Photocatalytic Production of Hydrogen Peroxide Using MOF Materials

The previous chapters demonstrate the solar energy conversion via water splitting, CO2 reduction, and nitrogen fixation. Apart from the above promising processes, hydrogen peroxide (H2O2) can also be synthesized photocatalytically as a solar fuel from O2 using effective photocatalysts. Metal–organic frameworks (MOFs) are hybrid porous materials consist of organic linkers and metal oxide clusters and have become an alternative to conventional inorganic porous materials, such as zeolite and silica, owing to their unique properties. Synthesis of H2O2 from O2 reduction reaction using MOFs is attractive and promising. In this chapter, the H2O2 production through visible light induced O2 reduction by a MOF; MIL-125-NH2 coupled with oxidative reaction of benzyl alcohol was achieved in a single-phase system composed of acetonitrile and benzyl alcohol. The catalytic activity could be greatly enhanced by deposition of NiO nanoparticles onto the MOF. For better separation and collection of the formed H2O2, photocatalytic H2O2 production in a two-phase system composed of benzyl alcohol and water (BA/water) was creatively designed and realized spontaneous separation of the MOFs in the BA phase and the H2O2 in the aqueous phase. The higher concentration of H2O2 was obtained in this two-phase system catalyzed by the hydrophobic linker-alkylated MIL-125-NH2, compared with the single-phase system. Furthermore, enhanced photocatalytic activity was observed using the hydrophobic cluster-alkylated MIL-125-NH2 due to its maintained surface area for the faster diffusion of reactants and products. These works creatively developed the application of MOFs in the field of new energy production.