Room temperature sensing of CO2 using C3-symmetry pyridinium-based porous ionic polymers with triazine or benzene cores

A new class of ionic polymers tethering triazine (benzene) core hybrids with three dipyridinium as cationic counterparts combined with bromide and/or chloride anions PPyBz-OBr and PPyTri-OCl were successfully prepared via the alkylation of 4,4 '-dipyridyl derivatives 4,4 '-bp-O with 1,3,5-tris(bromomethyl)benzene BB and/or cyanuric chloride CC. The precursor, 4,4 '-bp-O,was synthesized through the condensation of 4-pyridine carboxaldehyde and 4,4 '-oxydianiline. The resulting ionic polymers, PPyBz-OBr and PPyTri-OCl, underwent metathetical anion exchange, forming new ionic polymers bearing LiTFSI and KPF6 as anions. Characterization of the synthesized hybrid molecules was performed through FTIR, 1H NMR, and 13C NMR analyses. PXRD and SEM showed semi-crystalline structures and a homogenous distribution of micro-/or nanoparticles. TGA and DTA displayed high thermal stability of the synthesized polymer. The sensing activity of the modified ionic polymers was examined using a quartz crystal nanobalance (QCN) for CO2 detection. The resulting sensor demonstrated the ability to provide precise, selective, and reproducible CO2 measurements.