Selective Formation of Acetic Acid and Methanol by Direct Methane Oxidation Using Rhodium Single-Atom Catalysts

Atomically dispersed catalysts such as single-atom catalystshavebeen shown to be effective in selectively oxidizing methane, promisinga direct synthetic route to value-added oxygenates such as aceticacid or methanol. However, an important challenge of this approachhas been that the loading of active sites by single-atom catalystsis low, leading to a low overall yield of the products. Here, we reportan approach that can address this issue. It utilizes a metal-organicframework built with porphyrin as the linker, which provides highconcentrations of binding sites to support atomically dispersed rhodium.It is shown that up to 5 wt% rhodium loading can be achieved withexcellent dispersity. When used for acetic acid synthesis by methaneoxidation, a new benchmark performance of 23.62 mmol center dot g(cat) (-1)center dot h(-1) was measured. Furthermore,the catalyst exhibits a unique sensitivity to light, producing aceticacid (under illumination, up to 66.4% selectivity) or methanol (inthe dark, up to 65.0% selectivity) under otherwise identical reactionconditions.