The tripartite role of 2D covalent organic frameworks in graphene-based organic solvent nanofiltration membranes

Two-dimensional covalent organic frameworks (2D-COFs) have welldefined porosity and stability. Herein, we demonstrate that 2DCOFs can have three roles in nanolaminated graphene membranes for organic solvent nanofiltration (OSN). The optimized hybrid nano laminate, assembled from 2D-COFs and reduced graphene oxide (rGO), shows a 162% enhancement in methanol permeance without sacrificing selectivity. When dry, intercalated 2D-COFs serve as a nanospacer to prevent the restacking of rGO. However, when wetted, 2D-COFs assume the additional roles of a stabilizer and a porous filler material. 2D-COFs alleviate rGO swelling in solvents because of a solvation-driven charge redistribution at the COF/ rGO interface, which induces an attractive stabilizing force between COF and rGO nanosheets. Further, 2D-COFs can reduce transport pathway length by 15.5% and deliver shortcutsfor solvent permeance. This work unravels the tripartite role of 2D-COFs as nanospacers/stabilizers/porous fillers, offering new insights into shaping the development of hybrid nanolaminated membranes for OSN.

Automated summary

The study demonstrates the tripartite role of two-dimensional covalent organic frameworks (2D-COFs) in nanolaminated graphene membranes, acting as nanospacers, stabilizers, and porous filler materials. This new insight offers potential for shaping the development of hybrid nanolaminated membranes for organic solvent nanofiltration.