Anchoring of copper complex in MCM-41 matrix: a highly efficient catalyst for epoxidation of olefins by tert-BuOOH

Anchoring of Copper(II)-Schiff Base Complex in SBA-15 Matrix as Efficient Oxidation and Biomimetic Catalyst

A new mononuclear Cu(II) complex [Cu(L2)(H2O)2], where L is the Schiff base 2-[2-(3-bromopropoxy)benzylideneamino] benzoic acid, was synthesized and covalently anchored onto an amino-functionalized SBA-15 mesoporous silica in order to obtain an efficient heterogeneous catalyst. The elemental, structural, textural and morphological characterization confirmed the coordination of the central Cu(II) ion with two ligands and two H2O molecules in the synthesized complex and its successful immobilization into the inner pore surface of the NH2-functionalized support without the loss of the mesoporous structure. The catalytic activity of the free or immobilized Cu(II) complex was tested in the oxidation of cyclohexene with H2O2 under an air atmosphere and the dismutation reaction of the superoxide radical anions with very good results. In addition, catalyst reuse tests claim its suitability in alkene oxidation processes or as a biomimetic catalyst.

Simulated Enzyme Activity and Efficient Antibacterial Activity of Copper-Doped Single-Atom Nanozymes

Nanozymes with good biocompatibility are novel antibacterial agents because they mimic the structure and properties of enzymes and destroy bacterial structures by generating reactive oxygen species in large quantities. Herein, we synthesized a Cu single-atom nanozyme (Cu-N-C) with intrinsic peroxidase- and oxidase-like activities. Cu-N-C can generate ·OH and O₂^·- during oxidase-catalyzed reactions, which have good antibacterial effects. Meanwhile, the antimicrobial performance can be further enhanced by light emitting diode light incubation due to photocatalysis. Lethal disruption of the membrane structure was confirmed by biofilm staining and scanning electron microscopy analysis. Notably, the antibacterial effect of Cu-N-C (MIC = 16 μg/mL) was significantly better than that of vancomycin (MIC = 1500 μg/mL), a commonly used drug for methicillin-resistant Staphylococcus aureus, and Cu-N-C outperformed the positive control cephalexin and gentamicin in terms of resistance development (27.3% less production of drug-resistant bacteria). Good biocompatibility was also verified using the MTT method, hemolysis analysis, and routine blood measurements in mice. The results of this work suggest that Cu-N-C has great potential for clinical applications as an efficient metal antimicrobial agent.

Copper-complexed dipyridyl-pyridazine functionalized periodic mesoporous organosilica as a heterogeneous catalyst for styrene epoxidation

A new heterogeneous catalyst has been synthesized by immobilization of a copper complex on dipyridyl-pyridazine functionalized periodic mesoporous organosilica (dppz-vPMO). This ordered support was first prepared by a co-condensation reaction between vinyltriethoxysilane and 1,2-bis(trimethoxysilyl)ethane and further post-functionalized through a hetero Diels-Alder reaction with 3,6-di-2-pyridyl-1,2,4,5-tetrazine. Techniques such as XRD, N₂ isotherms, TEM, ¹³C NMR, XPS and DRIFT, among others, were employed to characterize the surface functionalized materials. These results have proven the ordered mesostructure of the materials as well as the presence of novel nitrogen-chelating heterocyclic compounds on the pore surface after the post-modification process. Additionally, the successful anchoring of a copper complex on the dipyridyl-pyridazine (dppz) ligands has been confirmed. The resulting material was evaluated as a heterogeneous catalyst in the epoxidation of styrene using tert-butylhydroperoxide (TBHP) as an oxidant. Under the optimized reaction conditions, Cu@dppz-vPMO showed a high styrene conversion (86.0%) and a remarkable selectivity to styrene oxide (41.9%). Indeed, this catalyst provided excellent catalytic results in terms of stability, reaction rate, conversion and selectivity compared to other bipyridine-like copper catalysts.

Immobilization of Zn4 complex on functionalized Layered HUS-7: Synthesis, Structural Investigation and Catalytic Activity

Tetranuclear Zn (Zn4) complex was selected for the immobilization on novel layered Hiroshima University Silicate (HUS)-7. Modification of HUS-7 was carried out with sulfopropylsilyl agent followed by Zn4 complex incorporation....

Porous organic-inorganic hybrid materials for catalysis, energy and environmental applications

Introduction of organic functionalities into the porous inorganic materials make the resulting hybrid porous framework not only more flexible and hydrophobic, but also provide additional scope for further functionalization, which...

Encapsulation of an Anionic Surfactant into Hollow Spherical Nanosized Capsules: Size Control, Slow Release, and Potential Use for Enhanced Oil Recovery Applications and Environmental Remediation

A new platform that allows encapsulation of anionic surfactants into nanosized capsules and subsequent release upon deployment is described. The system is based on DOWFAX surfactant molecules incorporated into sub-100 nm hollow silica nanoparticles composed of a mesoporous shell. The particles released 40 wt % of the encapsulated surfactant at 70 °C compared to 24 wt % at 25 °C after 21 and 18 days, respectively. The use of the particles for subsurface applications is assessed by studying the effectiveness of the particles to alter the wettability of hydrophobic surfaces and reduction of the interfacial tension. The release of the surfactant molecules in the suspension reduces the contact angle of a substrate from 105 to 25° over 55 min. A sustained release profile is demonstrated by a continuous reduction of the interfacial tension of an oil suspension, where the interfacial tension is reduced from 62 to 2 mN m^-1 over a period of 3 days.

Copper (triazole-5-yl)methanamine complexes onto MCM-41: the synthesis of pyridine-containing pseudopeptides through the 6-endo-dig cyclization of 1,5-enynes

An efficient approach for the synthesis of immobilized copper (triazole-5-yl)methanamine complexes onto MCM-41 (Cu@TZMA@MCM-41), as a novel recyclable nanocatalyst, is described. This nanocatalyst was used for the synthesis of pyridine-containing pseudopeptides through a sequential Ugi/nucleophilic addition/1,5-enyne cyclization reaction and elicited good-to-excellent yields. The nanocatalyst was fully characterized by SEM, EDS, TEM, BET, ICP-OES, TGA, and XRD techniques. Furthermore, the catalyst was recovered by simple filtration and could be used for at least 5 cycles without significant loss of activity.

Palladium-Schiff Base Complexes Encapsulated in Zeolite-Y Host: Functionality Controlled by the Structure of a Guest Complex

A series of palladium complexes of tetradendate Schiff base ligands L1 ( N,N'-bis(salicylidene)phenylene-1,3-diamine) and its derivatives L2 and L3 have been synthesized by using the "flexible ligand method" within the supercage of zeolite-Y. These complexes in both their free and encapsulated states have been thoroughly characterized with the help of different characterization tools such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR, and UV-vis spectroscopic studies. All these encapsulated complexes are identified with a dramatic red shift of the d-d transition in their electronic spectra when compared with their free states. Theoretical as well as experimental studies together suggest a substantial modification of the structural parameters of square planar Pd(II)-Schiff base complexes upon encapsulation within the supercage of zeolite-Y. Encapsulated complexes are also subject to show modified catalytic activities toward the Heck reaction. These heterogeneous catalysts can easily be separated from the reaction mixture and reused.

Selective synthesis of benzoquinones over Cu(ii)-containing propylsalicylaldimine functionalized mesoporous solid catalysts

An eco-friendly and highly active mesoporous CSASBA-15(0.2) has unprecedented catalytic activity, among other CSA functionalized solid catalysts, for the selective synthesis of benzoquinones with 98–100% selectivity.

Theoretical Studies of the Zeolite-Y Encapsulated Chlorine-Substituted Copper(II)phthalocyanine Complex on the Formation Glycidol from Allyl Alcohol

Density functional theory (DFT) used to study the encapsulation of copper(II)phthalocyanine and chlorine-substituted copper(II)phthalocyanine to a zeolite-Y framework. Changes occurring in the redox properties, as well as the red shift of the time-dependent DFT (TD-DFT) spectra, point out the influence of encapsulation on the geometric parameters of the complexes. Also, the TD-DFT calculations show good agreement with the energy changes occurred in the highest occupied molecular orbital and lowest unoccupied molecular orbital. DFT-based descriptors are used for scrutinizing the reactivity of the encapsulated complexes and a mechanism of the glycidol formation is proposed based on the energetics involved in the transformation.

Designing a biomimetic catalyst for phenoxazinone synthase activity using a mesoporous Schiff base copper complex with a novel double-helix morphology

A mesoporous copper complex was synthesized with a novel double helix morphology and successfully utilized as a biomimetic catalyst for phenoxazinone synthase activity.

Microwave-assisted one-pot functionalization of metal–organic framework MIL-53(Al)-NH2 with copper(ii) complexes and its application in olefin oxidation

A simple and rapid functionalization of MOF via microwave-assisted one-pot synthesis afforded a Cu(ii)-Schiff-base-MOF as an efficient catalyst for olefin oxidation.

Valence state alternation of copper species doped in HY zeolite as revealed by paramagnetic relaxation enhancement NMR spectroscopy

Paramagnetic relaxation enhancement (PRE) solid-state NMR (ssNMR) was used to monitor the valence state alternation of copper species doped in HY zeolite during catalytic reaction processes. The combination of PRE ssNMR and in-situ NMR spectroscopy facilitates the detection of copper species as well as the monitoring of evolution from reactants, intermediates to products in heterogeneously catalyzed processes, which is of great importance for elucidating the detailed catalytic reaction mechanism.

Hydrogen bond-directed encapsulation of metalloporphyrin into the microcages of zeolite imidazolate frameworks for synergistic biomimetic catalysis

In efforts to replicate the 3D model and desirable function of haemoglobin, the zeolite imidazolate framework (ZIF-8) was delineated for an ideal host matrix to accommodate custom-designed porphyrin molecules via hydrogen bonding.

Heterogeneous O-arylation of nitroarenes with substituted phenols over a copper immobilized mesoporous silica catalyst

Highly efficient heterogeneous mesoporous silica based Cu-catalyst has been designed forO-arylation of phenol using nitroarene to afford unsymmetrical diarylethers. It can be recycled up to 5 times without any significant loss of catalytic activity.

Mesoporous materials: versatile supports in heterogeneous catalysis for liquid phase catalytic transformations

This review article provides an overview of recently reported liquid phase heterogeneous catalytic reactions performed over mesoporous materials, along with their different synthesis strategies and critical role in environment-friendly green catalysis.

Mesoporous TUD-1 supported indium oxide nanoparticles for epoxidation of styrene using molecular O2

Activation of molecular O₂ by metal or metal oxide nanoparticles is an area of recent research interest.

Sulfonated Schiff base dinuclear and polymeric copper(ii) complexes: crystal structures, magnetic properties and catalytic application in Henry reaction

Aqueous medium syntheses and nitroaldol catalytic studies of three pseudohalide bridged copper(ii) complexes characterized by single crystal X-ray structure analysis and variable temperature magnetic studies are reported.