According to the clean water crisis, purification of water resources is so imperative. Reverse osmosis is the best method for the purification of wastewater. In this article, a new diol and resulting poly(keto ether sulfone) was synthesized and characterized successively. Innovative nanocomposites were prepared with the novel poly(keto ether sulfone) and various nanomaterials including clay, graphene oxide, multi‐walled carbon nanotube, and sepiolite. Polydopamine (PDA) was used to modify the hydrophilic nature of the nanoparticles surface. Thin‐film nanocomposites as reverse osmosis membranes were made by depositing of polyamide on the mentioned nanocomposites and investigated for removing metal ions like Cu (II), Co (II), Cr (II), Hg (II), Ni (II), Zn (II), and Pb (II) from water. The efficiency of membranes constructing from pristine poly(keto ether sulfone) and different nanocomposites as supporting layer of thin‐film nanocomposite were compared. The prepared membrane based on PDA‐modified MWCNT showed the best performance results including pure water flux of 215 L.m−2.h−1 and rejection of 98% for Cr (II).