Designing 1-nm-Thick MOF Nanosheets with Donor–Acceptor Complexes for Photosynthesis of H2O2 Using Water and Dioxygen Only

Artificial photosynthesis of hydrogen peroxide (H2O2) presents a promising environmentally friendly alternative to the industrial anthraquinone process. This work designed ultrathin metal–organic framework (MOF) nanosheets on which porphyrin ligand as an electron donor (D) and anthraquinone (AQ) as an electron acceptor (A) are integrated as the D–A complexes. The porphyrin component allows the MOF nanosheets to absorb full-spectrum solar light while the acceptor AQ motif promotes central aluminum ion coordination, hindering layer stacking to achieve a thickness of 1.0 nm. The ultrathin D–A design facilitates the separation of electrons from the MOF skeleton to the AQ motif, which induces the direct two-electron oxygen reduction reaction (ORR) mediated by the reversible redox couple of AQ-AQH2 and multielectron water oxidation reaction (WOR) driven by holes remaining on the porphyrin part. In O2-saturated water, the ultrathin MOF nanosheets outperformed the AQ-free bulk and multilayered counterparts by 2.9 and 2.6 times in H2O2 production, respectively, achieving the apparent quantum yield of 4.8% at 420 nm. It also surpasses other benchmark photocatalysts, including the typical MOF photocatalyst, MIL-125-NH2, and organic polymeric photocatalysts. The ultrathin D–A MOF photocatalyst generated H2O2 via both two-electron ORR as a major path and two-electron WOR as a minor path. This approach presents a promising strategy for the rational design of efficient nanostructured photocatalysts for solar fuels and chemicals.