Traditional heterogeneous catalysis is constrained by kinetic and thermodynamic limits, such as the Sabatier principle and reaction equilibrium. Dynamic and resonant catalysts hold promise to overcome these limitations by actively oscillating a catalyst’s physical or electronic structure at the time scale of the catalytic cycle, allowing programmable control over reaction pathways, and leading to improved rate and selectivity. External stimuli such as temperature swing, mechanical strain, electric charge, and light can perturb catalyst surfaces in different ways, altering adsorbate coverage, binding energies, and transition states beyond what steady-state catalysis allows. This work surveys the current state of dynamic catalysis, introduces the concept of “stimulando” characterization for observing transient dynamics, and outlines key modeling, mechanistic, and benchmarking strategies to advance the field toward improved chemical transformation.

The Gutmann–Beckett method involves the reaction of a phosphine oxide with a Lewis acid, followed by measurement of the change in ³¹P NMR chemical shift (Δδ) relative to the free phosphine oxide. This is the most commonly used experimental method to assess Lewis acid strength in solution and on solid materials containing Lewis acid sites. This study describes the origin of the ³¹P NMR Δδ deshielding that occurs in triethylphosphine oxide (TEPO) adducts of Lewis acids. 57 Lewis acid adducts were studied using DFT methods. These models span typical three-, four-, and five-coordinate Lewis acids as well as models that approximate the coordination sphere of Lewis acid sites proposed to be present in heterogeneous materials. When a TEPO···Lewis acid adduct forms, electron density from the oxygen is transferred to the Lewis acid, which reduces the negative hyperconjugation from the oxygen to the σ*_P–C that weakens the P═O bond. Experimental and DFT studies show that the ³¹P NMR chemical shift deshields in TEPO···Lewis adducts because the most shielded δ₃₃ component of the chemical shift tensor shifts dramatically downfield. This deshielding is correlated with the weakening of the P═O bond. Natural chemical shift (NCS) analysis shows that δ₃₃ deshielding in Lewis acid adducts is due to coupling of the filled σ_P–C with the empty π*_P═O, the LUMO of the TEPO fragment. This study connects the ³¹P NMR chemical shift, in particular the experimentally observable Δδ₃₃, to P═O bond weakening. Thus, the Gutmann–Beckett method does not provide information on adduct formation energy, the more typically sought measure of Lewis acidity, but rather provides a different thermodynamic descriptor of Lewis acid strength in the weakening of the P═O bond.

Chemical recycling of polyolefins represented by polyethylene (PE) and polypropylene (PP) via catalytic cracking has emerged as a promising strategy for converting waste plastics into valuable hydrocarbons. In this study, we investigated the selective hydrocracking of PP into light alkanes (C₁–C₅) using zeolite catalysts at 280 °C under 1 MPa H₂. An HMFI zeolite with high Al content exhibited the best catalytic performance among various zeolite catalysts tested. In situ DRIFTS comparing bare HMFI and externally-silylated HMFI suggested that the external surface Brønsted acid sites serve as the active sites for the cracking of PP. Combination of in situ DRIFTS and UV–vis spectroscopy analyses identified the formation and consumption of oligomeric species as a reaction intermediate during reaction. Density functional theory (DFT) calculations suggested that a route in which the carbocation and alkoxide intermediates generated by hydrocracking of PP undergo low-energy barrier transformations into gaseous products such as C₃ and C₄ hydrocarbons. This study advances the development of sustainable polyolefin recycling technologies.

This chapter provides a brief introduction to computational chemistry in the context of zeolite research, emphasizing the capabilities and limitations of modern theoretical models for investigating their reactivity and chemical properties under operando conditions. A brief overview of the computational chemistry toolbox is given, followed by a discussion of state-of-the-art applications in zeolite chemistry and catalysis. This chapter also highlights the increasing impact of data-driven techniques, such as machine-learning potentials, in advancing computational methods in zeolite studies.

Cu-modified zeolites provide methane conversion to methanol with high selectivity under mild conditions. The activity of different Cu-sites for methane transformation is still under discussion. Herein, ZSM-5 zeolite has been loaded with Cu²⁺ cations (1.4 wt % Cu) as characterized by UV-vis DRS, EPR, EXAFS, and ¹H MAS NMR. It is inferred that Cu²⁺ cations, attached to the cation-exchange Al−O⁻−Si sites of the zeolite framework, can exist in the form of either isolated or paired Cu²⁺ sites. The transformation of methane to methanol on Cu²⁺/H-ZSM-5 has been verified by the observation of the methoxy species formation with ¹³C MAS NMR and FTIR spectroscopy. The related mechanisms have been analyzed by DFT calculations. The calculations show that the paired Cu²⁺ sites enable heterolytic C−H bond dissociation via the “alkyl” pathway resulting in methylcopper species, which however are not detected experimentally due to further rapid transformation to surface methoxy species through methyl radical formation and recombination with Si−O⁻Al site. Based on the obtained data, it has been concluded that methane transformation to methanol on paired Cu²⁺ sites, having no extra-framework oxygen ligand, is possible in Cu-modified zeolites. The pathways of Cu²⁺ cations regeneration with O₂ and H₂O have been experimentally explored.

Organic electrochemistry is currently experiencing an era of renaissance, which is closely related to the possibility of carrying out organic transformations under mild conditions, with high selectivity, high yields, and without the use of toxic solvents. Combination of organic electrochemistry with alternative approaches, such as photo-chemistry was found to have great potential due to induced synergy effects. In this work, we propose for the first time utilization of plasmon triggering of enhanced and regio-controlled organic chemical transformation performed in photoelectrochemical regime. The advantages of the proposed route is demonstrated in the model amination reaction with formation of C−N bond between pyrazole and substituted benzene derivatives. Amination was performed in photo-electrochemical mode on the surface of plasmon active Au@Pt electrode with attention focused on the impact of plasmon triggering on the reaction efficiency and regio-selectivity. The ability to enhance the reaction rate significantly and to tune products regio-selectivity is demonstrated. We also performed density functional theory calculations to inquire about the reaction mechanism and potentially explain the plasmon contribution to electrochemical reaction rate and regioselectivity.

Rational plastic recycling is critical for addressing the environmental challenges associated with plastic waste. Among the various recycling methods, chemical recycling, particularly via homogeneous catalysis, holds promise for converting plastic waste into valuable products. Post-consumer polymer wastes could present a challenge for catalytic upcycling due to the structural inhomogeneity and functionalization of the polyolefin chains. The impact of substrate aging on the performance of the upcycling catalyst can be viewed as an “inverse problem” of heterogeneous catalysis and has not received sufficient attention in mechanistic studies on this subject. Herein, we present a density functional theory study on the dehydrogenative upcycling of polyethylene (PE) with different in-chain impurities, representing the chemistry of post-consumption PE wastes. We selected the (^tBu4POCOP)-Ir pincer complex catalyzed dehydrogenation of PE as our model reaction. The calculations reveal that common in-chain impurities found in PE, such as carbonyl, hydroxyl, epoxides, and chlorine atoms, inhibit the overall catalyst performance. These impurities form stable molecular complexes with the catalyst, leading to a substantial increase in the energy barriers of the initial reaction step, the C-H bond addition. We also observe that the reaction on the ideal crystalline PE is also impeded. However, highly distorted PE chains exhibit greater susceptibility toward the (^tBu4POCOP)-Ir catalyst. Our mechanistic studies demonstrated that the reaction on the side alkane chains is kinetically favorable compared with the reaction on the PE backbone. The study highlights the critical role of in-chain heterogenieties in the catalytic activation of polymer chains and provides valuable insights into the development of effective technologies for upcycling plastic waste.

The stoichiometric conversion of methane to methanol by Cu-exchanged zeolites can be brought to highest yields by the presence of extraframework Al and high CH₄ chemical potentials. Combining theory and experiments, the differences in chemical reactivity of monometallic Cu-oxo and bimetallic Cu-Al-oxo nanoclusters stabilized in zeolite mordenite (MOR) are investigated. Cu-L₃ edge X-ray absorption near-edge structure (XANES), infrared (IR), and ultraviolet-visible (UV-vis) spectroscopies, in combination with CH₄ oxidation activity tests, support the presence of two types of active clusters in MOR and allow quantification of the relative proportions of each type in dependence of the Cu concentration. Ab initio molecular dynamics (MD) calculations and thermodynamic analyses indicate that the superior performance of materials enriched in Cu-Al-oxo clusters is related to the activity of two μ-oxo bridges in the cluster. Replacing H₂O with ethanol in the product extraction step led to the formation of ethyl methyl ether, expanding this way the applicability of these materials for the activation and functionalization of CH₄. We show that competition between different ion-exchanged metal-oxo structures during the synthesis of Cu-exchanged zeolites determines the formation of active species, and this provides guidelines for the synthesis of highly active materials for CH₄ activation and functionalization.

The reactivity theories and characterization studies for metal-containing zeolites are often focused on probing the metal sites. We present a detailed computational study of the reactivity of Zn-modified BEA zeolite towards C-H bond activation of the methane molecule as a model system that highlights the importance of representing the active site as the whole reactive ensemble integrating the extra-framework Zn_EF²⁺ cations, framework oxygens (O_F²⁻), and the confined space of the zeolite pores. We demonstrate that for our model system the relationship between the Lewis acidity, defined by the probe molecule adsorption energy, and the activation energy for methane C-H bond cleavage performs with a determination coefficient R² = 0.55. This suggests that the acid properties of the localized extra-framework cations can be used only for a rough assessment of the reactivity of the cations in the metal-containing zeolites. In turn, studying the relationship between the activation energy and pyrrole adsorption energy revealed a correlation, with R² = 0.80. This observation was accounted for by the similarity between the local geometries of the pyrrole adsorption complexes and the transition states for methane C-H bond cleavage. The inclusion of a simple descriptor for zeolite local confinement allows transferability of the obtained property-activity relations to other zeolite topologies. Our results demonstrate that the representation of the metal cationic species as a synergistically cooperating active site ensembles allows reliable detection of the relationship between the acid properties and reactivity of the metal cation in zeolite materials.

Selective dimerization of ethene to 2-butene on Zn2+-containing ZSM-5 zeolite (Zn2+/ZSM-5) at 296-523 K has been discovered. The intermediate but-3-en-1-ylzinc species is identified with 13C CP/MAS NMR and Fourier transform infrared spectroscopy. The density functional theory study of two alternative dimerization pathways reveals that the intermediate is formed with the involvement of the saturated bridged dimeric Zn-(CH2)4-O species. It is also shown that ethene conversion to 2-butene increases with the increase in the quantity of Brønsted acid sites in Zn2+/ZSM-5 zeolite; however, the selectivity of the reaction decreases. The results obtained are of potential interest for developing industrially relevant Zn-containing zeolite catalysts for the selective conversion of ethene to 2-butene.

The intermediates formed upon the interaction of methane with Cu-modified ZSM-5 zeolites (Cu/H-ZSM-5) have been analyzed with solid-state NMR spectroscopy and DFT methods. Methane activation by Cu/H-ZSM-5 zeolites gives rise to three distinct surface methoxy-like species (-O-CH₃) detected by ¹³C MAS NMR spectroscopy with specific chemical shifts in the range of 53-63 ppm. DFT calculations on representative cluster models of different sites potentially present in Cu/H-ZSM-5 have been used to assign these signals to (i) methanol adsorbed on two neighboring Cu sites (Cu-(HOCH₃)-Cu, 62.6 ppm), (ii) methanol adsorbed on zeolite Brønsted acid sites (52.9 ppm), and (iii) lattice-bound methoxy groups (Si-O(CH₃)-Al, 58.6). The formation of these methoxy-like intermediates depends on the Cu loading and, accordingly, the type of Cu species in the Cu/H-ZSM-5 zeolite. For the sample with low (0.1 wt %) Cu loading containing exclusively mononuclear isolated Cu species, only the intermediates ii and iii have been detected. The Cu-bound intermediate (i) is formed upon methane activation by multinuclear Cu sites featuring Cu-O-Cu bridging moieties present in the materials with relatively higher Cu loading (1.38 wt %). The presented results indicate that methane activation by Cu/H-ZSM-5 can be promoted by both mono- and multinuclear Cu species confined in the zeolite matrix.

The influence of the model and method choice on the DFT predicted 13C NMR chemical shifts of zeolite surface methoxide species has been systematically analyzed. Twelve 13C NMR chemical shift calculation protocols on full periodic and hybrid periodic-cluster DFT calculations with varied structural relaxation procedures are examined. The primary assessment of the accuracy of the computational protocols has been carried out for the Si-O(CH3)-Al surface methoxide species in ZSM-5 zeolite with well-defined experimental NMR parameters (chemical shift, δ(13C) value) as a reference. Different configurations of these surface intermediates and their location inside the ZSM-5 pores are considered explicitly. The predicted δ value deviates by up to ±0.8 ppm from the experimental value of 59 ppm due to the varied confinement of the methoxide species at different zeolite sites (model accuracy). The choice of the exchange-correlation functional (method accuracy) introduces ±1.5 ppm uncertainty in the computed chemical shifts. The accuracy of the predicted 13C NMR chemical shifts for the computational assignment of spectral characteristics of zeolite intermediates has been further analyzed by considering the potential intermediate species formed upon methane activation by Cu/ZSM-5 zeolite. The presence of Cu species in the vicinity of surface methoxide increases the prediction uncertainty to ±2.5 ppm. The full geometry relaxation of the local environment of an active site at an appropriate level of theory is critical to ensure a good agreement between the experimental and computed NMR data. Chemical shifts (δ) calculated via full geometry relaxation of a cluster model of a relevant portion of the zeolite lattice site are in the best agreement with the experimental values. Our analysis indicates that the full geometry optimization of a cluster model at the PBE0-D3/6-311G(d,p) level of theory followed by GIAO/PBE0-D3/aug-cc-pVDZ calculations is the most suitable approach for the calculation of 13C chemical shifts of zeolite surface intermediates.