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The detection of toxic molecules has gained imperial attention to protect living organisms and their environment. The broadly explored sensor behaviour of triazine-based C3N4 reveals their ultra-high sensitivity towards numerous toxic molecules e.g., chemical welfare agents. However, another potential analogue of C3N4 composed of heptazine exhibits remarkable electrical and optical properties but has not been much explored in sensor technology, especially for toxic pollutants. Keeping this in mind, the sensing performance of heptazine-based g-C3N4 is explored for the detection of toxic amides by using First Principles calculations. In this context, acryloyl amide (C2H3CONH2), acryloyl chloride (C2H3COCl), fluoroacetic acid (C2H3FCOOH), flouroaceta amide (C2H2FONH2), flouroacetyl chloride (C2H2FOCl) are selected as toxic pollutants; herein, for the ease of understanding, these molecules are represented as AAM, ACl, FAAc, FAA, & FACl, respectively. The electrochemical sensitivity of g-C3N4 is determined via geometric, energetic, and electronic properties analysis, whereas the photochemical sensitivity is explored by UV–Vis absorption analysis based on TD-DFT calculations. The interaction energies of studied molecules on C3N4 range between − 9.09 and - 23.39 kcal/mol depending upon the type of interactions e.g., hydrogen bonding or dispersion, which are explained on the basis of Symmetry Adopted Perturbation Theory, Non-Covalent Interaction Index, and Quantum Theory of Atoms in Molecules analyses. The density of State analysis, Frontier Molecular Orbitals and NBO charge transfer characterized that the electronic behaviour of g-C3N4 can be an effective sensor material with a semiconducting nature and significant charge transfer. Lastly, UV–Vis absorption analysis confirms the photosensitivity of g-C3N4 upon interaction with toxic molecules. [ABSTRACT FROM AUTHOR]

Ab initio calculations were performed to determine the sensing behavior of g-C 3 N 4 and Li metal-doped g-C 3 N 4 (Li/g-C 3 N 4 ) quantum dots toward toxic compounds acetamide (AA), benzamide (BA), and their thio-analogues, namely, thioacetamide (TAA) and thiobenzamide (TAA). For optimization and interaction energies, the ωB97XD/6-31G(d,p) level of theory was used. Interaction energies ( E int ) illustrate the high thermodynamic stabilities of the designed complexes due to the presence of the noncovalent interactions. The presence of electrostatic forces in some complexes is also observed. The observed trend of E int in g-C 3 N 4 complexes was BA > TAA > AA > TBA, while in Li/g-C 3 N 4 , the trend was BA > AA > TBA > TAA. The electronic properties were studied by frontier molecular orbital (FMO) and natural bond orbital analyses. According to FMO, lithium metal doping greatly enhanced the conductivity of the complexes by generating new HOMOs near the Fermi level. A significant amount of charge transfer was also observed in complexes, reflecting the increase in charge conductivity. NCI and QTAIM analyses evidenced the presence of significant noncovalent dispersion and electrostatic forces in Li/g-C 3 N 4 and respective complexes. Charge decomposition analysis gave an idea of the transfer of charge density between quantum dots and analytes. Finally, TD-DFT explained the optical behavior of the reported complexes. The findings of this study suggested that both bare g-C 3 N 4 and Li/g-C 3 N 4 can effectively be used as atmospheric sensors having excellent adsorbing properties toward toxic analytes., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)