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-O_Br and PPyTri-O_Cl 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-O_Br and PPyTri-O_Cl, 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.