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 [Co2(COO)4N4]
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 × 104 M–1), nitrofurantoin (NFZ, K
sv: 3.0 ×
104 M–1), and sulfamethazine (SMZ, K
sv: 3.3 × 104 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 (Cr2O7
2–: 73.35; CrO4
2–: 189; and MnO4
–: 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.