Nanosponge membrane with 3D-macrocycle β-cyclodextrin as molecular cage to simultaneously enhance antifouling properties and efficient separation of dye/oil mixtures

Developing multifunctional, efficient and durable membrane for treating complex oily wastewater is highly desirable but still a challenge due to the severe membrane fouling. Herein, nanosponge membrane with 3D-macrocycle β-cyclodextrin (β-CDs) as molecular cage was manufactured by azide-alkyne click reaction for oil/water treatment and antifouling properties simultaneously. The macrocyclic ‘molecular cage’ geometry of β-CDs can induce various guest molecules into their cavities. When clickable β-CD-N3 was fixed onto a clickable EVAL-≡ membrane surface, the hydrophilicity of the membrane was greatly improved. Furthermore, the molecular cage–grafted membrane (EVAL-g-CD) showed better antifouling performance than a pure EVAL membrane, with lower water flux decline (15%) and higher water flux recovery (91%). The flux and separation efficiency values of the EVAL-g-CD membrane were higher than 120 L·m−2·h−1 and 99%, respectively. The EVAL-g-CD membrane also exhibited good adsorption performance for organic pollutants owing to its cavity structure. Furthermore, the membrane showed desirable stability and its rejection remained at 99% after filtration. This proposed 3D membrane strategy based on molecular cages sheds light on the formation of hydrophilic membrane surfaces and shows great promise for potential applications such as the separation of oil-in-water emulsions.