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

Photocatalytic synthesis of hydrogen peroxide (H 2 O 2 ) from oxygen (O 2 ) 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 (H 2 L 1 ) with a [(H 2 L 2 )Re I (CO) 3 Cl] (H 2 L 2 = 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 H 2 O 2 from O 2 of 8.50 mmol g cat –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 [Re I (CO) 3 Cl] moiety within the framework structure. In situ electron paramagnetic resonance (EPR) spectroscopy suggests that photocatalytic H 2 O 2 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.