Plug-and-Play Heterogeneous Catalysis Enabled by Metal–Organic Cage-Crosslinked Polymers

The immobilization of homogeneous catalysts onto solid supports to improve recyclability while maintaining catalytic efficiency is often a trial-and-error process limited by poor control of the local catalyst environment and a lack of modular strategies to append catalysts to support materials. Here, we introduce a “plug-and-play” heterogenous catalysis platform that overcomes these challenges. Our approach leverages the well-defined interiors of self-assembled Pd12L24 metal–organic cages/polyhedra (MOCs): through a simple combination of catalyst-ligands, polymeric ligands, and spacer ligands, we demonstrate facile self-assembly of a diverse range of polymer gels featuring endohedrally-catalyst-functionalized junctions. Through decoupling catalyst incorporation and environment from the physical properties of the support (polymer matrix), this simple strategy is shown to enhance the recyclability of various catalyst systems (e.g., TEMPO-catalyzed oxidation and Au(I)-catalyzed cyclization) and enable catalysis in environments where homogeneous catalyst analogs are not viable.

Oxidation of Toluene on Supported and Unsupported LaCoO3 Perovskites Catalyst

Perovskite type oxide are known to be catalysts for a number of reactions such as total and partial oxidation, hydrocracking, hydrogeneous, hydrogenolysis and reduction etc. Efforts has largely been directed towards synthesis of unsupported and supported perovskites oxides of moderates or high specific area, their bulk and surface properties and their role in heterogenous catalysis. Oxidation of aromatic and aliphatic hydrocarbon over LaMO3 (M=Al, Ni, Mn, Co, Fe, Cr etc.) perovskites have been studied. Vapour phase catalytic oxidation of toluene over perovskites Viz., LaCoO3, LaCoO3/ SiO2 and LaCoO3/Al2O3 has been studied. The characterization of the catalyst was carried out using technique Viz. I.R., Surface area, Packing density. Surface acidity, Surface basicity. The surface area measurements in the temperature range 350ºC to 600ºC. The maximum surface area & maximum activity was observed at 450ºC. The heterogeneous catalytic vapour phase oxidation of toluene give benzaldehyde, benzoic acid, maleic acid and CO2 as products over LaCoO3 and LaCoO3 supported on Al2O3 and SiO2 as catalyst. The LaCoO3 supported on Al2O3 has been found to be the most active and selective catalyst giving 84.0% selectivity for benzaldehyde at 450⁰C with surface area 78.9m2/g. The overall Kinetic analysis indicate that the oxidation of Toluene to benzaldehyde is first order. The order of catalytic reactivity is LaCoO3/Al2O3 > LaCoO3/ SiO2 > LaCoO3.

Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

In the past two decades, metal fluorides have gained importance in the field of heterogenous catalysis of bond activation reaction, e.g., hydrofluorination. One of the most investigated metal fluorides is AlF3. Together with its chlorine-doped analogon aluminiumchlorofluoride (AlClxF3−x, x = 0.05–0.3; abbreviated ACF), it has attracted much attention due to its application in catalysis. Various surface models for α-AlF3 and their chlorinated analogues (as representatives of amorphous ACF) are investigated with respect to their Lewis acidity of the active centres. First-principle density functional theory (DFT) methods with dispersion correction are used to determine the adsorption structure and energy of the probe molecules CO and NH3. The corresponding vibrational frequency shift agrees well with the measured values. With this insight we predict the local structure of the active sites and can clarify the importance of secondary interactions to the local anionic surrounding of the catalytic site.

Green synthesis of Microalgal biomass-silver nanoparticles composite showing antimicrobial activity and heterogenous catalysis of nitrophenol reduction

In this study we have demonstrated an integrated approach for utilization of microalga Scenedesmus sp, generated during CO2 sequestration, in fabrication of catalytic and antimicrobial silver nanoparticles composite. The algal biomass was grown in open raceway pond of 30,000 L scale for CO2 sequestration, after which it was harvested and dried. The dried biomass served as a reducing and immobilizing agent for silver nanoparticles. The biomass-silver nanoparticles composite was used for the first time, as a heterogenous catalyst for reduction of a prominent industrial pollutant, p-Nitrophenol, in aqueous medium under ambient condition. Series of experiments were conducted to evaluate the effect of calcination temperature, load and reuse of the material on its catalytic efficiency. The calcined composite material was found to be an excellent catalyst for reduction of p-Nitrophenol. As low as 5 mg mL− 1 calcined material could catalyse the reduction of more than 95% p-Nitrophenol at the rate of 0.60 mg L− 1 min − 1 in aqueous solution at 10 ppm concentration. The efficiency of catalysis was evaluated for ten cycles of reuse. The material was found to be a potential candidate as a reusable heterogenous catalyst for designing continuous flow system for remediation of industrial effluents rich in p-Nitrophenol. Furthermore the material served as a good antimicrobial agent against pathogenic bacteria and fungi. Two strains each of gram + ve and gram –ve bacteria and three strains of fungi were used in the antimicrobial studies using well diffusion method.

Noble-metal based single-atom catalysts for the water-gas shift reaction

Single-atom catalysts (SACs) have attracted great attention in heterogenous catalysis. In this Feature Article, we summarize the recent advances of typical Au and Pt-group-metal (PGM) based SACs and their applications...

Non-noble MNP@MOF: Synthesis and Applications to Heterogenous Catalysis

Transition metals have a long a history in heterogeneous catalysis. Noble or precious transition metals have been widely used in this field. The advantage of noble and precious metal is...

Copper-zirconia interfaces in UiO-66 enable selective catalytic hydrogenation of CO2 to methanol

Molecular interactions with both oxides and metals are essential for heterogenous catalysis, leading to remarkable synergistic impacts on activity and selectivity. Here, we show that the direct link between the two phases (and not merely being together) is required to selectively hydrogenate CO2 to methanol on catalysts containing Cu and ZrO2. Materials consisting of isolated Cu particles or atomically dispersed Cu–O–Zr sites only catalyze the reverse water-gas shift reaction. In contrast, a metal organic framework structure (UiO-66) with Cu nanoparticles occupying missing-linker defects maximizes the fraction of metallic Cu interfaced to ZrO2 nodes leading to a material with high adsorption capacity for CO2 and high activity and selectivity for low-temperature methanol synthesis.

A Novel Series of Single-Cluster Catalysts: Transition Metal Trimer Clusters Supported on Graphdiyne

<p>While single-atom catalysts (SACs) have achieved great success in the past decade, their application is potentially limited by the simplistic single-atom active centers, which makes single-cluster catalysts (SCCs) a natural extension. SCCs with precise numbers of atoms and structural configurations possess SAC’s merits, yet have greater potentials for catalyzing complex reactions and/or bulky reactants. Through systematic quantum-chemical studies and computational screening, we report here the rational design of transition metal trimer clusters anchored on graphdiyne as a novel kind of stable SCCs with great potentials for efficient and precise heterogenous catalysis. By investigating their structures and catalytic performance for oxygen reduction reaction, hydrogen evolution reaction, and CO₂ reduction reactions, we provide theoretical guidelines for their potential applications as heterogeneous catalysts. These graphdiyne supported SCCs provide an ideal benchmark scaffold for rational design of precise catalysts for industrially important chemical reactions. </p>