In-situ grown covalent organic framework nanosheets on graphene for membrane-based dye/salt separation

Covalent organic framework-1 (COF-1) with ordered channel structure and precise pore size covalently attaching the surface of graphene oxide (GO) was synthesized by in-situ growth. The prepared GO/COF-1 nanocomposite improves dispersivity and stability in water over COF-1, allowing GO/COF-1 nanocomposite to be used as membrane material for water treatment. Here, high-flux membranes-based hybrid 2D-2D GO/COF-1 nanocomposites were constructed on the support of Polyacrylonitrile (PAN) ultrafiltration membrane using a dead-end filtration device. The prepared membranes exhibit an excellent water permeation over 310 L m-2 h−1 MPa−1, high rejection rate for water soluble dyes (>99%) and high permeability for ion salts. The outstanding dye rejection and water permeation performance can be attributed to the physical size sieving of COF-1 (the layer distance of near 0.33 nm) and the suitably interlayer spacing between the adjacent GO sheets. Moreover, electrostatic interaction also plays an important role for the rejection process. This approach presents an enormous potential for purification of dye wastewater.