π-Conjugated Porous Polymer Nanosheets for Explosive Sensing: Investigation on the Role of H-Bonding

Nitroaromatic explosive sensing plays a critical role in ensuring public security and environmental protection. Herein, we report 2-pyridyl-thiazolothiazole (pyTTz) integrated blue-fluorescent π-conjugated porous polymer nanosheets, NTzCMP and TzCMP for selective sensing of picric acid (PA) among nitrophenol explosives. Acid-base interactions between PA and pyTTz of CMP lead to H-bonding interactions, where the hydroxy group of PA engaged in weak H-bonding interactions with pyridine and TTz of pyTTz moiety. This led to a strong fluorescence quenching of CMPs-such formation of ground state complex was supported by linear Stern-Volmer quenching plots, unaltered excited state lifetimes, and detailed FTIR analysis of PA exposed CMPs. Interestingly, both CMPs exhibited an excellent response to smaller analytes such as o-nitrotoluene compared to 2,4-dinitrotoluene. Both NTzCMP and TzCMP CMPs exhibited high K_SV values of 9×10³ and 2.1×10³ M^-1 for PA and the corresponding limit of detection values were found to be 0.46 and 1.6 ppm, respectively.