Wei Chen

Optimizing syntheses of known zeolite structures and exploring novel applications for them are enduring priorities in zeolite chemistry. A representative example is the AFI zeolite framework, which features one‐dimensional 12‐membered‐ring channels but remains difficult to synthesize directly in its aluminosilicate form because of the lack of suitable organic templates. Herein, with the assistance of theoretical simulations for the design of novel organic templates, we have been successful in the one‐pot synthesis of aluminosilicate AFI structure designated as ZJM‐12, giving the nanocrystals with a size of approximately 20 nm. Characterization results revealed that the ZJM‐12 zeolite exhibited high crystallinity, nanoscale crystal dimension, large specific surface area, fully 4‐coordinated Al species, abundant acid sites, and good hydrothermal stability. In the catalytic tests for the conversion of lactic acid (LA) to lactide (LT) and the intramolecular cyclization of 5‐(o‐tolyl)‐2‐pentene (OTP) to 1,5‐dimethyltetralin (1,5‐DMT), the ZJM‐12 zeolite displayed excellent catalytic performance compared with conventional catalysts used for these reactions, thus highlighting its considerable potential as a high‐performance catalyst for the above conversion processes.

AEI topology molecular sieves (MAPO-18) have shown promising properties as components of OX-ZEO type tandem catalysts, where the Brønsted acid sites (BAS) introduced by different framework substitutions lead to distinct catalytic mechanisms on the CO2-to-hydrocarbons conversion. Ketenes are key intermediates in the conversion of methanol to hydrocarbons. This study provides molecular-level insights into the reactions of three ketenes (ketene, methyl ketene, and dimethyl ketene) with the BAS in MAPO-18 (M = Si, Mg) molecular sieves at operando conditions through first-principles molecular dynamics (FPMD) simulations combined with enhanced sampling techniques. Free energy surfaces constructed from FPMD simulations revealed distinct kinetic and thermodynamic preferences, linking them to different reaction routes for the production of olefins. Prior studies suggested that ketenes and their protonated analogues are key intermediates in two different pathways to olefins formation, and the three ketenes exhibited higher kinetic stability than their protonated forms in H-SAPO-18 compared to H-MgAPO-18, suggesting a high tendency for olefin production via the (cyclo)addition-decarboxylation route in H-SAPO-18. In contrast, the increased stability of the cationic intermediates and low protonation barrier for methyl and dimethyl ketenes in MgAPO-18 favor their direct decarbonylation to olefins. Surface-bound species displayed decreasing stability from surface acetate to surface propionate to surface isobutyrate , aligning with established trends for surface alkoxides. Moreover, a comparison with static calculations demonstrates their limited ability to capture the entropic contributions and dynamic effects that dominate the behavior of active intermediates under realistic reaction conditions, highlighting the necessity of molecular dynamics (MD) approaches for accurate mechanistic modeling of catalytic reactions. Benchmarking against high-level random phase approximation (RPA) calculations further revealed that the density functional theory (DFT) method in combination with the revPBE-D3 functional used in the FPMD simulations may overestimate the stability of cationic intermediates and underestimate the protonation barriers of ketene. Together, these findings underscore the importance of combining dynamic simulations with accurate potential energy descriptions to reliably model active intermediates in confined microporous environments. Overall, this study provides key steps of ketene reactivity in zeolite frameworks, bridging computational and experimental insights into CO2-to-hydrocarbon conversion pathways. These results emphasize how subtle variations in the framework composition and substituents dictate the reaction mechanisms, offering guidance for the rational design of molecular sieves tailored for selective catalytic transformations.

We show the need for quantum-accurate dynamics across scales within catalysis and explore machine learning potentials for reaction–diffusion modelling.

The ubiquitous presence of water vapor represents a critical challenge for the practical implementation of metal-organic frameworks (MOFs). Although the water stability of some MOFs has been studied, existing stability tests were rarely conducted under industrial relevant dynamic conditions. We therefore systematically compared the water stability of commercially available α-Mg₃(HCOO)₆ MOF and isostructural α-M₃(HCOO)₆ (M = Mn, Co, Ni) MOFs. All MOFs rapidly transformed to dense M(HCOO)₂·2H₂O when in contact with liquid water. The transformation is considerably slower in water vapor, following a stability order of Ni > Mg ≈ Co > Mn. Notably, activated MOFs exhibited higher stability than as-made MOFs under dynamic water vapor flow, while their stabilities are comparable under static water vapor. We conclude that such hydrolysis stability enhancement is due to the kinetic effect: weakly adsorbed water molecules are rapidly removed in dynamic vapor flow when channels are open, resulting in delayed hydrolysis. These findings show that even MOFs, which are thermodynamically prone to hydrolysis, can retain their functionality in dynamic vapor flow, providing valuable guidance for the industrial application of MOFs.

Zeolite-catalyzed methanol-to-hydrocarbon conversion is a promising technology for the sustainable production of valuable hydrocarbon products. However, the mechanism behind the formation of the first carbon-carbon bond has been a subject of controversy for several decades. By comprehensive consideration of previous experimental phenomena and theoretical studies, a formaldehyde (HCHO)-based first carbon-carbon formation mechanism is proposed. Within the new mechanism, hydrated or methylated products of HCHO (methanediol, methyloxymethanol, and dimethyloxymethane) with much weaker C-H bond strengths replace methane in the traditional methane-HCHO mechanism, allowing energetically and kinetically favorable pathways to form the first C-C bond. The formed C-C bond products are further converted to ketene and olefins via the methylation-decarbonylation route. The plausibility of the newly proposed mechanism is confirmed by both theoretical calculations and experiments in various MTH zeolite catalysts. A key intermediate in this mechanism is glycolaldehyde, which was captured in situ by both mass spectrometry and Fourier transform infrared spectroscopy. The viability of the mechanism in different zeolites, as predicted theoretically, was also confirmed by gas chromatography. Not only does this new mechanism introduce an innovative pathway for the first C-C bond formation, but it also provides a comprehensive explanation of the specific role of HCHO in the early stage of the MTH process and associated reactions.

Deconstructive transformation of carbon-carbon double bonds (C=C) is a pivotal strategy in synthetic chemistry and drug discovery. Despite the substantial advances in olefin metathesis and ozonolysis for natural product synthesis through C=C double-bond cleavage, the catalytic remodeling of complex molecules through C=C double-bond deconstruction has been underdeveloped. We report a heterogeneous copper-catalyzed C=C double-bond cleavage, which enables the remodeling of complex molecules by converting the carbons on either side of the C=C double bond to carbonyl and cyano groups, respectively. In particular, this method provides an efficient protocol to conveniently transform terpenoids, glycals, steroids, and bioactive molecules to privileged scaffolds with underexplored chemical space.

Compared to methanol, dimethyl ether (DME) is a more ideal and attractive raw material for industrial applications. Typically, the industrially zeolite-catalyzed methanol dehydration to DME occurs at temperatures above 423 kelvin. Improving catalytic reactivity and reducing energy consumption are urgently needed but remain challenging. Here, we report an unexplored associative strategy to realize DME formation at room temperature and the generation of olefins even at 413 kelvin, which is achieved by coinjecting basic acetone to manipulate the local chemical microenvironment of the methanol reactant inside the H-ZSM-5 zeolite. The crucial role of acetone in accelerating methanol direct dehydration to DME is highlighted as the obvious destabilization effect for the adsorbed methanol cluster with strong hydrogen bonds and the subsequent traction of water during DME formation. These findings offer more insights into the rational design of reaction systems by manipulating the local surroundings to regulate catalytic performances and should represent a large step forward in methanol conversion technology.

Metal-organic frameworks (MOFs) are a class of porous materials that are of topical interest for their utility in water-related applications. Nevertheless, molecular-level insight into water-MOF interactions and MOF hydrolytic reactivity remains understudied. Herein, we report two hydrolytic pathways leading to either structural stability or framework decomposition of a MOF (ZnMOF-1). The two distinct ZnMOF-1 water reaction pathways are linked to the diffusion rate of incorporated guest dimethylformamide (DMF) molecules: slow diffusion of DMF triggers evolution of the initial MOF into a water-stable MOF product exhibiting enhanced water adsorption, while fast exchange of DMF with water leads to decomposition. The starting MOF, three intermediates from the water reaction pathways and the final stable MOF have been characterized. The documentation of two distinct pathways counters the stereotype that water exposure always leads to destruction or degradation of water-sensitive MOFs, and demonstrates that water-stable MOFs with improved adsorption properties can be prepared via controlled solvent-triggered structural rearrangement.