Thiol-induced in situ synthesis of bifunctional Au-SH/SO3H-COP enables efficient and recyclable alkyne hydration

Abstract

A novel and efficient immobilized Au nanoparticle catalyst, Au-SH/SO₃H-COP, has been synthesized via the in situ reduction of Au³⁺ ions by thiol groups within a thiol-functionalized covalent organic polymer (SH-COP). This approach leverages the thiol groups as intrinsic reductants, eliminating the need for external agents. Simultaneously, during Au nanoparticle formation, anchored sulfonic acid (–SO₃H) sites are generated, which function as Brønsted acid co-catalysts to synergistically enhance catalytic performance. Characterization results confirmed the formation of uniformly dispersed Au nanoparticles with a narrow size distribution centered at 2–3 nm. The covalent anchoring of nanoparticles to the SH-COP support through unreacted thiol groups effectively prevents aggregation and leaching. For the model hydration of phenylacetylene, Au-SH/SO₃H-COP exhibited excellent catalytic activity, achieving 92% yield without additional acid additives. Moreover, it displayed broad substrate compatibility across diverse alkynes (aryl and aliphatic), affording 84–94% yields. The catalyst also showed high recyclability, retaining 89% yield after six cycles with negligible Au leaching, underscoring its robustness and reusability.