A New 3D 10-Connected Cd(II) Based MOF With Mixed Ligands: A Dual Photoluminescent Sensor for Nitroaroamatics and Ferric Ion.

Jun Wang,Hongjia Xu,Lu Lu,Manoj Trivedi,Jian Wu,Abhinav Kumar,Jianqiang Liu,Mingbin Zheng

doi:10.3389/fchem.2019.00244

Abstract

The precise unification of functional groups and photoluminescence properties can give rise to MOFs that can offer diverse applications like selective detection of nitroaromatic compounds (NACs) which are considered to be an important ingredient of explosive as well as cation and anion sensing. Hence, a new 3D metal-organic framework (MOF) [Cd2(btc)(bib)(HCOO)(H2O)·H2O]n (1) has been synthesized using mixed ligand strategy by solvothermal reaction of cadmium acetate with two ligands viz. 1,3,5-benzenetricarboxylic acid (H3btc) and 1,4-bis(2-methyl-imidazol-1-yl)butane (bib). The MOF 1 possesses highly 10-connected network which is based on {Cd4(btc)2(bib)4} molecular building block. The studies showed that 1 could be taken as the fluorescent sensor for sensitive recognition of NACs, in particular 2,4,6-trinitrophenol (TNP) with notable quenching (Ksv = 5.42 × 104 M−1) and LOD of 1.77 ppm. Additionally, 1 also displayed selective sensing for Fe3+ ions with Ksv = 6.05 × 103 M− 1 and LOD = 1.56 ppm. Also, this dual sensor displayed excellent reusability toward the detection of TNP and Fe3+ ion. Theoretical calculations have been performed to propose the probable mechanism for the sensing luminescence intensity. Calculations indicated that because of the charge transfer and weak interaction that is operating between NACs and MOF, the weakening in the photoluminescence intensity resulted.

Highlights

The single-crystal X-ray diffraction results indicate that 1 crystallizes in triclinic space group P-1. 1 is a 3D architecture having binuclear Cd(II) clusters as secondary building units(SBUs) which in turn is constructed by mixed ligands viz. btc and bib. 1 shows two types of Cd(II) centers with different coordination fashions
The four Cd(II)centers are divulged by two bridged formates and two carboxylates of btc. Further it spreads out with six 3-connected btc and four linear imidazole-based bib ligands and in this way, this tetra-cadmium SBU can be simplified into a 10-connected node
The evacuated 1 shows theoretical porosity of 15.8% according to PLATON calculations with a probe radius of 1.65 Å (Spek, 2003)

Summary

Introduction

Tremendous amount of efforts have been devoted in developing new metal-organic frameworks (MOFs) which display photoluminescent properties and this class of luminescence materials can be in demand for solving the pollution problems and can offer potential application as luminescent sensors (Hua et al, 2015; Li et al, 2015; Shi et al, 2015; Wang et al, 2015, 2017; Liu et al, 2016a,b, 2017; Chen et al, 2017; Lu et al, 2017; Ma et al, 2017). Numerous luminescent MOFs have been documented which had been utilized to detect metal ions and small organic compounds (Cui et al, 2012). The possible mechanism associated with the sensing properties of these materials depend on monitoring of the transmission signals generated during interactions that are taking place between sensors (guest) and substrates (host) (Gole et al, 2011; Pramanik et al, 2011; Chen et al, 2013; Balamurugan et al, 2014)

Methods

Results

Conclusion