I am trying to use ZnO nanoparticles(ZnO NPs) as catalyst for Coumarin synthesis. I tried Knoevenagel condensation under thermal conditions. I went with the literature and added salicylaldehyde, diethylmalonate and ZnO NPs but I am not getting any solid product. From what I know about Knoevenagel condensation, it requires a mild base which can abstract the acidic proton from diethylmalonate. Could lack of mild base be the reason for not getting any product?