Robust Polymer-Coated Diamond Supports for Noble-Metal Nanoparticle Catalysts

Polymer Coated Functional Catalysts for Industrial Applications

Surface engineering of conventional catalysts using polymeric coating has been extensively explored for producing hybrid catalytic material with enhanced activity, high mechanical and thermal stability, enhanced productivity, and selectivity of the desired product. The present review discusses in detail the state-of-the-art knowledge on surface modification of catalysts, namely photocatalysts, electrocatalysts, catalysts for photoelectrochemical reactions, and catalysts for other types of reactions, such as hydrodesulfurization, carbon dioxide cycloaddition, and noble metal-catalyzed oxidation/reduction reactions. The various techniques employed for the polymer coating of catalysts are discussed and the role of polymers in enhancing the catalytic activity is critically analyzed. The review further discusses the applications of biodegradable and biocompatible natural polysaccharide-based polymers, namely, chitosan and polydopamine as prospective coating material.

Heterometallic multinuclear nodes directing MOF electronic behavior

Metal node engineering in combination with modularity, topological diversity, and porosity of metal–organic frameworks (MOFs) could advance energy and optoelectronic sectors. In this study, we focus on MOFs with multinuclear heterometallic nodes for establishing metal−property trends, i.e., connecting atomic scale changes with macroscopic material properties by utilization of inductively coupled plasma mass spectrometry, conductivity measurements, X-ray photoelectron and diffuse reflectance spectroscopies, and density functional theory calculations. The results of Bader charge analysis and studies employing the Voronoi–Dirichlet partition of crystal structures are also presented. As an example of frameworks with different nodal arrangements, we have chosen MOFs with mononuclear, binuclear, and pentanuclear nodes, primarily consisting of first-row transition metals, that are incorporated in HHTP-, BTC-, and NIP-systems, respectively (HHTP³⁻ = triphenylene-2,3,6,7,10,11-hexaone; BTC³⁻ = 1,3,5-benzenetricarboxylate; and NIP²⁻ = 5-nitroisophthalate). Through probing framework electronic profiles, we demonstrate structure–property relationships, and also highlight the necessity for both comprehensive analysis of trends in metal properties, and novel avenues for preparation of heterometallic multinuclear isoreticular structures, which are critical components for on-demand tailoring of properties in heterometallic systems.

Metal node engineering in combination with modularity, topological diversity, and porosity of metal–organic frameworks (MOFs) could advance energy and optoelectronic sectors.

Pd Nanoparticle-Decorated 3D-Printed Hierarchically Porous TiO2 Scaffolds for the Efficient Reduction of a Highly Concentrated 4-Nitrophenol Solution

The large amount of 4-nitrophenol (4-NP) wastewater produced by the chemical industry has received increased concern over the growing risk of environmental pollution. The ability to catalyze the reduction of highly concentrated 4-NP wastewater is highly desirable for the practical treatment of industrial wastewater, yet it remains a significant challenge. Herein, we report Pd nanoparticle-decorated 3D-printed hierarchically porous TiO₂ scaffolds (Pd/TiO₂ scaffolds) for the efficient reduction of highly concentrated 4-NP wastewater (2 g·L^-1, ∼14.38 mM). The millimeter-sized interconnected channels in the scaffolds are conducive to rapid mass and ion transportation; meanwhile, the abundant micrometer- and nanometer-sized pores on the surface of the scaffolds offer adequate anchoring sites for Pd nanoparticles. The turnover frequency of the hierarchically porous Pd/TiO₂ scaffold (16 layers) is up to 2.69 min^-1, which is 1063 times higher than that of the Pd/TiO₂-bulk material with the same size (0.00253 min^-1). Importantly, no obvious deactivation of the catalytic activity is observed even after 20 cycles of catalytic reduction of 4-NP, showing excellent catalytic stability and reusability. Our strategy of loading the nanostructured catalyst on 3D-printable hierarchically porous structures put forward a flexible and versatile approach for boosting the catalytic performance of the catalysts, including catalytic activity, stability, and reusability, which can help promote their practical application in industry.

Facile fabrication of bimetallic Cu–Ag binary hybrid nanoparticles and their application in catalysis

Herein, high efficiency and recyclable Cu–Ag hybrid catalyst (Trp–Cu–Ag) NPs were prepared by the hydrothermal method using l-tryptophan as a reducing agent and protecting reagent.

Multifunctional Surface Modification of Nanodiamonds Based on Dopamine Polymerization

Surface functionalization of nanodiamonds (NDs), which is of great interest in advanced material and therapeutic applications, requires the immobilization of functional species, such as nucleic acids, bioprobes, drugs, and metal nanoparticles, onto NDs' surfaces to form stable nanoconjugates. However, it is still challenging to modify the surface of NDs due to the complexity of their surface chemistry and the low density of each functional group on the surfaces of NDs. In this work, we demonstrate a general applicable surface functionalization approach for the preparation of ND-based core-shell nanoconjugates using dopamine polymerization. By taking advantage of the universal adhesion and versatile reactivity of polydopamine, we have effectively conjugated DNA and silver nanoparticles onto NDs. Moreover, the catalytic activity of ND-supported silver nanoparticle was characterized by the reduction of 4-nitrophenol, and the addressability of NDs was tested through DNA hybridization that formed satellite ND-gold nanorod conjugation. This simple and robust method we have presented may significantly improve the capability for attaching various functionalities onto NDs and open up new platforms for applications of NDs.

Simple surface-assisted formation of palladium nanoparticles on polystyrene microspheres and their application in catalysis

Herein we develop a facile and green method for assembling palladium nanoparticles on polystyrene microsphere with excellent catalytic performance.

Catalytic Reduction of 4-Nitrophenol: A Quantitative Assessment of the Role of Dissolved Oxygen in Determining the Induction Time

The reduction of 4-nitrophenol to 4-aminophenol by borohydride is one of the foremost model catalytic reactions because it allows for a straightforward assessment of catalysts using the kinetic parameters extracted from the real-time spectroscopic monitoring of an aqueous solution. Crucial to its standing as a model reaction is a comprehensive mechanistic framework able to explain the entire time evolution of the reaction. While much of this framework is in place, there is still much debate over the cause of the induction period, an initial time interval where no reaction seemingly occurs. Here, we report on the simultaneous monitoring of the spectroscopic signal and the dissolved oxygen content within the aqueous solution. It reveals that the induction period is the time interval required for the level of dissolved oxygen to fall below a critical value that is dependent upon whether Au, Ag, or Pd nanoparticles are used as the catalyst. With this understanding, we are able to exert complete control over the induction period, being able to eliminate it, extend it indefinitely, or even induce multiple induction periods over the course of a single reaction. Moreover, we have determined that the reaction product, 4-aminophenol, in the presence of the same catalyst reacts with dissolved oxygen to form 4-nitrophenolate. The implication of these results is that the induction period relates, not to some activation of the catalyst, but to a time interval where the reaction product is being rapidly transformed back into a reactant by a side reaction.