Study on the properties of hybrid COF connected three-dimensional nanofiber structures in proton exchange membranes

Nanofibers have been widely used in the construction of proton exchange membranes(PEM), which can be used to modify Nafion membranes and enhance their mechanical properties. With the addition of nanofibers, some of the sulfonic acid active sites in the perfluorosulfonic acid matrix are occupied, and the conductivity decreases. A covalent organic framework (COF) can be used to compensate for this. In this paper, hybrid COFs modified with sulfonic and pyridine groups were selected and synthesized in situ on polyacrylonitrile (PAN) fibers, and the fibers were placed in a perfluorosulfonic acid matrix to form a sandwich shaped composite membrane. The hybrid COF generates a small fiber-like structure to connect the PAN fibers, which improves the connectivity between three-dimensional nanofibers. This structure also plays a role in enhancing longitudinal proton transport ability of the composite membrane, which provides a new idea in the study of PEM.