Mechanoassisted Synthesis of Sulfonated Covalent Organic Frameworks with High Intrinsic Proton Conductivity

It
is challenging to introduce pendent sulfonic acid groups into modularly
built crystalline porous frameworks for intrinsic proton conduction.
Herein, we report the mechanoassisted synthesis of two sulfonated
covalent organic frameworks (COFs) possessing one-dimensional nanoporous
channels decorated with pendent sulfonic acid groups. These COFs exhibit
high intrinsic proton conductivity as high as 3.96 × 10–2 S cm–1 with long-term stability at ambient temperature
and 97% relative humidity (RH). In addition, they were blended with
nonconductive polyvinylidene fluoride (PVDF) affording a series of
mixed-matrix membranes (MMMs) with proton conductivity up to 1.58
× 10–2 S cm–1 and low activation
energy of 0.21 eV suggesting the Grotthuss mechanism for proton conduction.
Our study has demonstrated the high intrinsic proton conductivity
of COFs shedding lights on their wide applications in proton exchange
membranes.