The high photocatalytic activity of {110}-bound Cu2O rhombic dodecahedra suggests that the photogenerated electrons, holes, and radicals can be utilized to catalyze some organic transformations. Compared to Cu2O cubes and octahedra, Cu2O rhombic dodecahedra give the best photocatalytic hydroxylation yield of 4-methoxyphenylboronic acid to 4-methoxyphenol at 95% in water and at room temperature in the presence of a hole acceptor, showing that surface control is also important to the catalyst performance. Cu2O rhombic dodecahedra also give generally excellent yields toward a variety of arylboronic acids. Arylboronic esters are less efficient choices for this reaction. Free radical scavenger test and electron paramagnetic resonance measurements indicate that photogenerated superoxide radicals are produced and added to arylboronic acids to form phenols. This work shows that ionic solids can find use in photo-assisted organic reactions.

4-Nitrophenylacetylene-functionalized Cu 2 O rhombic dodecahedra and cubes have been used to photocatalyze aryl sulfide oxidation generating aryl sulfoxides. With an oxygen supply and light from a blue light-emitting diode (LED), the reaction can be completed in 12 h with a water and methanol mixed solution. Generally high product yields and excellent product selectivity of sulfoxides over sulfones were achieved. In particular, a thioanisole to methyl phenyl sulfoxide yield of 98% was obtained. A mechanistic study has revealed that photogenerated electrons, holes, and superoxide radicals are involved in the oxidation reaction. The benefit of simple photocatalyst preparation and molecular functionalization to boost catalytic performance shows that surface-controlled ionic solids can be very effective photocatalysts for some organic transformations.