Fully exposed cobalt nanoclusters anchored on nitrogen-doped carbon synthesized by a host-guest strategy for semi-hydrogenation of phenylacetylene

•The fully exposed cobalt nanoclusters over nitrogen-doped carbon support were created by a host–guest strategy.•This catalyst shows excellent catalytic efficiency in semi-hydrogenation of phenylacetylene.•DFT calculations reveal that the high selectivity originates from the highly exposed cobalt nanoclusters.•A wide substrate scope and a broad functional-group tolerance were also demonstrated.