Electronic and Steric Modification of Ni Nanoparticle Surface via N-Doped Carbon Layers Enables Highly Selective Semihydrogenation of Alkynes

The selective semihydrogenation of alkynes to alkenes is of great importance in the chemical industry. However, it remains a big challenge to achieve high catalytic activity and selectivity simultaneously, which calls for developing efficient and selective catalysts. In this work, we develop a spatially confined Ni catalyst with Ni nanoparticles (NPs) as the core and N-doped carbon layers as the shell. The core–shell structure not only effectively protects Ni NPs from aggregation to substantially boost the stability but also creates the steric and electronic effects for Ni NP surface via an intimate interfacial interaction with N-doped carbon layers. As a result, the resultant catalyst exhibited both high activity and selectivity for semihydrogenation of alkynes to alkenes. A broad set of terminal and internal alkynes were efficiently reduced to their respective alkenes in a highly selective manner, and various functional groups were well tolerated. Remarkably, these spatially confined Ni NPs are applicable for scale-up synthesis, demonstrate high stability, and could be readily separated for successive reuses without obvious decay in either activity or selectivity. Comprehensive characterizations and control experiments jointly demonstrate the key role of N-doped carbon layers around Ni NPs for improving the catalytic activity, selectivity, and stability.