A graphene-based porous composite hydrogel for efficient heavy metal ions removal from wastewater

•A robust and adsorbable GO-g-P4VP@PAA composite hydrogel was fabricated.•The P4VP brushes tethered on GO surface significantly improve the compatibility with PAA matrix.•The hydrogel with a special interconnected 3D porous network exhibits good compressive strength.•The hydrogel has comparatively high adsorption capacity for Pb2+ and Cd2+.•The supramolecular hydrogel possesses fast adsorption rate, good reusability, and convenient use.