Photocatalytic Synthesis of Hydrogen Peroxide by Rhenium Modified Metal–Organic Frameworks Incorporating Bianthracene Ligands

Photocatalytic synthesis of hydrogen peroxide (H2O2) from oxygen (O2) is a challenging process. Metal–organic framework (MOF) materials are emerging photocatalysts with potential tunable light absorption properties. Herein, we report a rhenium (Re) modified Zr-based MOF, Re10-MFM-67, in which active Re sites are incorporated into MFM-67 by partial replacement of 9,9′-bianthracene-10,10′-dicarboxylic acid (H2L1) with a [(H2L2)ReI(CO)3Cl] (H2L2 = 2,2′-bipyridine-5,5′-dicarboxylic acid) moiety. Re10-MFM-67 (10 refers to the molar percentage content of Re complex within the material) exhibits broadband light absorption with an exceptional rate of formation of H2O2 from O2 of 8.50 mmol gcat–1 h–1 and a record turnover frequency (TOF) of 28.7 h–1 under visible light irradiation (λ > 400 nm). Synchrotron powder X-ray diffraction (SPXRD) and neutron powder diffraction (NPD) confirm the structure of Re10-MFM-67, and together with extended X-ray absorption fine structure (EXAFS) analysis establish the coordination environment and binding of the [ReI(CO)3Cl] moiety within the framework structure. In situ electron paramagnetic resonance (EPR) spectroscopy suggests that photocatalytic H2O2 generation on Re10-MFM-67 occurs via a two-step oxygen reduction reaction (ORR) pathway with the superoxide anion formed as an intermediate. This study promotes the design of MOF-based photocatalysts with conjugated ligands for efficient photosynthesis.