Membranes assembled from nanomaterials are widely studied in separation field. Herein, a novel 0D/2D composite membrane was fabricated for water purification. The 0D nanomaterial is Fe(OH) 3 nanoparticles and the 2D nanomaterial is g-C3N4 nanosheets. For the Fe(OH)(3)/g-C3N4 composite membrane, the g-C3N4 layer acts as support for the deposition of Fe(OH)(3) nanoparticles, while the Fe(OH)(3) nanoparticles layer serves as separation layer. The Fe(OH)(3) nanoparticles bond with the g-C3N4 layer through electrostatic interaction. The composite membrane demonstrates a pure water permeance of 48 Lm(-2) h(-1) bar(-1) and has a molecular weight cut-off (MWCO) of 800 Da. The excellent separation performance is attributed to that the g-C3N4 layer shows little water transport resistance and pores formed between Fe(OH) 3 nanoparticles are uniform. Benefitting from the electrostatic interaction, the composite membrane demonstrates a good stability in aqueous environment during 40 h operation. In addition, the morphologies, surface hydrophilicity, separation performance and stability of the composite membrane were investigated in detail.