Synergetic Molecular Oxygen Activation and Catalytic Oxidation of Formaldehyde over Defective MIL-88B(Fe) Nanorods at Room Temperature.

Defective MIL-88B(Fe) nanorods are exploited as exemplary iron-bearing metal-organic framework (MOF) catalyst for molecular oxygen (O2) activation at ambient temperature, triggering effective catalytic oxidation of formaldehyde (HCHO), one of the major indoor air pollutants. Defective MIL-88B(Fe) nanorods, growing along the [001] direction, expose abundant coordinatively unsaturated Fe-sites (Fe-CUSs) along extended hexagonal channels with a diameter of ca. 5 Å, larger enough for the diffusion of O2 (3.46 Å) and HCHO (2.7 Å). The Lewis acid-base interaction between Fe-CUSs and accessible HCHO accelerates the FeIII/FeII cycle, catalyzing Fenton-like O2 activation to produce reactive oxidative species (ROSs), including superoxide radicals (•O2-), hydroxyl radicals (•OH), and singlet oxygen (1O2). Consequently, adsorbed HCHO can be oxidized into CO2 with a considerable mineralization efficiency (over 80%) and exceptional recyclability (4 runs, 48 h). Dioxymethylene (CH2OO), formate (HCOO-) species, and formyl radicals (•CHO) are recorded as the main reaction intermediates during HCHO oxidation. HCHO, H2O, and O2 are captured and activated by abundant FeIII/FeII-CUSs as acid/base and redox sites, triggering synergetic ROS generation and HCHO oxidation, involving cooperative acid-base and redox catalysis processes. This study will bring new insights into exploiting novel MOF catalysts for efficient O2 activation and reliable indoor air purification at ambient temperature.

Microbial Fuel Cell-Based Biological Oxygen Demand Sensors for Monitoring Wastewater: State-of-the-Art and Practical Applications.

Environmental pollution has been a continuous threat to sustainable development and global well-being. It has become a significant concern worldwide to combat the ecological crisis using low-cost innovative technologies. Biological oxygen demand (BOD) is a key indicator to comprehend the quality of water to guarantee environmental safety and human health; however, none of the present technologies are capable of online monitoring of the water at the source. Microbial fuel cells (MFC) are a promising technology for simultaneous power generation and wastewater treatment. MFCs have also been shown in fascinating applications to measure and detect the toxic pollutants present in wastewater. These are the bioreactors where exoelectrogenic microorganisms catalyze the conversion of the inherent chemical energy stored in organic compounds to electrical energy. Sensors employ energy conversion to measure BOD, which is considered an international index for the detection of organic material load present in wastewater. The MFC-based BOD sensors have gone through a wide range of advancement from mediator to mediator-less, double chamber to single-chamber, and large size to miniature. There have been detailed studies to improve the accuracy and reproducibility of the sensors for commercial applications. Additionally, multistage MFC-based BOD biosensors and miniature MFC-BOD sensors have also been ubiquitous in recent years. A considerable amount of work has been carried out to improve the performance of these devices by fabricating the proton exchange membranes and altering catalysts at the cathode. However, there remains a dearth for the fabrication of the devices in aspects like suitable microbes, proton exchange membranes, and cheaper catalysts for cathodes for effective real-time monitoring of wastewater. In this review, an extensive study has been carried out on various MFC-based BOD sensors. The efficiency and drawbacks associated with the different MFC-based BOD sensors have been critically evaluated, and future perspectives for their development have been investigated. The breadth of work compiled in this review will accelerate further research in MFC-based BOD biosensors. It will be of great importance to broad ranges of scientific research and industry.

Homogeneous photochemical water oxidation with metal salophen complexes in neutral media.

The development of water oxidation catalysts based on Earth-abundant metals that can function at neutral pH remains a basic chemical challenge. Here, we report that salophen complexes with Ni(ii), Cu(ii), and Mn(ii) can catalyse photochemical water oxidation to molecular oxygen in the presence of [Ru(bpy)3]2+ as a photosensitizer and Na2S2O8 as an oxidant in phosphate buffer of pH 7.0. Experimental results including CV, SEM, EDS, ESI-MS, and DLS measurements on the metal salophen complex-catalysed water oxidation to oxygen suggest that the catalytic activity of the catalysts is molecular in origin.

Cationic nickel metal-organic frameworks for adsorption of negatively charged dye molecules.

Industrial dye effluents with low biodegradability are highly toxic and carcinogenic on both human and aquatic lives, thus they are detrimental to the biodiversity of environment. Herein, this data set presents the potential of cationic Nickel based MOFs in the adsorption of charged and neutral dye molecules. Data set include a concise description of experimental conditions for the synthesis of imidazolium ligands, 1,3-bis(4-carboxyphenyl)imidazolium chloride (H2L+Cl-) and 1,3-bis(3,5-dicarboxyphenyl)imidazolium chloride (H4L+Cl-), and MOFs. The data show that the two Nickel MOFs, 1 and 2, synthesized from imidazolium ligands are cationic frameworks. The adsorption and analysis data show that the cationic MOFs exhibit efficient adsorptive removal capacity for positively charged dyes, adsorbing up to 81.08% and 98.65% of Methyl orange and Congo red, respectively.

Selective and adsorptive removal of anionic dyes and CO2 with azolium-based metal-organic frameworks.

The positively charged azolium moieties make imidazolium linker an ideal linker for the construction of cationic metal-organic frameworks because the ligand induces cationic environments in the frameworks. Therefore, we employed two imidazolium ligands, 1,3-bis(4-carboxyphenyl)imidazolium chloride (H2L+Cl¯) and 1,3-bis(3,5-dicarboxyphenyl)imidazolium chloride (H4L+Cl¯), to synthesize two nickel azolium-based MOFs, 1 and 2. The as-synthesis MOFs were characterized by PXRD, TGA, FE-SEM, HR-TEM, FTIR and BET measurements. By applying 1 and 2 in liquid phase adsorption of charged molecules of dyes, they successfully exhibit remarkable efficiency for adsorptive removal of anionic dyes, Methyl orange (MO), Congo red (CR), and Orange II sodium salt (OS), from aqueous solution. The framework proves efficient in photocatalytic degradation of anionic dye. Furthermore, in the gaseous phase adsorption, 1 and 2 selectively adsorb CO2 over CH4 due to the higher quadrupole moment of CO2. Overall, the results show that azolium-based MOFs have potential applications for adsorptive removal of charged organic contaminants from both aqueous and gaseous environment.