Selective oxidation of 5-hydroxymethylfurfual (HMF) to 2,5-furandicarboxylic acid (FDCA) as a bioplastics monomer is efficiently promoted by a simple system without noble-metal and base additives.In this work,graphene oxide (GO) was first synthesised by an electrochemical method with flexible graphite paper (FGP) as start carbon material,then,nitrogen-doped graphene (NG) layers encapsulated Cu nanoparticles (NPs) was prepared by one-step thermal treatment of GO supported Cu2+ in flowing NH3 atmosphere.Compared with NG supported Cu NPs prepared by the traditional impregnation method,enhanced catalytic activity was achieved over Cu/NG and an FDCA yield of 95.2％ was achieved under mild reaction conditions with tert-butylhydroperoxide (t-BuOOH) as the oxidant.Control experiments with different catalysts and different addition procedure of t-BuOOH showed the yield of HMF and various intermediates during reaction.From the changing of intermediates concentrations and reaction rates,a reaction pathway through HMF-DFF-FFCA-FDCA was proposed.This work gives a more convenient,more green,more economical and effective method in encapsulated metal NPs preparation and high selectivity in HMF oxidation to FDCA under mild conditions.