Copper Single-Atom Catalyst for Efficient C─S Coupling in Thioether Synthesis

Carbon-heteroatom cross-coupling reactions have become indispensable tools in synthetic chemistry. However, the formation of carbon-sulfur (C─S) bonds, which are essential for producing thioethers used in pharmaceuticals, agrochemicals, and advanced materials, remains significantly underdeveloped. Industrial C─S coupling methods still rely on expensive, homogeneous catalysts that suffer from poor recyclability and are susceptible to sulfur-induced deactivation. In this work, we report a copper single-atom catalyst, where Cu sites are atomically dispersed on mesoporous graphitic carbon nitride, to enable efficient, selective, and recyclable C─S cross-coupling reactions under mild conditions and on a gram scale. The catalyst exhibits excellent resistance to thiol poisoning and maintains high performance over multiple catalytic cycles. Advanced characterization techniques, including aberration-corrected electron microscopy, X-ray absorption spectroscopy, and single-atom-sensitive electron energy loss spectroscopy, confirm the atomic dispersion and stable coordination environment of Cu sites. Combined with density functional theory simulations and radical scavenging experiments, our mechanistic investigations support a concerted oxidative addition pathway, which excludes radical intermediates. These results provide key insights into heterogeneous C─S coupling and demonstrate the power of single-atom catalysts in addressing long-standing challenges in sulfur chemistry, paving the way toward greener and more scalable processes for fine chemical and pharmaceutical synthesis.