In-situ preparation of size-tunable gold nanoparticles in porous resorcinol–formaldehyde resin

•Au nanoparticles (NPs) with tunable size were prepared using porous resorcinol–formaldehyde resin (RF) as support.•Au NPs can be deposited on the RF particle surface or inside the RF particles by adjusting pH of the solutions.•Phenolic hydroxyl groups in RF support act as both ligand and reductant to promote formation of the Au NPs.•Au NPs loaded in RF with optimal size show balanced activity and stability in catalytic reaction.