Validation of 'lock-and-key' mechanism of a metal-organic framework in selective sensing of triethylamine

Kowsalya Vellingiri; Danil W Boukhvalov; Ki-Hyun Kim; Ligy Philip

doi:10.1039/c8ra10637a

Validation of 'lock-and-key' mechanism of a metal-organic framework in selective sensing of triethylamine

RSC Adv. 2019 Mar 11;9(14):7818-7825. doi: 10.1039/c8ra10637a. eCollection 2019 Mar 6.

Authors

Kowsalya Vellingiri¹, Danil W Boukhvalov^{2

3}, Ki-Hyun Kim⁴, Ligy Philip¹

Affiliations

¹ Environmental and Water Resources Engineering Division, Department of Civil Engineering, IIT Madras Chennai 600 036 India ligy@iitm.ac.in.
² College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University Nanjing 210037 P. R. China.
³ Theoretical Physics and Applied Mathematics Department, Ural Federal University Mira Street 19 620002 Yekaterinburg Russia.
⁴ Department of Civil and Environmental Engineering, Hanyang University 222 Wangsimni-Ro Seoul 04763 Korea.

Abstract

To develop the metal-organic framework (MOF)-based sensing of triethylamine (TEA) in an aqueous phase, Al-MIL-101-NH₂ (MIL: Material Institute Lavoisier) with a tripod-like cavity was utilized based on a lock-and-key model. Al-MIL-101-NH₂ (Al-MOF) was found to be an excellent fluorescent sensor for the TEA molecules in the range of 0.05-0.99 mM. The limit of detection (LOD) and linear calibration range of this probe towards TEA were found to be 3 μM and 0.05-0.40 mM, respectively. The mechanism of the sensing process indicates the dominant role of physical processes (e.g., non-covalent bond interactions). In addition, the exact fit of the TEA molecule (6.5 Å) in the tripod-like cavity (6.78 Å) supported the strong interaction between three ethyl groups (TEA) and aromatic rings (MOF). This kind of specific suitability between size/shape of the TEA and tripod-like cavity of MOF (ΔG: -46.7 kJ mol^-1) was not found in other molecules such as ethylamine (ΔG: -2.20 kJ mol^-1 and size: 3.7 Å), formaldehyde (ΔG: +1.50 kJ mol^-1 and size: 2.8 Å), and ammonia (ΔG: +0.71 kJ mol^-1 and size: 1.6 Å). As such, Al-MOF was found to be a selective and stable sensor for TEA.