Leveraging the photocatalytic Cr (VI) reduction by an IRMOF-3@NH2-MIL-101 (Fe) heterostructure based on interfacial Lewis acid-base interaction.

A strategy to enhance the photocatalytic performance of metal-organic framework (MOF) based systems for the efficient elimination of Cr(VI) ions from polluted water under visible light irradiation has been developed by constructing MOF@MOF heterojunctions. Specifically, IRMOF-3 was grown in situ around NH2-MIL-101(Fe) based on interfacial Lewis acid-base interaction using 2-aminoterephthalic acid (ATA) as a linker, resulting in the formation of a MOF@MOF heterojunction, designated as IRMOF-3@NH2-MIL-101(Fe). In comparison to individual MOFs, the IRMOF-3@NH2-MIL-101(Fe) heterojunction exhibited a significantly higher photocatalytic reduction efficiency for Cr(VI), achieving a reduction of 95.98% within 120 min under visible-light irradiation. This performance surpasses that of individual MOFs and most reported photocatalysts. Additionally, the mechanism underlying Cr(VI) reduction by IRMOF-3@NH2-MIL-101(Fe) was comprehensively elucidated by analyzing optoelectronic properties, energy band structure, and structural results. It is worth noting that this study represents the first documented instance of photocatalytic Cr(VI) reduction utilizing IRMOF-3 and its interaction with NH2-MIL-101(Fe). The MOF@MOF photocatalyst, leveraging the synergistic effects of its various components, holds great promise for efficiently removing harmful pollutants from water and finds significant potential applications in environmental remediation.

Understanding the photo-sensitive essence of organic-inorganic hybrids for the targeted detection of azithromycin.

Being a macrolide antibiotic, the antiviral and anti-inflammatory properties of azithromycin (AZM) were taken advantage of during the COVID-19 pandemic which led to the overuse of AZM resulting in excessive release and accumulation in the waterways and ecosystem causing unpleasant threats to humankind. This demands the necessity for a highly sensitive material being capable of recognizing AZM in wastewater. Mindful of the optical attributes of organic ligand structures, we have constructed a hybrid material by chelating Zn2+ with pyridyl benzimidazole (PBI). The prepared sensor material ZnPBI was characterized using various microscopic and spectroscopic techniques including XRD, FT-IR, HR-SEM, HR-TEM, etc. The proposed sensor material exhibited proficient detection performance selectively towards AZM with a very low detection limit of 72 nM. Two linear ranges between 0 - 70 µM and 70-100 µM were observed corresponding to two different mechanistic pathways. To the best of our knowledge, the utilization of a metal-organic complex (MOC) for the fluorometric detection of AZM has not been explored so far. It is creditworthy to cite that the long-term structural stability of the sensor material was maintained for 100 days in water and it can be reused three times without any depreciation in the sensing activity. A combination of energy transfer routes, adsorption and electrostatic interactions for AZM detection are described experimentally and theoretically which provides insights into the role of MOC as sensing probes.

A luminous strategy for the recognition of toxic antibiotics in water via efficient energy transfer.

Fluoroquinolones (FQs) are the class of Antibiotics (ABs) that have been extensively used worldwide for the treatment of diseases caused by bacterial infections. In India, most of these untreated ABs and their unused metabolites present in treated and untreated wastewater end up in agricultural land and water bodies. This can accelerate the problem of antimicrobial resistance in the community. Hence, we aim to develop a cost-effective sensor to detect and monitor the presence of such drugs in water bodies. We have prepared a chemically reduced graphene oxide (rGO) integrated luminescent cerium metal-organic framework (MOF) that specifically targets and recognizes ciprofloxacin (CPFX), norfloxacin (NFX), and ofloxacin (OFX) achieving excellent sensing activity. A remarkable quenching of the fluorescence of MOF composite was observed upon interaction with CPFX, NFX, and OFX with 57.9, 46.3, and 51.6 ppb as limits of detection, respectively, through a Forster resonance energy transfer from the Ce-MOF to the analytes. The applicability of the sensor was also examined with real-time samples collected from the rivers of Chennai city and the MOF probe exhibited an appreciable recovery of results. This is the first study on Ce-MOF-based rGO composite providing a solid rationale for fluorescence detection of FQs with exceptional quenching efficiency and very high sensitivity for monitoring FQs in water bodies even in diluted conditions.