Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Chemical Reviews, Год журнала: 2022, Номер 123(9), С. 6039 - 6106

Опубликована: Сен. 1, 2022

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, nanoparticles in the framework-associated sites extra-framework positions, thus affording metal-in-zeolite catalysts outstanding activity, unique shape selectivity, enhanced recyclability processes of Brønsted acid-, Lewis metal-catalyzed reactions. Especially, thanks to advances zeolite synthesis characterization techniques recent years, zeolite-confined (denoted as metal@zeolite composites) have experienced rapid development heterogeneous catalysis, owing combination merits both intrinsic properties. In this review, we will present developments strategies incorporating tailoring zeolites advanced identification location, distribution, coordination environment species zeolites. Furthermore, catalytic applications demonstrated, emphasis on composites hydrogenation, dehydrogenation, oxidation Finally, point out current challenges future perspectives precise synthesis, atomic level identification, practical application catalyst system.

Язык: Английский

---

Methane Oxidation to Methanol

Chemical Reviews, Год журнала: 2022, Номер 123(9), С. 6359 - 6411

Опубликована: Дек. 2, 2022

The direct transformation of methane to methanol remains a significant challenge for operation at larger scale. Central this is the low reactivity conditions that can facilitate product recovery. This review discusses issue through examination several promising routes and an evaluation performance targets are required develop process We explore methods currently used, emergence active heterogeneous catalysts their design reaction mechanisms provide critical perspective on future operation. Initial experiments discussed where identification gas phase radical chemistry limited further development by approach. Subsequently, new class catalytic materials based natural systems such as iron or copper containing zeolites were explored milder conditions. key issues these technologies conversion often overoxidation products. Despite this, interest high in wider appeal effective route products from C–H activation, particularly with need transition net carbon zero renewable sources exciting.

Язык: Английский

---

In Situ UV–Vis–NIR Absorption Spectroscopy and Catalysis

Chemical Reviews, Год журнала: 2024, Номер 124(5), С. 2352 - 2418

Опубликована: Фев. 26, 2024

This review highlights

Язык: Английский

---

Synthesis, characterization and application of Fe-zeolite: A review

Applied Catalysis A General, Год журнала: 2021, Номер 630, С. 118467 - 118467

Опубликована: Дек. 18, 2021

Язык: Английский

---

Interconversion of Atomically Dispersed Platinum Cations and Platinum Clusters in Zeolite ZSM-5 and Formation of Platinum gem-Dicarbonyls

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(30), С. 13874 - 13887

Опубликована: Июль 19, 2022

Catalysts composed of platinum dispersed on zeolite supports are widely applied in industry, and coking sintering during operation under reactive conditions require their oxidative regeneration, with the cycling between clusters cations. The intermediate species have remained only incompletely understood. Here, we report an experimental theoretical investigation structure, bonding, local environment cationic ZSM-5, which key intermediates this cycling. Upon exposure to O2 at 700 °C, fragmentation occurs, Pt2+ ions stabilized six-membered rings that contain paired aluminum sites. When exposed CO mild conditions, these form highly uniform gem-dicarbonyls, can be converted H2 Ptδ+ monocarbonyls. This conversion, weakens platinum-zeolite is a first step toward migration aggregation into clusters. X-ray absorption infrared spectra provide evidence reductive transformations various gas environments. chemistry general, as shown by observation gem-dicarbonyls several commercially used zeolites (ZSM-5, Beta, mordenite, Y).

Язык: Английский

---

Zinc-indium-sulfide favors efficient C − H bond activation by concerted proton-coupled electron transfer

Nature Communications, Год журнала: 2024, Номер 15(1)

Опубликована: Июнь 11, 2024

Abstract C − H bond activation is a ubiquitous reaction that remains major challenge in chemistry. Although semiconductor-based photocatalysis promising, the mechanism elusive. Herein, we report value-added coupling products from wide variety of biomass and fossil-derived reagents, formed via over zinc-indium-sulfides (Zn-In-S). Contrary to commonly accepted stepwise electron-proton transfer pathway (PE-ET) for semiconductors, our experimental theoretical studies evidence concerted proton-coupled electron (CPET) pathway. A pioneering microkinetic study, considering relevant elementary steps surface chemistry, reveals faster with Zn-In-S because circumventing formation charged radical, as it happens PE-ET where retards catalysis due strong site adsorption. For CPET Zn-In-S, abstraction, forming neutral rate-limiting, but having lower energy barriers than PE-ET. The rate expressions derived microkinetics provide guidelines rationally design semiconductor catalysis, e.g., activation, based on mechanism.

Язык: Английский

---

Second-Sphere Lattice Effects in Copper and Iron Zeolite Catalysis

Chemical Reviews, Год журнала: 2022, Номер 122(14), С. 12207 - 12243

Опубликована: Янв. 25, 2022

Transition-metal-exchanged zeolites perform remarkable chemical reactions from low-temperature methane to methanol oxidation selective reduction of NOx pollutants. As with metalloenzymes, metallozeolites have impressive reactivities that are controlled in part by interactions outside the immediate coordination sphere. These second-sphere effects include activating a metal site through enforcing an "entatic" state, controlling binding and access pockets channels, directing radical rebound vs cage escape. This review explores these emphasis placed on but not limited focus copper iron active sites, although other transition-metal-ion zeolite also explored. While actual active-site geometric electronic structures different compared their lattice or protein environments found strong parallels contribute high activity selectivity.

Язык: Английский

---

Structure of Selective and Nonselective Dicopper (II) Sites in CuMFI for Methane Oxidation to Methanol

ACS Catalysis, Год журнала: 2022, Номер 12(24), С. 15626 - 15637

Опубликована: Дек. 6, 2022

The one-step valorization of natural gas remains a challenge. Methane conversion to methanol via chemical looping over copper-containing zeolites is promising route, and CuMFI among the earliest successfully applied. However, structure active sites in CuMFI, as well effect copper loading Si/Al ratio on speciation, are yet be understood. We found that for Cu/Al determines selectivity methane by governing dicopper sites. At below 0.3, MFI materials host dimeric centers with Cu–Cu separation 2.9 Å UV/vis absorption band at 27 200 cm–1 capable selective oxidation wide temperature range (450–550 K). A higher leads formation mono-μ-oxo = 3.2 Å, which exhibit characteristic 21 900 react lower temperatures (<450 K), yielding overoxidation products. Identifying distinctions nonselective will aid design better-performing materials.

Язык: Английский

---

Evolution of Framework Al Arrangements in CHA Zeolites during Crystallization in the Presence of Organic and Inorganic Structure-Directing Agents

Crystal Growth & Design, Год журнала: 2022, Номер 22(10), С. 6275 - 6295

Опубликована: Сен. 19, 2022

The arrangement of Al heteroatoms in zeolite frameworks influences turnover rates Brønsted acid-catalyzed reactions and the speciation exchanged metal cations complexes that are active sites for redox catalysis. substitution Si generates anionic lattice charges is thus influenced by structure charge density cationic directing agents (SDAs) guide crystallization. Here, we investigate how framework arrangements chabazite (CHA) zeolites evolve as a function hydrothermal treatment time amorphous precursors convert into partially fully crystalline aluminosilicate phases presence organic inorganic SDAs. With N,N,N-trimethyl-1-adamantylammonium (TMAda+) sole SDA, an network initially forms contains large fraction proximal sites, quantified Co2+ titration, which evolves CHA crystallites contain high six-membered rings (6-MR). After bulk crystallization has been completed (433 K, 36 h), continued causes rearrangement to become more site-isolated, eventually resulting with undetectable numbers 6-MR paired 144 h). These temporal changes indicate Si–O–Al linkages remain labile undergo restructuring within domains under conditions, allowing atomic toward thermodynamically preferred distributions (e.g., isolated TMAda+ only). Ab initio molecular dynamics (AIMD) simulations report configurations be lower energy than pair field TMAda+, supporting thermodynamic driving force isolate when SDA. In contrast, using both Na+ co-SDAs did not result any further after was complete 96 suggesting co-occlusion suppresses lability bonds phases. AIMD charge-balanced TMAda+. findings can upon extended from such evolution factors, extending prior reports phenomena occurring during interzeolite conversion routes.

Язык: Английский

---

Self-adjusted reaction pathway enables efficient oxidation of aromatic C–H bonds over zeolite-encaged single-site cobalt catalyst

CHINESE JOURNAL OF CATALYSIS (CHINESE VERSION), Год журнала: 2024, Номер 57, С. 133 - 142

Опубликована: Фев. 1, 2024

Язык: Английский

---