Nitrogen, Sulfur Co-doped Hollow Carbon-Encapsulated Cu/Co₂P for Selective Oxidation Esterification of Furfurals

With the remarkable capability of encapsulating multifunctional active sites inside, carbon-based materials play vital roles in multifarious chemical transformations such as hydrogenation reactions, oxidation reactions, esterification reactions, etc. Herein, we propose an efficient and facile approach to construct a Cu/Co2P@C-NS catalyst, which consists of nitrogen-sulfur co-doped carbon (C-NS) encapsulated cobalt phosphide (Co2P) and copper double active sites. This approach focuses on the design and preparation of core-shell materials, that is, the ZIF-67 core is coated with an adhesive poly(cyclotriphosphazene-co-4,4 '-sulfonyldiphenol) (PZS) polymer shell. The ZIF-67 core possesses a highly porous structure, coexistence of carbon and nitrogen elements, and uniform dispersion of Co species, making it an ideal template. The heteroatomic PZS polymer with decent coating ability makes it a promising coating material for creating core-shell structures. Additionally, nitrogen species in the PZS polymer could coordinate with Cu2+ to introduce extra Cu sites into the system. The Cu/Co2P@C-NS catalyst prepared from the pyrolysis of the precursor redistributes the surface charge of Co2P by additionally incorporating Cu, which effectively enhances substrate adsorption. As a result, the Cu/Co2P@C-NS catalyst demonstrates good catalytic performance in the oxidative esterification of furfuryl aldehydes. This study presents a reliable and straightforward method for preparing a non-noble-metal catalyst that exhibits high efficiency and activity in the one-pot oxidation and esterification of furfurals to methyl furoates.