The reactivity of tetracarbonylnickel encapsulated in zeolite X. A case history of intrazeolite coordination chemistry

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.

Embedding lanthanide-functionalized polymers into hollow mesoporous silica spheres: a ship-in-a-bottle approach to luminescent hybrid materials

Using hollow mesoporous silica spheres (HMSS) as host (“bottle”) and 4-vinylpyridine (4VP), Ln(iii) chlorides (Ln = Eu, Tb), and 1,10-phenanthroline (Phen) as “ship” components gives facile access to luminescent hybrid materials.

Site isolated complexes of late transition metals grafted on silica: challenges and chances for synthesis and catalysis

Grafting, quo vadis? The reasons for the aggregation of late transition metal complexes on oxide supports under reducing conditions and/or in the presence of π-accepting ligands are discussed, and strategies are suggested to prevent it.

Zeolite Mediated Reactions: Mechanistic Aspects and Environmental Applications

An overview is presented of basic research and applications for the use of zeolites in environmentally-related topics. The use of these materials to promote oxidation reactions, and other catalytic processes is surveyed along with ship-in-a-bottle synthesis of particular zeolite-encapsulated catalysts. Methods for probing the surfaces of zeolites using spin-probes and ESR detection are mentioned. The ability of some thermally activated zeolites to produce spontaneously radical cations by single-electron oxidation of organic molecules is reviewed. The issue of the degree of acidity of H-zeolites is discussed, which demonstrates them not to be super-acids. Some ESR determinations of the adsorption of NOx species onto selected zeolites are reviewed and the use of zeolites to catalyse desulfurisation of hydrocarbons is considered. Finally, there is mention made of the use of zeolites to catalyse hydrodechlorination of CFC's and other organic chlorine-containing compounds. Surfactant-modified zeolites (SMZ) for use as polyfunctional decontamination agents are further discussed. Theoretical methods, e.g. Density Functional Theory (DFT), are finding their own application to studying the mechanisms of reactions that are mediated by zeolites as is shown throughout.

A supramolecular "ship in bottle" strategy for enantiomeric selectivity in geminate radical pair recombination

[reaction: see text] Reactions in which zeolites are modified with chiral inductors to serve as media for chiral induction are often limited by the propensity of both substrate and inductor to occupy the same supercage. Herein, we report a "ship in bottle" strategy utilizing the thermal decomposition of dioxetanes obtained from oxazolidinone-substituted enecarbamates for the enantioselective generation of methyl desoxybenzoin (MDB). Photoexcitation of the supramolecular geminate molecular pair results in enrichment of the opposite enantiomer of MDB.