Impact of Zr6 Node in a Metal-Organic Framework for Adsorptive Removal of Antibiotics from Water

Preparation of Zn/Zr-MOFs by microwave-assisted ball milling and adsorption of lomefloxacin hydrochloride and levofloxacin hydrochloride in wastewater

The Zn/Zr-MOFs were synthesized via microwave-assisted ball milling and subsequently characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The thermal stability of the Zn/Zr-MOFs was evaluated through thermogravimetry (TGA). The results demonstrated the exceptional adsorption properties of the Zn/Zr-MOFs towards Lomefloxacin hydrochloride and Levofloxacin hydrochloride. At a concentration of 30 ppm for Lomefloxacin hydrochloride, the addition of 30 mg of Zn/Zr-MOFs material resulted in an adsorption capacity of 179.2 mg•g-1. Similarly, at a concentration of 40 ppm for Levofloxacin hydrochloride, the addition of 30 mg Zn/Zr-MOFs material led to an adsorption capacity of 187.1 mg•g-1. Kinetic analysis revealed that the experimental data aligned well with a pseudo-second order kinetic model. Overall, these findings highlight the significant potential application of Zn/Zr-MOF materials in wastewater treatment.

Visible-Light-Driven Z-Type Pg-C3N4/Nitrogen Doped Biochar/BiVO4 Photo-Catalysts for the Degradation of Norfloxacin

Antibiotics cannot be effectively removed by traditional wastewater treatment processes, and have become widespread pollutants in various environments. In this study, a Z-type heterojunction photo-catalyst Pg-C3N4 (PCN)/Nitrogen doped biochar (N-Biochar)/BiVO4 (NCBN) for the degradation of norfloxacin (NOR) was prepared by the hydrothermal method. The specific surface area of the NCBN (42.88 m2/g) was further improved compared to BiVO4 (4.528 m2/g). The photo-catalytic performance of the catalyst was investigated, and the N-Biochar acted as a charge transfer channel to promote carrier separation and form Z-type heterojunctions. Moreover, the NCBN exhibited excellent performance (92.5%) in removing NOR, which maintained 70% degradation after four cycles. The main active substance of the NCBN was •O2-, and the possible degradation pathways are provided. This work will provide a theoretical basis for the construction of heterojunction photo-catalysts.

A Zn(II) coordination polymer as a dual sensor for ppb level detection of antibiotics and organo-toxins in a green solvent

Herein, we describe the synthesis of a new fluorescent d¹⁰ coordination polymer, [Zn₂(CFDA)₂(BPEP)]_n·nDMF (CP-1) under solvothermal reaction condition using zinc metal ion. In CP-1, Zn(II) ion along with CFDA and BPED ligand forms a 2-fold self-interpenetrated 3D coordination polymers. This CP-1 is characterized by the single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), infrared spectra, optical microscope image and thermogravimetric analysis and the framework is found to maintain its structural stability in different solvents. The framework (CP-1) detected antibiotics (NFT (nitrofurantoin) and NZF (nitrofurazone)) and organo-toxin trinitrophenol in aqueous dispersed medium. Apart from the fast responsive (10 s), the detection limit for them was found at ppb level. The detection of these organo-aromatics were also comprehended by the colorimetric response through solid, solution and low cost paper strip technique i.e., triple mode recognition capability. The probe is re-usable without changing in its sensing efficiency and in addition, it has been applied for the detection of these analytes in the real field specimens (soil, river water, human urine and commercial tablet). The sensing ability is established by in-depth experimental analysis and the life time measurement where mechanism such as photo induced electron transfer (PET), fluorescence resonance energy transfer (FRET), inner filter effect (IFE) was recognized. The presence of guest interaction sites on the linker backbone in CP-1 induces diverse supramolecular interaction with the targeted analytes results to bring them in proximity for the occurrence of these sensing mechanism. The Stern-Volmer quenching constant values of CP-1 for the targeted analytes are admirable and the low detection limit (LOD) values for NFT, NZF and TNP are found to be 34.54, 67.79 and 43.93 ppb respectively. Further, the DFT theory is carried out in details to justify the sensing mechanism.

Techniques for remediation of pharmaceutical pollutants using metal organic framework - Review on toxicology, applications, and mechanism

Treatment of recalcitrant and xenobiotic pharmaceutical compounds in polluted waters have gained significant attention of the environmental scientists. Antibiotics are diffused into the environment widely owing to their high usages, very particularly in the last two years due to over consumption during covid 19 pandemic worldwide. Quinolones are very effective antibiotics, but do not get completely metabolized due to which they pose severe health hazards if discharged without proper treatment. The commonly reported treatment methods for quinolones are adsorption and advanced oxidation methods. In both the treatment methods, metal organic frameworks (MOF) have been proved to be promising materials used as stand-alone or combined technique. Many composite MOF materials synthesized from renewable, natural, and harmless materials by eco-friendly techniques have been reported to be effective in the treatment of quinolones. In the present article, special focus is given on the abatement of norfloxacin and ofloxacin contaminated wastewater using MOFs by adsorption, oxidation/ozonation, photocatalytic degradation, electro-fenton methods, etc. However, integration of adsorption with any advanced oxidation methods was found to be best remediation technique. Of various MOFs reported by several researchers, the MIL-101(Cr)-SO₃H composite was able to give 99% removal of norfloxacin by adsorption. The MIL - 88A(Fe) composite and Fe LDH carbon felt cathode were reported to yield 100% degradation of ofloxacin by photo-Fenton and electro-fenton methods respectively. The synthesis methods and mechanism of action of MOFs towards the treatment of norfloxacin and ofloxacin as reported by several investigation reports are also presented.

Highly Luminescent MOF and Its In Situ Fabricated Sustainable Corn Starch Gel Composite as a Fluoro-Switchable Reversible Sensor Triggered by Antibiotics and Oxo-Anions

Frequent use of antibiotics and the growth of industry lead to the pollution of several natural resources which is one of the major consequences for fatality to human health. Exploration of smart sensing materials is highly anticipated for ultrasensitive detection of those hazardous organics. The robust porous hydrogen bonded network encompassing a free-NH₂ moiety, Zn(II)-based metal-organic framework (MOF) (1), is used for the selective detection of antibiotics and toxic oxo-anions at the ppb level. The framework is able to detect the electronically dissimilar antibiotic sulfadiazine and nitrofurazone via fluorescence "turn-on" and "turn-off" processes, respectively. The antibiotic-triggered reversible fluoro-switching phenomena (fluorescence "on-off-on") are also observed by using the fluorimetric method. An extensive theoretical investigation was performed to establish the fluoro-switching response of 1, triggered by a class of antibiotics and also the sensing of oxo-anions. This investigation reveals that the interchange of the HOMO-LUMO energy levels of fluorophore and analytes is responsible for such a fluoro-switchable sensing activity. Sensor 1 showed the versatile detection ability which is reflected by the detection of a carcinogenic nitro-group-containing drug "roxarsone". In view of the sustainable environment along with quick-responsive merit of 1, an in situ MOF gel composite (1@CS; CS = corn starch) is prepared using 1 and CS due to its useful potential features such as biocompatibility, toxicologically innocuous, good flexibility, and low commercial price. The MOF composite exhibited visual detection of the above analytes as well as antibiotic-triggered reversible fluoro-switchable colorimetric "on-off-on" response. Therefore, 1@CS represents a promising smart sensing material for monitoring of the antibiotics and oxo-anions, particularly appropriate for the real-field analysis of carcinogenic drug molecule "roxarsone" in food specimens.

Ferric iron loaded porphyrinic zirconium MOFs on corncob for the enhancement of diuretics extraction

Herein, corncob waste was used as a scaffold for the fabrication of effective adsorbents. Porphyrinic zirconium metal-organic frameworks (MOFs) PCN-223 and PCN-224 constructed by different numbers of Zr6 cluster nodes were grown on the surface of the corncob. Fe (Ш) ions were implanted in the porphyrin ring by post-synthesis modification. The results showed that the extraction capacity of diuretics on PCN-224@corncob containing suitable pore size was larger than that of PCN-223@corncob. The adsorption of diuretics was further enhanced because of the electrostatic effect caused by implantation of Fe (Ш) ions. PCN-224-Fe@corncob was recyclable and selective for the extraction of furosemide (Fur) and bumetanide (Bum). Coupled in-syringe solid phase extraction (IS-SPE) with ultra-performance liquid chromatography (UPLC), an efficient, sensitive, and stable method was established. With a sensitivity between 0.6 and 1.0 μg/L and a recovery between 83.2% and 119.2%, it is used for the analysis of trace amounts of Fur and Bum in weight loss products and environmental water. The functionalized corncob has potential application for the adsorption of diuretics, and the metal ions implantation in MOFs provides a promising strategy for enhancing extraction capacity.