Oxygen-Containing Functional Groups in Ni@C(O): Regulating Water-Mediated Pathways for Selective Hydrogenation of Diphenyl Ether to Cyclohexanol

Constructing oxygen-containing functional groups and understanding their catalytic mechanism are crucial for the design of carbon-based catalysts. A Ni@C(O) catalyst rich in oxygen-containing functional groups was prepared by calcining oxygen-rich precursors in a nitrogen atmosphere. This catalyst exhibited a cyclohexanol selectivity of 96.5% in the aqueous phase catalytic conversion of diphenyl ether, which is significantly higher than that of traditional Ni/C catalysts, with selectivity typically below 50.0%. Mechanistic studies reveal that oxygen-containing functional groups promote the participation of water molecules in the reaction, which is key to achieving high selectivity. This effect occurs because oxygen-containing functional groups induce the adsorption of diphenyl ether molecules on the catalyst surface in a planar twisted configuration. The resulting adsorption geometry provides a favorable spatial environment for water molecules to attack the ether bond in diphenyl ether, thereby driving the selective formation of cyclohexanol. Furthermore, the Ni@C(O) catalyst maintained stable performance for 200 h in a fixed-bed continuous-flow experiment and exhibited broad applicability to a range of analogous substrates containing ether bonds.