Carbon-Confined Nickel Phosphide with Highly Active Ni^δ+–P^δ−Pairs for Near-Quantitative Conversion of Cellulose to Sorbitol

The development of recyclable heterogeneous bifunctional catalysts for the efficient conversion of cellulose into high-value platform chemicals is still a significant challenge. Herein, the preparation of carbon-nanosheet-encapsulated nickel phosphide catalysts was performed via solvent evaporation self-assembly and alkali activation, and the as-synthesized catalyst efficiently (3 h) hydrolyzes and hydrogenates microcrystalline cellulose to sorbitol with a sorbitol yield exceeding 90%. As a bifunctional catalyst, nickel phosphide (Ni^δ+–P^δ–) facilitates the heterolytic cleavage of H₂, simultaneously generating in situ acidic H^δ+ species for hydrolysis and hydridic H^δ– species for the hydrogenation of C═O bonds. Unlike conventional catalysts with spatially separated functionalities, this concurrent process avoids intermediate accumulation and side reactions during cellulose conversion. Furthermore, encapsulation by carbon nanosheets suppresses phosphorus leaching under hydrothermal conditions, endowing the catalyst with balanced durability and activity. This work provides fundamental insights into hydrogen activation by transition metal phosphides and advances the design of bifunctional catalysts integrating both acidic and hydrogenation functionalities.