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• Catalysts for the Knoevenagel are synthesized from different carbon sources such as melamine, dicyandiamide, chitosan, etc. • Co-N-C synthesized with melamine as a carbon source gave yields as high as 93.7% with excellent stability and recyclability. • Promotion of the Knoevenagel reaction by a solid frustrated Lewis pair (FLP) consisting of Coδ+ and Nδ- is discussed. Nitrogen-doped carbon confined cobalt nanoparticles (Co-N-C) were synthesized through multi-step pyrolysis method. The Co-N-C samples exhibit excellent catalytic performance in the Knoevenagel reaction of benzaldehyde and malononitrile, of which the yield can be as high as 93.7% within 2.5 min with outstanding stability and recyclability. The catalytic performance may be primarily ascribed to the richness in nitrogen and cobalt in the form of the solid Frustrated Lewis Pair (FLP), i.e. the Co ion acts as a Lewis acid site to activate the carbonyl oxygen of benzaldehyde molecules, and nitrogen in carbon acts as a Lewis base site to activate the methylene hydrogen of malononitrile. From the perspective of intrinsic catalytic activity, variations in catalytic properties are attributed to the electron density distribution on the surface of the catalyst. Nitrogen-doped carbon confined cobalt nanoparticles as the acid-base bifunctional catalysts exhibit excellent catalytic performance for the Knoevenagel reaction between benzaldehyde and malononitrile, which may be primarily ascribed to the highest contents of nitrogen and Cobalt in the form of the solid Frustrated Lewis Pair (FLP) from Coδ+ of Co nanoparticles and Nδ− of nitrogen-contained species. [Display omitted] [ABSTRACT FROM AUTHOR]