Design and Synthesis of Powerful Capsule Catalysts Aimed at Applications in C1 Chemistry and Biomass Conversion

Coaxial 3D Printing of Zeolite-Based Core-Shell Monolithic Cu-SSZ-13@SiO2 Catalysts for Diesel Exhaust Treatment

Core-shell catalysts with functional shells can increase the activity and stability of the catalysts in selective catalytic reduction of NOx with ammoniax. However, the conventional approaches based on multistep fabrication for core-shell structures encounter persistent restrictions regarding strict synthesis conditions and limited design flexibility. Herein, a facile coaxial 3D printing strategy is for the first time developed to construct zeolite-based core-shell monolithic catalysts with interconnected honeycomb structures, in which the hydrophilic noncompact silica serves as shell and Cu-SSZ-13 zeolite acts as core. Compared to a Cu-SSZ-13 monolith which suffers from the interfacial diffusion, the SiO2 shell layer can increase the accessibility of active sites over Cu-SSZ-13@SiO2, resulting in a 10-20% higher NO conversion at200-550 °C under 300 000 cm3 g-1 h-1. Meanwhile, a thicker SiO2 shell enhances the hydrothermal stability of the aged catalyst by inhibiting the dealumination and the formation of CuOx. Other representative monolithic catalysts with different topological zeolites as shell and diverse metal oxides as the core can be also realized by this coaxial 3D printing. This strategy allows multiple porous materials to be directly integrated, which allows for flexible design and fabrication of various core-shell monolithic catalysts with customized functionalities.

Synthesis and Application of Task-Specific Bimetal-Organic Frameworks in the Synthesis of Biological Active Spiro-Oxindoles

The use of click chemistry as a smart and suitable method for the development of new heterogeneous catalysts is based on metal-organic frameworks as well as the production of organic compounds. The development of the click chemistry method can provide a new strategy to achieve superior properties of MOFs. Here, the two metals Co and Fe are used to create a bimetallic-organic framework. In the following, the click chemistry and postmodification method are well organized and an acidic heterogeneous porous catalyst is developed. This prepared catalyst was used as a highly efficient catalyst for the preparation of new spiro-oxindoles obtained through click chemistry with good to excellent yields (80-94%). This presented catalytic system can compete with the best reported catalytic systems. The findings showed that the presence of Co and Fe metals in the MOF, and the presence of the triazole ring on the catalyst, can increase the catalytic efficiencies. This study offers novel insights into the architecture of Metal-Organic Frameworks (MOFs), click chemistry, and biologically active compounds. Additionally, the research explores the antibacterial properties of the synthesized spiro-oxindoles and catalysts. The findings reveal significant antibacterial activities of the synthesized compounds against S. aureus, MRSA, and E. coli bacteria.

Clever Nanomaterials Fabrication Techniques Encounter Sustainable C1 Catalysis

ConspectusC1 catalysis, which refers to the conversion of molecules with a single carbon atom, such as CO, CO2, and CH4, into clean fuels and basic building blocks for chemical industries, has built a bridge between carbon resource utilization and valuable chemical supply. With respect to the goal of carbon neutrality, C1 catalysis also plays an essential role owing to its integrated functions in the green catalytic process with fewer CO2 emissions and even direct high-value-added utilization of greenhouse gases (CO2 and CH4). However, the inert nature of the C-O or C-H bond in C1 molecules as well as uncontrollable C-C coupling render C1 catalysis challenging. The rational design of highly active catalytic materials (denoted as C1 catalysts) with strong capacities for C-O or C-H bond activation and C-C coupling by convenient nanomaterials fabrication methods to boost the catalytic performance of C1 molecule conversion, including targeted product selectivity and long-term stability, is the cornerstone of C1 catalysis.Notably, the familiar concepts in heterogeneous catalysis, such as tandem catalysis and confinement catalysis, are applicable for C1 catalysis and have been successfully used to design a C1 catalyst. Regarding the tandem catalysis concept that integrates multiple reactions in a single-pass via a bi- or multifunctional catalyst, it is promising to shed new light on the oriented conversion of C1 molecules, especially for C2+ hydrocarbon or oxygenate synthesis. The confinement effect is powerful for controlling the product distribution and enhancing activation efficiency of inert chemical bonds in C1 catalysis due to the unique reactants/intermediate adsorption and evolution behaviors on the confined catalytic interface with a special electronic environment. Moreover, metal-support interactions (MSIs), electronic properties of the active site, and catalytic engineering issues are also susceptible to the C1 molecule conversion performance. Therefore, under the guidance of basic and novel rules in heterogeneous catalysis, the innovation of catalytic materials with the aid of advanced catalytic materials fabrication techniques has always been a hot research topic in C1 catalysis.In this Account, we briefly describe the challenges in thermal-catalytic C1 molecule (mainly CO, CO2, and CH4) conversion. At the same time, the synergistic functioning of the physicochemical properties of the catalytic materials on the performance in C1 molecule conversion is highlighted. More importantly, we summarize our progress in rationally designing tailor-made C1 catalysts to enhance C1 molecule activation efficiency and targeted product selectivity via powerful nanomaterials fabrication techniques, such as traditional wet-chemistry strategies, the magnetron sputtering method, and 3D printing technology. Specifically, the ingenious capsule catalyst and ammonia pools in zeolites fabricated by a wet chemistry process possess an extraordinary effect on the transformation of CO, CO2, and CH4 molecules. Also, the sputtering method is reliable in modulating the electronic properties of metallic active sites for C1 molecule conversion, thereby tailoring the final product selectivity. Furthermore, we showcase the strong capability of metal 3D printing technology in fabricating a self-catalytic reactor, by which the functions of the reaction field and nanoscale active sites are well integrated. Finally, we predict the future research opportunities in highly efficient C1 catalyst design with the assistance of clever nanomaterials fabrication techniques.

Advanced zeolite and ordered mesoporous silica-based catalysts for the conversion of CO2 to chemicals and fuels

For many years, capturing, storing or sequestering CO₂ from concentrated emission sources or from air has been a powerful technique for reducing atmospheric CO₂. Moreover, the use of CO₂ as a C1 building block to mitigate CO₂ emissions and, at the same time, produce sustainable chemicals or fuels is a challenging and promising alternative to meet global demand for chemicals and energy. Hence, the chemical incorporation and conversion of CO₂ into valuable chemicals has received much attention in the last decade, since CO₂ is an abundant, inexpensive, nontoxic, nonflammable, and renewable one-carbon building block. Nevertheless, CO₂ is the most oxidized form of carbon, thermodynamically the most stable form and kinetically inert. Consequently, the chemical conversion of CO₂ requires highly reactive, rich-energy substrates, highly stable products to be formed or harder reaction conditions. The use of catalysts constitutes an important tool in the development of sustainable chemistry, since catalysts increase the rate of the reaction without modifying the overall standard Gibbs energy in the reaction. Therefore, special attention has been paid to catalysis, and in particular to heterogeneous catalysis because of its environmentally friendly and recyclable nature attributed to simple separation and recovery, as well as its applicability to continuous reactor operations. Focusing on heterogeneous catalysts, we decided to center on zeolite and ordered mesoporous materials due to their high thermal and chemical stability and versatility, which make them good candidates for the design and development of catalysts for CO₂ conversion. In the present review, we analyze the state of the art in the last 25 years and the potential opportunities for using zeolite and OMS (ordered mesoporous silica) based materials to convert CO₂ into valuable chemicals essential for our daily lives and fuels, and to pave the way towards reducing carbon footprint. In this review, we have compiled, to the best of our knowledge, the different reactions involving catalysts based on zeolites and OMS to convert CO₂ into cyclic and dialkyl carbonates, acyclic carbamates, 2-oxazolidones, carboxylic acids, methanol, dimethylether, methane, higher alcohols (C₂₊OH), C₂₊ (gasoline, olefins and aromatics), syngas (RWGS, dry reforming of methane and alcohols), olefins (oxidative dehydrogenation of alkanes) and simple fuels by photoreduction. The use of advanced zeolite and OMS-based materials, and the development of new processes and technologies should provide a new impulse to boost the conversion of CO₂ into chemicals and fuels.

Direct Synthesis of Dimethyl Ether from CO2: Recent Advances in Bifunctional/Hybrid Catalytic Systems

Dimethyl ether (DME) is a versatile raw material and an interesting alternative fuel that can be produced by the catalytic direct hydrogenation of CO2. Recently, this process has attracted the attention of the industry due to the environmental benefits of CO2 elimination from the atmosphere and its lower operating costs with respect to the classical, two-step synthesis of DME from syngas (CO + H2). However, due to kinetics and thermodynamic limits, the direct use of CO2 as raw material for DME production requires the development of more effective catalysts. In this context, the objective of this review is to present the latest progress achieved in the synthesis of bifunctional/hybrid catalytic systems for the CO2-to-DME process. For catalyst design, this process is challenging because it should combine metal and acid functionalities in the same catalyst, in a correct ratio and with controlled interaction. The metal catalyst is needed for the activation and transformation of the stable CO2 molecules into methanol, whereas the acid catalyst is needed to dehydrate the methanol into DME. Recent developments in the catalyst design have been discussed and analyzed in this review, presenting the different strategies employed for the preparation of novel bifunctional catalysts (physical/mechanical mixing) and hybrid catalysts (co-precipitation, impregnation, etc.) with improved efficiency toward DME formation. Finally, an outline of future prospects for the research and development of efficient bi-functional/hybrid catalytic systems will be presented.

Engineering well-defined rare earth oxide-based nanostructures for catalyzing C1 chemical reactions

In this review, we summarize the nanostructural engineering and applications of rare earth oxide-based nanomaterials with well-defined compositions, crystal phases and shapes for efficiently catalyzing C1 chemical reactions.

Iodide/H₂O₂ Catalyzed Intramolecular Oxidative Amination for the Synthesis of 3,2'-Pyrrolidinyl Spirooxindoles

An ammonium iodide/hydrogen peroxide-mediated intramolecular oxidative amination of 3-aminoalkyl-2-oxindoles was achieved, affording the corresponding 3,2'-pyrrolidinyl spirooxindoles and their 6- or 7-membered analogous in moderate to high yields. This metal-free procedure features very mild reaction conditions, non-toxicity and easily handled hydrogen peroxide as a clean oxidant.

Preparation of Ruthenium Dithiolene Complex/Polysiloxane Films and Their Responses to CO Gas

To develop advanced materials using metal complexes, it is better to prepare metal complexes contained in composite or hybrid films. To achieve this purpose, we synthesized ruthenium complexes with dihalogen-substituted benzendithiolate ligands, [(η⁶-C₆Me₆)Ru(S₂C₆H₂X₂)] (X = F, 3,6-Cl, Br, 4,5-Cl), 1b-1e. We also investigated preparation of 1c or 1e containing polysiloxane composite films and their reactivity to CO gas. All ruthenium complexes 1b-1e reacted with CO gas, and carbonyl ligand adducts 2b-2e were generated. Ruthenium complexes 1b-1e show two strong absorption peaks around 550 and 420 nm. After exposure to CO gas, these absorption peaks were immediately decreased without a peak shift. A similar trend was observed in 1c or 1e containing polysiloxane composite films. These results indicate that 1c and 1e were easily converted into 2c and 2e, both in the solution and the polysiloxane film during CO gas exposure.