Electron Transfer Facilitated by π–π Stacking during the Nitrobenzene Recognition Process of an MOF Sensor
Bingqing Sun, Tingyu Tao, Lei Liu, Ran Ding, Yueyuan Mao
Abstract
Nitro-explosive sensors based on metal–organic frameworks (MOFs) are gaining increasing attention in the past few years. The detection mechanism is simply attributed to the electron transfer between the MOF sensor and the analyte, which is vague and lacks detailed information. By using density functional theory (DFT) and time-dependent DFT, this contribution uncovered the nitro-explosive detection mechanism of a typical MOF sensor at the molecular level. Both the periodic model and cluster model of the MOF sensor are applied to address this issue. The photo-induced electron transfer process is observed from the MOF sensor to nitrobenzene via two pathways. In the first pathway, electrons are directly excited from the valence band of the sensor to the unoccupied orbitals of nitrobenzene. In the second pathway, the electrons first flow from the valence band to the conduction band and then to the unoccupied orbitals of nitrobenzene. π–π stacking is a fundamental weak interaction and is observed between the analyte and the sensor. The presence of such interaction is proved to facilitate the electron transfer process, which plays a key role during the detecting process.