DFT calculation on p-xylene sensing mechanism of (C 4 H 9 NH 3 ) 2 PbI 4 single crystal based on physisorption

P-xylene (p-C 8 H 10 ) is extremely harmful and dangerous to human health due to high toxicity and strong carcinogenicity. Exploring sensitive material to effectively detect p-xylene is of importance. In this paper, perovskite single crystal (C 4 H 9 NH 3 ) 2 PbI 4 has been successfully synthesized via solution method. The obtained product was analyzed by single crystal X-ray diffraction. With the space group Pbca, orthorhombic (C 4 H 9 NH 3 ) 2 PbI 4 layered perovskite structure consists of an extended two-dimensional network of corner-sharing PbI 6 octahedron. Single layer perovskite sheets of distorted PbI 6 octahedron alternated with protonated n-butylammonium cation bilayers, which offers many advantages and provides the possibility of forming a gas sensor device based on the change of resistances. Density functional theory (DFT) simulations regarding the adsorption energy revealed that this organic–inorganic hybrid perovskite compound has excellent selectivity toward p-xylene compared with other gases including C 2 H 5 OH, C 6 H 6 , CH 2 Cl 2 , HCHO, CH 3 COCH 3 and C 7 H 8 . The calculation of electron density, density of states and electron density difference showed the sensing mechanism of p-C 8 H 10 is mainly derived from physical adsorption–desorption in view of electron transfer. Graphic abstract For organic–inorganic hybrid perovskite (C 4 H 9 NH 3 ) 2 PbI 4 , single layer perovskite sheets of distorted PbI 6 octahedron alternated with protonated n-butylammonium cation bilayers (a), which offers many advantages and provides the possibility of forming a gas sensor device based on the change of resistances. Electron density difference calculation shows that adsorption of p-xylene molecule has an obvious effect on the electron distribution of (C 4 H 9 NH 3 ) 2 PbI 4 , results in electrically polarization as a local manner (b).