Sulfonated Triazine-Based Porous Organic Polymers for Excellent Proton Conductivity

Abstract

Proton-exchange membrane fuel cells (PEMFCs) are a highly promising green and environmentally friendly way to serve the sustainable development of human civilization. However, high-cost synthesis and pollution problems of perfluorinated sulfonic acid membranes are still not resolved. In this research, we designed and constructed porous organic polymers (POPs) with high porosity and excellent stability via the Friedel-Crafts acylation reaction using commercial products as building blocks and low-cost FeCl3 as a catalyst through a simple operation. POP-BP-1 was successfully synthesized using 1,4-bis(chloromethyl)benzene as a cross-linking agent and reactant. POP-BP-TPOT was prepared using 2,4,6-triphenoxy-1,3,5-triazine (TPOT) as a building unit into the skeleton of POP-BP1. Sulfonated POPs (S-POPs) were densely decorated with sulfonic acid groups by postsulfonation. POP-BP-TPOT with abundant triazine units and sulfonic acid groups showed high water uptake. The sulfonated triazine-based polymer showed excellent proton conductivity up to 10(-2) S cm(-1) at 95% relative humidity (RH) under 25 degrees C and low activation energy of 0.19 eV. Fuel-cell test was also demonstrated using the polymer. This research suggests that the construction of S-POPs opens a suitable method to design high proton-conducting materials.