Crystalline Porous Organic Polymer Bearing -SO₃H Functionality for High Proton Conductivity

Designing high-performing proton-conducting materials with in-built -SO₃H moieties in the crystalline organic framework is very challenging in the context of developing an efficient solid electrolyte for fuel cells. Herein, we report a simple chemical route for synthesizing crystalline microporous sulfonic acid-functionalized porous organic polymers (MPOPS-1) via extended condensation polymerization between two organic monomers (i.e., cyanuric chloride and 2,5-diaminosulfonic acid) under refluxing conditions. The crystal structure of this organic framework has been indexed from powder X-ray diffraction data, revealing a monoclinic phase with a unit cell volume of 1627 ų. The presence of in-built sulfonic acid groups in MPOPS-1 contributes significantly to the high proton conductivity of this porous organic polymer. The resulting MPOPS-1 displays proton conductivities of 1.49 × 10^-5 and 3.07 × 10^-2 S cm^-1 at 350 K temperature under anhydrous and humid conditions, respectively, outperforming many previously reported porous organic polymers.