Exploiting a Multi-Responsive Oxadiazole Moiety in One Three-Dimensional Metal–Organic Framework for Remedies to Three Environmental Issues

Abstract

Multifunctional metal–organic frameworks (MOFs) rely on the properties of metal centers (nodes) and/or linkers (struts) for their diverse applications in the emerging field of research. Currently, there is a huge demand for MOF materials in the field of capture/fixation/sensing of air pollutants, harmful chemical effluents, and nuclear waste. However, it is a challenging task to utilize one MOF for providing remedies to all these issues. On the basis of our current research activities, we have identified that an oxadiazole moiety–a five-membered ring with two different heteroatoms (O and N)–in a carboxylate linker can be the key to generating such MOF materials for its (a) inherent polarizable nature and molecular docking ability and (b) photoluminescence properties. In this work, we report a 3D MOF {[Co2(oxdz)2(tpbn)(H2O)2]·4H2O} n (1), self-assembled at room temperature from a three-component reaction, with an oxadiazole moiety (where H2oxdz = 4,4′-(1,3,4-oxadiazole-2,5-diyl)dibenzoic acid and tpbn = N,N′,N,”N″’-tetrakis(2-pyridylmethyl)-1,4-diaminobutane). The inherent polarizable nature of the oxadiazole moiety in 1 has been efficiently exploited for (i) multimedia iodine capture and (ii) fixation of CO2 under solvent-free and ambient conditions. On the other hand, the luminescent nature of the framework is found to be an efficient, highly preferred turn-on sensor for the ultra-fast detection of ketones with a limit as low as parts-per-trillion (mesitylene oxide: 447 ppt; cycloheptanone: 4.7 ppb; cyclohexanone: 17.2 ppb; acetylacetone: 18 ppb).

Ratiometric Fluorescence Thermometry, Quantitative Gossypol Detection, and CO2 Chemical Fixation by a Multipurpose Europium (III) Metal–Organic Framework

“…However, when the binary catalysts composed of the Eu-MOF catalyst and TBAB cocatalyst were used simultaneously, the conversion yield of propylene carbonate improved greatly (entries 4, 6, 7, Table ). The superior catalysis condition and the high conversion of the CO 2 conversion into cyclic carbonates for the Eu-MOF are comparable to those of the most reported MOFs with Lewis acid catalytic sites (Table S7 in the Supporting Information). − The attractive catalytic performance of the Eu-MOF can be ascribed to the exposed active sites of the skeleton such as unsaturated Eu 3+ ions and the uncoordinated nitrogen atoms of the H 3 TATAB ligands and suitable pore sizes of Eu-MOF that facilitate the diffusion of reactants and products. The catalytic mechanism for the cycloaddition reaction catalyzed by the Eu-MOF is similar with most previously reported MOFs, − and the possible mechanism of the conversion of CO 2 into the cyclic carbonates is illustrated in Figure S20 in the Supporting Information.…”

Mechanistic insight into a Co-based metal–organic framework as an efficient oxygen electrocatalyst via an in situ FT-IR study

“…The determination of the binding modes of the tetracarboxylate was done by analyzing the Fourier-transform infrared (FTIR) spectrum of Co-MOF and Co-MOF/G materials (Fig. S5†), and a detailed explanation is given in the ESI † 38 . Further, Raman spectroscopic analysis of Co-MOF/G and exfoliated graphene (EG) was accomplished to confirm the stacking of the Co-MOF materials in between graphene sheets, as shown in Fig.…”

“…S5 †), and a detailed explanation is given in the ESI. † 38 Further, Raman spectroscopic analysis of Co-MOF/G and exfoliated graphene (EG) was accomplished to conrm the stacking of the Co-MOF materials in between graphene sheets, as shown in Fig. S6.…”

pH-Stable Zn(II) Coordination Polymer as a Multiresponsive Turn-On and Turn-Off Fluorescent Sensor for Aqueous Medium Detection of Al(III) and Cr(VI) Oxo-Anions

“…In this context, coordination polymers (CPs) and/or metal–organic frameworks (MOFs) are attracting immense interest due to their intriguing properties, such as an accessible high surface area, ordered crystalline structure, permanent porosity, functional tunability, structural diversity, unique flexibility, and variable morphologies. − In particular, owing to the presence of well-organized chromophores (Lewis acid and basic sites) in their chemically tailorable framework, CPs/MOFs exhibit excellent luminescent properties. ,, Such superior properties make them fascinating as an effective sensing probe for the detection of variable analytes including toxic metal ions, hazardous anions, explosives, antibiotics, pesticides, and small organic molecules. ,,− Moreover, the specific host–guest interactions between the incoming analytes and the accessible functional groups of the framework bring more advantages in terms of easy operability, fast responsivity, high selectivity, good sensitivity, and multiple recyclabilities . − Taking advantage of such superiorities, although a large number of CPs/MOFs have been explored for the rapid detection of toxic metal cations and noxious oxo-anions individually or combinedly having turn-off luminescence only, ,,,, multiresponsive behavior with one turn-off and another turn-on luminescent detection by a single CP/MOF platform remains unexplored so far. Compared to single-analyte recognition, frameworks showing simultaneous and rapid sensing for multiple analytes are highly desirable and on-demand as they can increase the versatility and multipurpose usage possibility of the developed sensory materials. ,− On the other hand, although a decent number of coordination frameworks have displayed excellent luminescent performance with high sensitivity and selectivity, their insufficient hydrolytic stability, as well as chemical instability, , forced them to detect targeted analytes in a nonaqueous medium. , However, to make the developed framework affordable and easy to handle, it is desirable to develop robust sensor materials that ca...…”