New insights into the exploitation of oxidized carbon nitrides as heterogeneous base catalysts

In this work, the development of a novel efficient heterogeneous catalytic system capable of driving Knoevenagel condensation reactions between benzaldehydes and malononitrile was reported. Specifically, we explored a postsynthetic modification of graphitic carbon nitride (g-CN) through a strong oxidation treatment by acid mixture (HNO3/H2SO4). The as-prepared oxidized CN material (CNO) shows a large number of surface acidic moieties, that can be easily deprotonated through an aqueous alkaline wash with different bases (NaOH, K2CO3, t-BuOK), to introduce a high density of reactive basic sites. The best catalyst is obtained with NaOH as the base (CNONaOH), and displays high reactivity and good tolerance towards functional group variations of the reagents, thus emerging as a potential new recyclable carbon nitride-based structure for organic base catalysis.