Melamine-derived graphitic carbon nitride as a new effective metal-free catalyst for Knoevenagel condensation of benzaldehyde with ethylcyanoacetate

Graphitic carbon nitride was prepared by bulk and hard template pyrolysis of melamine. The prepared g-C3N4 as well as N-doped carbon used for comparison exhibited a reasonable catalytic activity in the Knoevenagel condensation between benzaldehyde and ethylcyanoacetate yielding ethyl--cyanocinnamate (conversion of benzaldehyde up to 100%, yield of the desired product up to 51%). Under the studied reaction conditions, weak basic sites assigned as C-N?C species are responsible for selective formation of the desired product. An increase of tertiary nitrogen content leads to an increase of benzaldehyde conversion with a simultaneous decrease of selectivity towards ethyl--cyanocinnamate due to a higher basicity. Carbon nitride obtained using silica as a hard template allows achieving the highest yield of the desired product (50.9%).