l -serine-functionalized montmorillonite decorated with Au nanoparticles: A new highly efficient catalyst for the reduction of 4-nitrophenol

•Gold nanoparticles immobilized onto K10 clay functionalized with l-serine linkers.•Total reduction of 4-nitrophenol to 4-aminophenol within 1 minute of reaction.•Formation of 4–5 nm gold particles promoted by NaBH4 used in reduction reactions.•Highly stable and efficient catalysts during 10 cycles with negligible Au leaching.