Devising Chemically Robust and Cationic Ni(II)–MOF with Nitrogen-Rich Micropores for Moisture-Tolerant CO₂ Capture: Highly Regenerative and Ultrafast Colorimetric Sensor for TNP and Multiple Oxo–Anions in Water with Theoretical Revelation

Abstract

Metal–organic frameworks (MOFs) show distinctive superiority for carbon dioxide (CO2) capture and luminescent sensing of toxic pollutants over other materials, where combination of both of these properties together with improvement of hydrolytic stability and pore functionality is critical to environmental remediation applications. The Ni­(II) framework [Ni2(μ2-OH)­(azdc)­(tpim)]­(NO3)·6DMA·6MeOH (CSMCRI-3) (tpim = 4,4′,4″-(1H-imidazole-2,4,5-triyl)­tripyridine, H2 azdc = azobenzene-4,4′-dicarboxylic acid, DMA = dimethylacetamide, CSMCRI = Central Salt & Marine Chemicals Research Institute), encompassing cationic [Ni2(μ2-OH)­(CO2)2] SBUs, is solvothermally synthesized from nitrogen-rich and highly fluorescent organic struts. The noninterpenetrated structure, containing free nitrogen atom affixed microporous channels, is stable in diverse organic solvents and weakly basic and acidic aqueous solutions. The activated MOF (3a) exhibits strong CO2-framework interaction and extremely selective CO2 adsorption over N2 (292.5) and CH4 (11.7). Importantly, water vapor exposure does not affect the surface area and/or multiple CO2 uptake-release cycles, signifying potential of the porous structure for long-term use under humid conditions. Aqueous-phase sensing studies illustrate extremely specific and ultrafast detection of explosive 2,4,6-trinitrophenol (TNP) via remarkable fluorescence quenching (K SV = 1.3 × 105 M–1), with a 0.25 ppm limit of detection (LOD). Furthermore, 3a serves as unique luminescent probe for highly discriminative and quick responsive detection of three noxious oxo–anions (Cr2O7 2–, CrO4 2–, MnO4 –) in water via noteworthy turn-off responses and extreme low LODs (Cr2O7 2– 0.9; CrO4 2– 0.29; MnO4 – 0.25 ppm). It is imperative to stress the outstanding reusability of the MOF toward multicyclic sensing of all four major water contaminants, alongside visible colorimetric changes upon individual analyte detection. Mechanistic insights in light of the electron transfer route together with density functional theory calculations portray the influence of pore functionalization in framework–analyte interactions, including alternation in energy levels, where varying degrees of contribution of energy transfer explicitly authenticates high quenching of the material.

A self‐penetrating and chemically stable zinc (ii)‐organic framework as multi‐responsive chemo‐sensor to detect pesticide and antibiotics in water

“…One thing to note is the fast‐growing metal organic frameworks (MOFs), which are designed from the perspective of molecules, making full use of the high stability of metal units and versatility of organic linkers, have attracted more and more attention for their potential applications in the fields of adsorption and separation, [ 4–10 ] electrode and photoelectric materials, [ 11–17 ] sensing and detection, [ 18–31 ] catalysis and photocatalysis. [ 32–34 ] Compared with other sensors, such as the conjugated organic probes, nanomaterials, carbon dots, oligomers, the luminescent metal–organic frameworks (LMOFs) possess obvious advantages of enormous structural diversity, adjustable pore size, large surface areas, readily function groups assisted analyte binding, and purposefully implanted active sites, render those LMOFs with the greatest potential as the sensory materials in detecting the POPs.…”

Applications of MOFs as Luminescent Sensors for Environmental Pollutants

“…[133] Up to now, various NACs categories of nitrobenzene (NB), methyl nitrobenzene (NT), nitrophenol (NP) have been detected, especially well-known TNP (Table 1). [134][135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153] In 2009, Li group firstly reported a luminescent [Zn 2 (bpdc) 2 (bpee)] for explosives sensing, offering a new application of microporous MOFs. [41] Inspired by this work, they further built another microporous LMOF of [Zn 2 (oba) 2 (bpy)]• 3DMA.…”

Mechanistic Insight into Charge and Energy Transfers of Luminescent Metal–Organic Frameworks Based Sensors for Toxic Chemicals

“…Overlapping of the TNP absorption band with the MOF emission band (Figure 7b) provided mechanistic information, showing that PET was insufficient to explain the whole mechanism, with RET also playing an important role in sensing. [244] The MOFs possessing H-bonding showed better electronic transitions and geometric stabilities that could be responsible for their enhanced sensing properties. [245] Similarly, intermolecular H-bonding interactions (O-H•••O and C-H•••O) were observed between the host 1,4-dioxane,4,4′-sulfonyldibenzoate, and 1,3,5-tris(imidazol-1-ylmethyl)-linked MOFs (Co(II)-MOF and Cd(II)-MOF) and guest TNP molecules.…”

“…b) Application of Ni(II)-MOF: HOMO-LUMO energies for linker tpim with nitro analytes; MOF HOMO-LUMO energy levels; TNP; redistribution energy gaps for the linker in the presence of TNP; geometry optimizations of tpim with TNP; and spectral overlap between the absorption and emission spectra (analyte and MOF, respectively). Reproduced with permission [244]. Copyright 2019, American Chemical Society.…”