Boosting the adsorption capacity/selectivity of graphene oxide membranes via photocatalytic perforation for water treatment

Designing a porous morphology with surface functionality and reactivity is one of the persistent challenges to realising the potential of nanoporous graphene in energy-efficient membranes. Herein, the authors developed precisely tuned adsorption membranes derived from graphene with well-defined capacity ranges and removal kinetics for several organic molecules as representative effluents discarded in wastewater. A photocatalytic etching procedure was employed to perforate ultrathin graphene oxide, generating a variety of in-plane nanopores with diameters ranging from 20 - 100 nm and a maximum surface density of 10 3 pores/μm 2 based on the perforation conditions. Fine-tuning the perforation conditions enables the model’s effluent surface adsorption capacity of perforated membranes to be precisely engineered. This surface modification achieved the highest dye adsorption capacity of 800 mg/g for cationic organic molecules (e.g., methylene blue), which was 4 times greater than that of analogous pristine materials. These membranes also showed preferential selectivity for cationic/ionic molecules, achieving 40% greater selectivity than pristine membranes. Molecular dynamics simulations considered the mobility of the dyes at the atomic level and suggest that methylene blue can diffuse faster through the pores into the graphitic sheets, than the Evans blue dye molecules. These findings supported experimental trends, enabling comparisons based on dye mobility and revealing the interactions between functional groups of dye molecules and the chemistry of nanoporous graphene membranes. • Perforation-generated graphene with tunable nanopores. • Adsorption capacity tuned by etching, reaching up to 800 mg/g for dyes • Cationic dye selectivity enhanced by 40% compared to pristine graphene. • Molecular dynamics revealed faster methylene blue diffusion through pores • Surface chemistry and pore structure governed dye–membrane interactions