Quantum chemical analysis of porphyrin-based sensors: Adsorption and sensing capabilities of pure, protonated, and metallic porphyrins insights into volatile organic compounds (VOCs)

Precise monitoring and detection of pollutants is crucial because of the significant challenges posed by volatile organic compounds (VOCs), as they can severely impact the human health and environment. Our work presents a comprehensive investigation into the sensing capabilities of porphyrin-based materials, specifically focusing on 5,10,15,20-tetrakis-(4-aminophenyl) porphyrin (TAPP), its protonated form, and zinc-substituted TAPP (ZnTAPP). Utilizing first-principles density functional theory (DFT) methods, we explore the interactions between these porphyrins and a range of volatile organic compounds (VOCs). Our findings reveal that pure TAPP exhibits a strong adsorption affinity for triethylamine (TEA), while both protonated TAPP and Zn-TAPP demonstrate enhanced adsorption to ammonia. However, pure and protonated TAPP are sensitive and selective towards TEA, in contrast, Zn-TAPP exhibits enhanced sensitivity and selectivity towards ammonia, a significant air pollutant. The study highlights the critical role of electronic properties, such as HOMO-LUMO gaps and dipole moments, in determining the reactivity and stability of these porphyrins. Additionally, we employ visual studies, including quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses, to elucidate the nature of molecular interactions. Our results not only validate previous experimental findings but also pave the way for the development of highly sensitive and selective chemi-resistive sensors for environmental monitoring applications.