Methane activation and utilization are among the major challenges of modern science. Methane is potentially an important feedstock for manufacturing value-added fuels and chemicals. However, most known processes require excessive operating temperatures and exhibit insufficient selectivity. Here, we demonstrate a photochemical looping strategy for highly selective stoichiometric conversion of methane to ethane at ambient temperature over silver–heteropolyacid–titania nanocomposites. The process involves a stoichiometric reaction of methane with highly dispersed cationic silver under illumination, which results in the formation of methyl radicals. Recombination of the generated methyl radicals leads to the selective, and almost quantitative, formation of ethane. Cationic silver species are simultaneously reduced to metallic silver. The silver–heteropolyacid–titania nanocomposites can be reversibly regenerated in air under illumination at ambient temperature. The photochemical looping process achieves a methane coupling selectivity of over 90%, a quantitative yield of ethane of over 9%, high quantum efficiency (3.5% at 362 nm) and excellent stability.

甲烷的活化和利用是现代科学的主要挑战。甲烷可能是制造增值燃料和化学品的重要原料。然而，大多数已知方法需要过高的操作温度并且显示出不足的选择性。在这里，我们展示了一种光化学环化策略，用于在环境温度下通过银-杂多酸-二氧化钛纳米复合材料将甲烷高度选择性地化学计量转化为乙烷。该过程涉及在光照下甲烷与高度分散的阳离子银的化学计量反应，这导致形成甲基。产生的甲基的重组导致选择性地和几乎定量地形成乙烷。阳离子银物质同时还原为金属银。银-杂多酸-二氧化钛纳米复合材料可在环境温度下在空气中可逆地再生。光化学环化工艺实现了超过90％的甲烷偶联选择性，超过9％的乙烷定量收率，高量子效率（在362 nm处为3.5％）和出色的稳定性。