Fe-Based Metal-Organic Frameworks for Highly Selective Photocatalytic Benzene Hydroxylation to Phenol

Phenol is one of the most important chemicals in industry. One-step selective benzene hydroxylation is an attractive yet challenging method for phenol production, especially when such a reaction can be driven by solar energy. Herein, we reported that a highly selective benzene hydroxylation to phenol can be achieved over two Fe-based metal organic frameworks [MIL-100(Fe) and MIL-68(Fe)] under visible light irradiations using hydrogen peroxide (H2O2) as an oxidant. An optimal benzene conversion of 30.6% was achieved with a H2O2:benzene ratio of 3:4 over MIL-100(Fe) after 24 h irradiations. ESR results and the kinetic studies suggested that a successful coupling of the photocatalysis of Fe-O clusters in Fe-based metal organic frameworks (MOFs) with a Fenton-like route is involved in this benzene hydroxylation process. The comparison of the reaction over MIL-100(Fe) and MIL-68(Fe) reveals that the structure of MOFs significantly influences the photocatalytic efficiency. Because the composition and the structure of MOFs are highly tunable, this study highlights the great potential of using Fe-based MOFs for photocatalytic benzene hydroxylation to form phenol, which may result in an economical, sustainable, and thus green process for phenol production.