.