Interpenetrated Robust Metal–Organic Framework with Urea-Functionality-Decked Pores for Selective and Ultrasensitive Detection of Antibiotics and Oxo-anions
Partha Pratim Mondal, D. Muthukumar, Shifna K. P. Fathima, Renjith S. Pillai, Subhadip Neogi
Abstract
Conjoining the benefits of structural diversity and deliberate implantation of task-specific sites inside the porous channels, metal–organic frameworks (MOFs) not only ensure environmental remediation via acute detection of organic as well as inorganic pollutants but also rationalize structure–performance synergies to devise smarter materials with advanced performances. Herein, we report a urea-functionality-grafted Co(II)-framework (UMOF) based on a mixed ligand approach. The 3-fold interpenetrated and [Co 2 (COO) 4 N 4 ] building unit-containing structure exhibits high stability and free-carboxamide-site-decorated microporous channels. Assimilation of high-density hydrogen-bond donor groups plus the π-electron-rich aromatic ligand benefits the UMOF acting as a selective fluoro-sensor for three noxious antibiotics through remarkable quenching, including nitrofurazone (NFT, K sv: 3.2 × 10 4 M –1 ), nitrofurantoin (NFZ, K sv: 3.0 × 10 4 M –1 ), and sulfamethazine (SMZ, K sv: 3.3 × 10 4 M –1 ) with ppb level limits of detection (LODs, NFT: 110.42, NFZ: 97.89, and SMZ: 78.77). The mechanistic insight of luminescence quenching is supported from density functional theory calculations, which endorse the electron-transfer route via portraying variation in the energy levels of the urea group-affixed linker by individual organo-toxins, besides verifying analyte–linker noncovalent interactions. The framework further demonstrates highly discriminative turn-off detection of oxo-anions with extreme low LODs (Cr 2 O 7 2–: 73.35; CrO 4 2–: 189; and MnO 4 –: 49.96 ppb). Of note is the reusability of the UMOF toward multicyclic sensing of all the organic and inorganic analytes besides their fast-responsive detection, where variable magnitudes of energy-transfer contributions unequivocally authenticate the turn-off event.