Congo red decomposition by photocatalytic formation of hydroxyl radicals (·OH) using titanium metal–organic frameworks

Bifunctional TiO2 - cellulose based nanocomposites for synergistic adsorptive-photocatalytic removal of methyl orange: Response modelling and optimization

Removal of azo dyes from aquatic environments represents a global challenge. Herein, by utilizing the waste of mandarin peels as a cellulose source (MP500), a bifunctional adsorbent-photocatalyst, TiO2@MP500, has been prepared via a one-pot hydrothermal synthesis. Taking advantage of this dual role, remediation of methyl orange (MO) has been successfully addressed. Characterization tools corroborated the anchoring of TiO2 and the successful synthesis of TiO2@MP500. SEM/EDX/TEM analyses confirmed the formation of TiO2 nanoparticles on the carbonaceous surface. A substantial increase in the BET surface area following TiO2 impregnation was perceived (184.61 m2/g in the case of 3 %TiO2@MP500). Similarly, the thermal stability of the developed composite was notably improved as reflected by the thermogravimetric analysis. XRD analysis corroborated the existence of carbonaceous layer with anatase phase TiO2. Optimization of the adsorbent-photocatalyst performance was approached using the Box-Behnken design. Five factors were premeditated, pH of the MO solution, adsorbent dose, reaction time, the concentration of TiO2, and [MO]. A maximum sorption capacity of 104.2 mg/g was reckoned, with a pseudo-second-order isotherm. Furthermore, the 3 %TiO2@MP500 achieved a decolorization efficiency of 98.87 % in ∼30 min. The 3 %TiO2@MP500 nanocomposite was effectively revived and could be exploited for 6 cycles, bolstering a decolorization efficiency of 90.91 %.

Structural insights of mechanochemically amorphised MIL-125-NH2

In this work, we investigated the response of the metal-organic framework MIL-125-NH2 to ball-milling. Both localised and bulk analyses revealed prolongued ball-milling results in a complete loss of long-range structural order. Investigation of this disorder revealed partial retention of the local bonding of the secondary building unit, suggesting structure collapse progressed primarily through metal-linker bond breakage. We explored the photocatalytic performance of the materials, and examined the materials' band gap using UV-Vis reflectance spectroscopy.

Solar radiation-promoted selective photocatalytic degradation of Congo red dye by a novel amorphous Cr-based metal-organic framework serving as sensor for 2,4,6-trinitrophenol explosive detection

Synthesis of novel benzene-1,2,4-tricarboxylic acid-based chromium metal-organic framework (designated as Cr-BTC MOF) by solvothermal method using water:ethanol:dimethylformamide (1:1:2) as solvent media has been undertaken with an aim to exploit its role as photocatalyst in degradation of some anionic dyes along with sensing potential of some explosives. The MOF has been characterized by Fourier transform infra-red, scanning electron microscopy, Brunauer-Emmett Teller and powder X-Ray diffraction techniques and has shown high thermal stability, upto 373 °C. The prepared MOF was utilized as photocatalyst in selective degradation of Congo red (CR) dye. The effects of pH, source of radiation, initiator and concentration of catalyst were monitored and the results have shown that catalyst exhibits maximum efficiency of 93.3% in the presence of sunlight in neutral medium. The stability and reusability of the catalyst, after four cycles of reusability, renders it to be a highly efficient photocatalyst in the treatment of wastewater under the effect of sunlight. Photoluminescence-detection of explosives viz. 2,4,6-trinitrophenol and nitromethane, has been carried out, wherein Stern-Volmer equation was used to assess the quenching efficiency evaluated. The results have shown exceptional efficiency and selectivity of Cr-BTC MOF towards detection of 2,4,6-trinitrophenol (94%). The reusability has shown the synthesized MOF to display excellent recyclability upto 5 cycles. Minimum inhibitory concentration (MIC) method was investigated to establish their antibacterial efficacy against some Gram-positive and Gram-negative strains. The MOF has showed good efficacy towards Bacillus cereus and Staphylococcus aureus, displaying a MIC value of 7.81 µg/mL, and Pseudomonas aeruginosa (15.625 µg/mL) similar to the standard antibacterial drug, chloramphenicol, thereby establishing their biological efficacy.

Double Hydroxide Nanocatalysts for Urea Electrooxidation Engineered toward Environmentally Benign Products

Recent advancements in the electrochemical urea oxidation reaction (UOR) present promising avenues for wastewater remediation and energy recovery. Despite progress toward optimized efficiency, hurdles persist in steering oxidation products away from environmentally unfriendly products, mostly due to a lack of understanding of structure-selectivity relationships. In this study, the UOR performance of Ni and Cu double hydroxides, which show marked differences in their reactivity and selectivity is evaluated. CuCo hydroxides predominantly produce N2, reaching a current density of 20 mA cmgeo -2 at 1.04 V - 250 mV less than NiCo hydroxides that generate nitrogen oxides. A collection of in-situ spectroscopies and scattering experiments reveal a unique in situ generated Cu(2-x)+-OO-• active sites in CuCo, which initiates nucleophilic substitution of NH2 from the amide, leading to N-N coupling between *NH on Co and Cu. In contrast, the formation of nitrogen oxides on NiCo is primarily attributed to the presence of high-valence Ni3+ and Ni4+, which facilitates N-H activation. This process, in conjunction with the excessive accumulation of OH- ions on Jahn-Teller (JT) distorted Co sites, leads to the generation of NO2 - as the primary product. This work underscores the importance of catalyst composition and structural engineering in tailoring innocuous UOR products.

Porphyrin-Based Metal-Organic Framework Materials: Design, Construction, and Application in the Field of Photocatalysis

Metal-organic frameworks (MOFs) are a novel category of porous crystalline materials with an exceptionally high surface area and adjustable pore structure. They possess a designable composition and can be easily functionalized with different units. Porphyrins with conjugated tetrapyrrole macrocyclic structures can absorb light from ultraviolet to visible light regions, and their structures and properties can be facilely regulated by altering their peripheral groups or central metal ions. Porphyrin-based MOFs constructed from porphyrin ligands and metal nodes combine the unique features of porphyrins and MOFs as well as overcoming their respective limitations. This paper reviewed the design and construction, light absorption and charge transfer pathways, and strategy for improving the photocatalytic performance of porphyrin-based MOFs, and highlighted the recent progress in the field of CO2 reduction, hydrogen evolution, organic synthesis, organic pollutant removal, and nitrogen fixation. The intrinsic relationships between the structure and the property of porphyrin-based MOFs received special attention, especially the relationships between the arrangements of porphyrin ligands and metal nods and the charge transfer mechanism. We attempted to provide more valuable information for the design and construction of advanced photocatalysts in the future. Finally, the challenges and future perspectives of the porphyrin-based MOFs are also discussed.

Cr(VI) and doxorubicin adsorptive capture by a novel bionanocomposite of Ti-MOF@TiO2 incorporated with watermelon biochar and chitosan hydrogel

Biodegradable polymers, biochars and metal organic frameworks (MOFs) have manifested as top prospects for elimination of harmful pollutants. In the current study, Ti-MOF was synthesized and decorated with TiO2 nanoparticles, then embedded into watermelon peel biochar and functionalized with chitosan hydrogel to produce Ti-MOF@TiO2@WMPB@CTH. Various instruments were employed to assure the effective production of the bionanocomposite. The HR-TEM and SEM studies referred to excellent surface porosity and homogeneity of Ti-MOF@TiO2@WMPB@CTH bionanocomposite, with 51.02-74.23 nm. Based on the BET analysis, the mesoporous structure has a significant surface area of 366.04 m2 g-1 and a considerable total pore volume of 11.38 × 10-2 cm3 g-1, with a mean pore size of 12.434 nm. Removal of doxorubicin (DOX) and hexavalent chromium (Cr(VI)) was examined under various experimentations. Pseudo-second order kinetic models in addition to Langmuir isotherm offered the best fitting. Thermodynamic experiments of the two contaminants demonstrated spontaneous and endothermic interactions. After five subsequent adsorption and desorption cycles, Ti-MOF@TiO2@WMPB@CTH bionanocomposite demonstrated an exceptional recyclability for the elimination of DOX and Cr(VI) ions, reaching 97.96 % and 95.28 %, respectively. Finally, the newly designed Ti-MOF@TiO2@WMPB@CTH bionanocomposite demonstrated a high removing efficiency of Cr(VI) ions and DOX from samples of real water.

A protocol of carbonized on-column enrichment for urinary exosomal N-glycans profiling

As a widely present vesicle, exosome plays an important role in lots of biological processes due to its inclusive cargos. In particular, exosome glycan cargo is attracting attentions since its aberrant alteration is closely related to many progressions in diseases. In this work, a novel carbonized packing capillary trap column for urinary exosomal N-glycan enrichment was proposed. The carbonized packing exhibited large specific surface area, mesoporous structure with narrow pore size distribution and abundant carbon for specially interacting with oligosaccharides. Benefitting from all these advantages, the N-glycans deriving from standard glycoproteins or complex human urine exosomes could be identified with high sensitivity and selectivity. Finally, from the glycans identified in healthy volunteers and patients with bladder carcinoma, we observed that 10 of glycans shared by two groups were obvious downregulation and the 18 were upregulation. These results show great potential of capillary trap column as a tool for the enrichment and detection of glycans in exosomal, attracting more attention on disease progression monitoring and biomarker discovery.

Green calcium-based photocatalyst derived from waste marble powder for environmental sustainability: A review on synthesis and application in photocatalysis

Calcium, with its excellent adsorptive property and higher permissible limits in the environment, emerges as an effective wastewater treatment earth metal. Most of the catalysts, photocatalysts, and adsorbents reported in the literature have heavy metal complex, which creates a leaching problem. Majorly, precursors used for the synthesis of heterogeneous catalysts for wastewater treatment are costly. Therefore, the use of such precursors would be not suitable and feasible approach from an economic point of view. This review work is focused on giving an overview of the utilisation of calcium-based catalysts (adsorbents and photocatalyst) for the removal/degradation of various types of dye water pollutants and summarises the reported effects of calcium as a base on the removal efficiency of dopants. In this article, an extensive literature survey is presented on the various photocatalysts developed and the different syntheses involved in their preparation. As the utilisation of marble powder is a green sustainable approach, the scope of various calcium-based photocatalysts and their application is presented. This article also aims for the elementary and inclusive determination of the effect of introducing calcium as a base for different catalysts and adsorbents.

Reusable composite membranes for highly efficient chromium removal from real water matrixes

Natural or industrial hexavalent chromium water pollution continues to be a worldwide unresolved threat. Today, there is intense research on new active and cost-effective sorbents for Cr(VI), but most still exhibit a critical limitation: their powdered nature makes their recovery from water cost and energy consuming. In this work, Al(OH)₃, MIL-88-B(Fe), and UiO-66-NH₂ Cr(VI) sorbents were immobilized into a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymeric substrate to develop an easily reactivable and reusable water filtering technology. The immobilization of the sorbents into the PVDF-HFP porous matrix modified the macro and meso-porous structure of the polymeric matrix, tuning in parallel its wettability. Although a partial blocking of the Cr(VI) adsorptive capacity was observed for of Al(OH)₃ and MIL-88-B(Fe) when immobilized into composite membranes, PVDF-HFP/UiO-66-NH₂ filter (i) exceeded the full capacity of the non-immobilized sorbent to trap Cr(VI), (ii) could be reactivated and reusable, and (iii) it was fully functional when applied in real water effluents.

Soybean Oil Epoxidation Catalyzed by a Functionalized Metal–Organic Framework with Active Dioxo-Molybdenum (VI) Centers

In this work, a functionalized gallium metal–organic framework with active dioxo-molybdenum (VI) centers was evaluated as a catalyst in the epoxidation of soybean oil using tert-butyl-hydroperoxide as an oxidizing agent. The influence of the reaction time, temperature, and concentration of the oxidizing agent was studied, and it was demonstrated that the highest epoxide selectivity was obtained at 110 °C after 4 h of reaction (29% conversion and 91% selectivity) using a soybean oil/oxidizing agent ratio of 1/2. The stability of the metal–organic framework was confirmed by infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy EDS. The stability tests demonstrated that the catalyst could be reused in the catalytic process for the recovery of vegetable oils.

Graphical Abstract

Low temperature curable titanium-based sols for visible light photocatalytic coatings for glass and polymeric substrates

Titanium oxide (TiO2) is a widely used material in photocatalytic coatings in which efficiency generally lies in the ultraviolet (UV) spectrum of light. Sol-gel method provides a simple and versatile...