Facile synthesis of hydrochar supported copper nanocatalyst for Ullmann C-N coupling reaction in water

The exploration of inexpensive and stable heterogeneous catalysts and application of green solvents for Ullmann C-N coupling reaction remain challenging. We present a facile fabrication of copper nanoparticles on hydrochar as prepared from natural, inexpensive and renewable chitosan together with in-situ reduction of copper salt in a one-pot hydrothermal carbonization process. The copper nanoparticles were uniformly dispersed on hydrochar by choosing block copolymer F127 as surfactant. Moreover, maleic acid was introduced to improve the hydrophilicity of hydrochar. The most active copper nanocomposite catalyst, that is, Cu/HCS-MA-F127, exhibited excellent catalytic activity for Ullmann C-N coupling reaction in water. The nature of the Cu/HCS-MA-F127 was characterized by FTIR spectroscopy, TG, XRD, SEM and XPS. Moderate to excellent yields of aimed products were gained by using this catalytic strategy. Moreover, the Cu/HCS-MA-F127 catalyst can be reused by simple centrifugal recovery with a stable performance.