Sensing mechanism elucidation of a chemosensor based on a metal‐organic framework selective to explosive aromatic compounds

Abstract

Theoretical elucidation of the turn-off mechanism of the luminescence of a chemosensor based on a metal-organic framework (MOF) [Zn 2 (OBA) 4 (BYP) 2 ] (BYP: 4,4 0bipyridine; H 2 OBA: 4,4 0-oxybis[benzoic acid]), selective to nitrobenzene (NB) via quantum chemical computations, is presented. The electronic structure and optical properties of Zn-MOF were investigated through the combination of density functional theory (DFT) and time-dependent DFT methods. Our results indicate that the fluorescence emission is governed by a linker (BPY)-to-linker (OBA) charge transfer (LLCT) involving orbitals π-type. Next, the interaction with the analyte was analyzed, where very interesting results were obtained, that is, the lowest unoccupied molecular orbital is now composed of orbitals from NB, which changes the emissive state of the Zn-MOF. This suggests that the LLCT process is blocked, inducing the fluorescence quenching. Otherwise, the Morokuma-Ziegler energy decomposition and natural orbitals for chemical valence on the Zn-MOF-NB interactions were studied in detail, which illustrate the possible channels of charge transfer between Zn-MOF and NB. Finally, we believe that this proposed methodology can be applied to different chemosensor-analyte systems to evidence the molecular and electronic factors that govern the sensing mechanisms.

Electron Transfer Facilitated by π–π Stacking during the Nitrobenzene Recognition Process of an MOF Sensor

“…As periodic structures of the MOF sensor are usually characterized by localized electronic states, truncated clusters are usually used to investigate the photo-physical processes of MOFs, which agree well with experimental data. [30][31][32]36,37 Besides, periodic plane wave method is not good at investigating the photo-excitation process, cluster models truncated from the periodic models are used in the below sections. As is shown in Figure 4, four cluster structures are obtained to represent the MOF sensor, MOF−Ac, MOF−Ben, and MOF−NB.…”

“…16−18 In 2020, Hidalgo-Rosa and co-workers performed a series of insightful investigations on the luminescence sensing mechanism of MOF-based sensors. 36,37 By exploring the sensing mechanism for aniline 36 and nitrobenzene, 37 the effects of hydrogen bonding interactions are clarified. In the case of MOF sensor, π−π stacking and hydrogen bonding may be present or coexist between the analyte and the sensor and play important roles during the sensing process.…”

“…It is reported to facilitate electron transfer during the photo-excitation process of the DNA and G-quadruplex, which is responsible for photo-induced damages. − Recently, Han and co-workers investigate the TNT detection mechanism of two pyrene-based sensors. , π–π stacking, in both cases, is found to exist between the sensor and the analyte, which plays a key role during the detecting process. The hydrogen bonding interaction also plays crucial roles in the photo-physical process of organic dyes and sensors. − In 2020, Hidalgo-Rosa and co-workers performed a series of insightful investigations on the luminescence sensing mechanism of MOF-based sensors. , By exploring the sensing mechanism for aniline and nitrobenzene, the effects of hydrogen bonding interactions are clarified. In the case of MOF sensor, π–π stacking and hydrogen bonding may be present or co-exist between the analyte and the sensor and play important roles during the sensing process. , However, the co-effects of the two interactions on the electron transfer process between the analyte and the sensor remains uncovered.…”

Understanding the Deactivating/Activating Mechanisms in Three Optical Chemosensors Based on Crown Ether with Na+/K+ Selectivity Using Quantum Chemical Tools

“…[13][14][15] These effects are determined by a series of transduction mechanisms [16,17] based on Energy Transfer (ET) [18][19][20][21] and Charge Transfer (CT). [20,[22][23][24] The most common transduction mechanisms are photoinduced electron transfer (PET), [8,25,26] intramolecular charge transfer (ICT), [27,28] twisted intramolecular charge transfer (TICT), [12,29] ground, or excitedstate intramolecular proton transfer (GSIPT or ESIPT), [8,[30][31][32] and metal-ligand or ligand-metal charge transfer (MLCT or LMCT). [33][34][35] These transduction mechanisms and selectivity are determined by the electronic and molecular structure of the sensors.…”

Insights into the selective sensing mechanism of a luminescent Cd(II)-based MOF chemosensor toward NACs: roles of the host–guest interactions and PET processes

“…This fact has led luminescent metal-organic frameworks (L-MOFs) as successful alternatives to develop chemosensors based on the luminescence changes upon recognition of the analytes [11,12]. Among these chemosensors, luminescent systems have currently encouraged researchers to focus on designing materials that show a remarkable response in their optical properties, induced by the host-guest interactions with a specific analyte (guest) [13,14]. L-MOFs have interesting structural features that are responsible of special luminescent properties, since light emission in L-MOFs generally arises from their building components: linkers (conjugated organic ligands) and/or nodes (metal ions or clusters).…”