High-performance catalytic reduction of 4-nitrophenol to 4-aminophenol using M-BDC (M = Ag, Co, Cr, Mn, and Zr) metal-organic frameworks

Quaternization of a Triphenylamine-Based Conjugated Porous Organic Polymer to Immobilize PtCl62- for the Photocatalytic Reduction of 4-Nitrophenol

Photocatalytic reduction of 4-nitrophenol (4-NP) for converting it to nontoxic 4-aminophenol (4-AP) is one of the most efficient approaches for removing toxic 4-NP. Using porous organic polymers (POPs) as the support to immobilize noble metal catalysts has exhibited remarkable reduction performance but is rarely reported. Herein, a cationic triphenylamine-based POP was synthesized by quaternization to immobilize PtCl62- to prepare an efficient photocatalyst named DCM-TPA-Pt for the reduction of 4-NP to 4-AP in the presence of NaBH4. Different from reported methods which realize immobilization by doping or complexing, the support and PtCl62- are combined through electrostatic interaction with milder reaction conditions to produce a photocatalyst in this work. DCM-TPA-Pt shows excellent photocatalytic reduction performance, reaching 99.9% conversion within 3 min, and its pseudo-first-order constant is 0.0305 s-1, surpassing most of the reported photocatalysts. Moreover, DCM-TPA-Pt also exhibits equal reduction efficiency after five continuous cycles, which highlights its potential utilization in practical applications.

Facile synthesis of Cu-based catalysts from Cu3Si and their catalysis properties study

Supported copper species are well-known for their remarkable catalytic properties across numerous reactions. However, the current preparation methods pose challenges for large-scale production. In this study, we present a cost-effective method for the facile preparation of a series of copper-silicon composites using Cu3Si@Si particles as precursors. We evaluate the catalytic properties of these composites in the conversion of 4-nitrophenol to 4-amionphenol. Notably, the Cu@SiOx/Si composite exhibits exceptional catalytic performance, attributed to the synergy effect between Cu and Si, and the formation of a metastable Si-H2 complex that enhances the reaction kinetics. This research introduces a novel approach for creating efficient and stable catalysts for hydrogenation reactions.

High Catalytic Activity of CoxPt100-x Alloys for Phenolic Compound Reduction

In this study, we report the influence of the Pt concentration in CoxPt100-x alloys on the catalytic activity of the alloys for 4-nitrophenol (4-NP) reduction. More precisely, a series of CoxPt100-x alloys with a Pt concentration ranging between 60% and 95% were prepared using electrodeposition at controlled potentials from stable hexachloroplatinate aqueous solution. The Pt concentration was tuned by varying the electrodeposition potential from -0.6 to -0.9 V. The changes in the CoxPt100-x alloy microstructure and crystalline structure have been investigated using SEM and TEM analysis. Our results show that the microstructure and the crystalline structure of the as-prepared materials do not depend on the electrodeposition potential. However, the catalytic activity of CoxPt100-x alloys is closely correlated with the potential applied during electrochemical synthesis, hence the Pt content. We demonstrated that the synthesized materials present a high catalytic activity (approx. 90%) after six cycles of reusability despite the fact that the Pt content of the as-prepared alloys decreases. The easy preparation method that guarantees more than 97% catalytic activity of the CoxPt100-x alloys, the easy recovery from solution, and the possibility of reusing the CoxPt100-x alloys are the benefits of the present study.

The Promise and Potential of Metal-Organic Frameworks and Covalent Organic Frameworks in Vaccine Nanotechnology

The immune system's complexity and ongoing evolutionary struggle against deleterious pathogens underscore the value of vaccination technologies, which have been bolstering human immunity for over two centuries. Despite noteworthy advancements over these 200 years, three areas remain recalcitrant to improvement owing to the environmental instability of the biomolecules used in vaccines─the challenges of formulating them into controlled release systems, their need for constant refrigeration to avoid loss of efficacy, and the requirement that they be delivered via needle owing to gastrointestinal incompatibility. Nanotechnology, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), has emerged as a promising avenue for confronting these challenges, presenting a new frontier in vaccine development. Although these materials have been widely explored in the context of drug delivery, imaging, and cancer immunotherapy, their role in immunology and vaccine-related applications is a recent yet rapidly developing field. This review seeks to elucidate the prospective use of MOFs and COFs for biomaterial stabilization, eliminating the necessity for cold chains, enhancing antigen potency as adjuvants, and potentializing needle-free delivery of vaccines. It provides an expansive and critical viewpoint on this rapidly evolving field of research and emphasizes the vital contribution of chemists in driving further advancements.

Decoration of viscose fibers with silver nanoparticle-based titanium-organic framework for use in environmental applications

To effectively remove pharmaceuticals, nitroaromatic compounds, and dyes from wastewater, an efficient multifunctional material was created based on silver nanoparticles (Ag) and MIL-125-NH2 (MOF) immobilized on viscose fibers (VF) as a support substrate. Firstly, silver nanoparticles (Ag) were immobilized on the surface of viscose fibers (VF) via in situ synthesis using trisodium citrate (TSC) as a reducing agent to create (VF-Ag). Then, VF and VF-Ag were decorated with the titanium metal-organic framework MIL-125-NH2 (MOF) to create VF-MOF and VF-Ag-MOF. The influence of VF-Ag, VF-MOF, and VF-Ag-MOF on the sonocatalytic or sonophotocatalytic degradation of sulfa drugs was investigated. The results show that VF-Ag-MOF showed excellent sonocatalytic and sonophotocatalytic activity towards the degradation of sulfa drugs compared to VF-Ag and VF-MOF. Furthermore, sonophotodegradation showed a dramatic enhancement in the efficiency of degradation of sulfa drugs compared to sonodegradation. The sonophotodegradation degradation percentage of sulfanilamide, sulfadiazine, and sulfamethazine drugs in the presence of VF-Ag-MOF was 65, 90, and 95 after 45 min of ultrasonic and visible light irradiation. The catalytic activity of VF-Ag, VF-MOF, and VF-Ag-MOF was evaluated through the conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP). The results demonstrate that VF-Ag-MOF had the highest catalytic activity, followed by VF-Ag and VF-MOF. The conversion percentage of 4-NP to 4-AP was 69%. The catalytic or photocatalytic effects of VF-Ag, VF-MOF, and VF-Ag-MOF on the elimination of methylene blue (MB) dye were investigated. The results demonstrate that VF-Ag-MOF showed high efficiency in removing the MB dye through the reduction (65%) or photodegradation (71%) after 60 min. VF-Ag-MOF composites structure-activity relationships represent that doping within silver NPs enhanced the photocatalytic activity of MIL-125-NH2, which could be explained as follows: (i) Due to the formation of a Schottky barrier at the junction between MIL-125-NH2 and Ag NPs, the photogenerated electrons in the conduction band of MIL-125-NH2 were supposed to be quickly transferred to the valence band of the Ag NPs, and subsequently, the electrons were transferred to the conduction band of Ag NPs. This considerable electron transferring process, which is reported as Z scheme heterojunction, can efficiently suppress the recombination of electron/hole pairs in VF-Ag-MIL-125-NH2 composites. (ii) Sufficient separation between the photogenerated charge carriers (holes and electrons) and avoiding their recombination enhanced the photocatalytic activity of composites.

Degradation of reactive red 198 dye from aqueous solutions by combined technology advanced sonofenton with zero valent iron: Characteristics/ effect of parameters/kinetic studies

Dyes are one of the most common contaminants in industrial effluents, whose continuous release into the environment has become an increasing global concern. In this work, nanoparticles of zero-valent iron (NZVI) were synthesized using the chemical regeneration method ،and were utilized for the first time as a catalyst in the advanced Sono-Nano-Fenton hybrid method for the decomposition of Reactive Red 198 (RR198). The properties of zero-valent iron nanoparticles were analyzed using SEM and XRD. The effect of pH, initial dye concentration, nanoparticle dosage, zero-valent iron and H2O2 concentration on the decomposition efficiency of Red Reactive 198 was investigated. Comparing the efficiency of Reactivate 198 dye degradation in Sonolysis, Sono-NZVI, Sono-H2O2 and Sono-Nano Fenton processes showed that 97 % efficiency was achieved by the Sono-Nano Fenton process in 60 min. The kinetics of the removal process showed that this process follows pseudo-first-order kinetics and the Langmuir-Hinshelwood model. The results indicate that the effectiveness of the ultrasonic process in removing resistant organic pollutants such as dyes increases tremendously with the synergy of the Fenton process.

Green valorization of PET waste into functionalized Cu-MOF tailored to catalytic reduction of 4-nitrophenol

Metal-organic frameworks (MOFs) are attractive functional materials due to their high surface area, high porosity, and flexible compositions. However, the high precursor cost and complex synthetic processes hinder their large-scale applications. Herein, a novel green approach has been developed toward the synthesis of Cu-based MOF by a solvent-free mechano-synthesis method and utilizing consumed polyethylene terephthalate (PET)-derived benzenedicarboxylate (BDC) as the linker. The as-prepared CuBDC and aminated CuBDC (CuBDC-NH2) act as green catalysts for the reduction of deleterious 4-nitrophenol (4-NP) into the value-added 4-aminophenol (4-AP). Compared with CuBDC, CuBDC-NH2 shows increased adsorption capability and reduction efficiency. The mechanism and thermodynamic studies suggest that the adsorption of 4-NP on CuBDC-NH2 is an endothermic, spontaneous, favorable, and physical adsorption process. Furthermore, CuBDC-NH2 can expedite the reduction of 4-NP by participating in an adsorptive catalytic process. With the CuBDC-NH2 catalyst, the catalytic normalized kinetic rate of 4-NP was achieved 11.28 mol/min. mg, outperforming state-of-the-art catalysts, and a complete reduction occur in 5 min for a concentrated effluent (200-ppm 4-NP). The plastic waste-derived MOF-mediated catalytic valorization of organic pollutants demonstrated here opens an avenue for the green recycling/utilization of plastic waste, providing meaningful insights into the sustainable management of organic pollutants in wastewater.

In-situ preparation of sulfonated carbonaceous copper oxide-zirconia nanocomposite as a novel and recyclable solid acid catalyst for reduction of 4-nitrophenol

The missing-linker defects of UiO-66 were exploited to covalently anchor Cu nanoclusters (Cu/UiO-66). The molecular interactions between the metals and oxides as copper-zirconia interfaces in Cu/UiO-66 are essential for heterogeneous catalysis, leading to remarkable synergistic impacts on activity and selectivity. Homogeneously distributed carbonaceous mixed metal oxides (CuO/ZrO₂@C) nanocomposite was prepared via carbonization of the Cu/UiO-66 at 600 °C for 3 h in air. To enhance the acidity properties of the CuO/ZrO₂@C nanocomposite, a small amount of sulfuric acid was added and heated at 150 °C under an N₂ atmosphere (CuO/ZrO₂-SO₃H@C). The synthesised Cu/UiO-66 and CuO/ZrO₂-SO₃H@C catalysts were used as novel catalysts in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The Cu/UiO-66 and CuO/ZrO₂-SO₃H@C catalysts displayed complete conversion of the 4-NP solution during (4 and 2 min) stirring at room temperature, respectively. These two catalysts exhibited a high reduction rate of 8.61 × 10^-3 s^-1, and 18.3 × 10^-3 s^-1, respectively. The X-ray photoelectron spectroscopic (XPS) analysis showed the charge of copper atoms in the Cu/UiO-66 catalyst was Cu⁰/Cu^II and in the CuO/ZrO₂-SO₃H@C catalyst was Cu^I/Cu^II with nearly the same ratio (65/35). The particle size and the elemental composition of the CuO/ZrO₂-SO₃H@C catalyst were analysed by using high resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDS), and elemental mapping, respectively. The key point beyond the high catalytic activity and selectivity of the CuO/ZrO₂-SO₃H@C catalyst is both the carbon-metal oxides heterojunction structure that leads to good dispersion of the CuO and ZrO₂ over the carbon sheets, and the high acidity properties that come from the combination between the Brønsted acid sites from sulfuric acid and Lewis acid sites from the UiO-66. The catalysts exhibited good recyclability efficiency without significant loss in activity, indicating their good potential for industrial applications.