Kvantově-chemické studium adsorpce v mikroporézních materiálech

Microporous materials play a crucial role in a wide range of applications in chemical engineering, chemistry, material science or lately even in medicine. Zeolites and metal- organic frameworks (MOFs) take a prominent place among them. The most important fields of applications include gas separation, purification or gas storage. A detailed understanding of adsorption properties of these materials represents a long-standing effort from experimental as well as computational chemistry community. However, ac- curate computational description of adsorption in microporous materials represents a significant challenge for computational chemists as: (i) unit cells of the crystalline mi- croporous materials are typically large, (ii) dispersion interactions are of importance, and (iii) there are metal cations, often with open-shell electronic structure, present in the framework interacting strongly and specifically with adsorbing molecules. Despite a significant progress made in theoretical description of adsorption mechanisms in both zeolites and MOFs in last decade, there is a number of applications and systems for which the commonly used computational approaches fail to provide a needed accuracy. A whole class of such systems is represented, for example, by MOFs containing tran- sition metal coordinatively...Mikroporézní materiály hrají významnou roli v mnoha oblastech aplikace chemického inženýrství, chemie, materiálového výzkumu a v poslední době dokonce i v oblasti medicíny. Nejvýznamnější z nich jsou zeolity a mikroporézní koordinační polymery (angl. Metal Organic Frameworks, zkráceně MOF), které se používají především k rozdělování plynů, jejich čištění a k jejich uskladňování. Dlouhodobým cílem expe- rimentálních a výpočetních chemiků je pochopit mechanismus adsorpce v těchto ma- teriálech. Nicméně přesný popis tohoto procesu představuje velkou výzvu, protože (i) jednotkové cely krystalických forem těchto materiálů jsou obvykle velké, (ii) disperzní interakce musí být zohledněny, (iii) ve struktuře jsou přítomny kationty kovů, často s otevřenou elektronovou slupkou, které interagují silně a specificky s adsorbujícími se molekulami. Přes významný pokrok v teoretickém popisu mechanismu adsorpce v ze- olitech a MOFech zaznamenaný v posledních letech, stále zůstává množství aplikací a systémů, pro které obecně používané výpočetní přístupy selhávají. Příkladem celé třídy takovýchto systému jsou MOFy obsahující v adsorpčních místech přechodné kovy, které jsou koordinačně...Department of Physical and Macromolecular ChemistryKatedra fyzikální a makromol. chemieFaculty of SciencePřírodovědecká fakult

A reactive neural network framework for water-loaded acidic zeolites

Under operating conditions, the dynamics of water and ions confined within protonic aluminosilicate zeolite (H-AS) micropores are responsible for many of their properties, including hydrothermal stability, acidity and catalytic activity. However, due to high computational cost, operando studies of H-AS are currently rare and limited to specific cases and simplified models. In this work, we have developed a general potential energy surface interpolator with consistent accuracy for the entire class of H-AS, including the full range of experimentally relevant water concentrations and Si/Al ratios, via a reactive neural network potential (NNP). This NNP combines dramatic sampling acceleration at the metaGGA reference level with the capacity for discovery of new chemistry, such as collective defect formation mechanisms at the zeolite surface. Furthermore, we show that the baseline model allows for data-efficient adoption of higher-level (hybrid) references via $\Delta$-learning and the acceleration of rare event sampling via automatic construction of collective variables. This framework allows for operando simulations of realistic catalysts at quantitative accuracy.Comment: Supplementary information adde

Teoretické stueium kyselých zeolitů

The acidic zeolite H-FER with Si:Al ratios of 71, 35 and 8 was investigated employing a periodic DFT model, as well as cluster models and the CCSD(T) level of theory. The computational study of the H- FER in a high silica form (Si:Al = 71) accompanied by the investigation of the interaction of the CO and N2 probe molecules with the H-FER sample was supplemented with the experimental data obtained from the variable temperature infrared spectroscopy (VTIR). The H-FER samples with different Si:Al ratios were characterized by the structure, location and relative stabilities of the Brønsted acid groups. Relative stability of these sites was found to be dependent on Si:Al ratio, which is the main factor dictating the relative concentration of Brønsted acid sites having different types of local configuration. The number of AlO4 tetrahedra sharing an oxygen with the SiO4 tetrahedron involved in the Brønsted acid site determines the Si-O(H)-Al angle, O-H stretching frequency and deprotonation energy (and hence acid strength). Furthermore, the theoretical results obtained for the CO and N2 interaction with the H-FER were found to be in a good agreement with the experimental VTIR data. Several types of hydrogen-bonded OH···CO and OH···N2 complexes were characterized, formed by interaction between the adsorbed...Byla provedena studie kyselých zeolitů H-FER s Si:Al poměrem 71, 35 a 8 pomocí periodického DFT modelu, klastrového modelu a také pomocí CCSD(T) metody. Výpočetní studie zeolitu H-FER ve vysokosilikátové formě (Si:Al=71) společně s výzkumem interakce CO a N2 (testovacích molekul) s H- FER byly doplněny experimentálními daty pořízenými infračervenou spektroskopií při různé teplotě (VTR). U vzorků H-FER s různým poměrem Si:Al byla popsaná struktura, umístění a relativní stabilita jejich kyselých Brønstedových skupin. Bylo zjištěno, že relativní stabilita jednotlivých vazebných míst je závislá na poměru Si:Al, který je také hlavním faktorem určujícím relativní koncentraci kyselých Brønstedových vazebných míst s různými typy lokální konfigurace. Počet AlO4 tetraedrů sdílejících kyslíkový atom s SiO4 tetraedrem obsahujícím kyselé Brønstedové vazebné místo určuje Si-O(H)-Al úhel, O-H stretch frekvenci a deprotonizační energii (a z ní vyplývající kyselost). Bylo navíc zjištěno, že teoretické výsledky vztahující se k CO a N2 interakci s H-FER zeolitem jsou v dobré shodě s experimentálními VTIR daty. Bylo popsáno několik typů vodíkově vázaných komplexů OH...CO a OH...N2 vznikajících na základě interakce mezi absorbovanými molekulami a kyselými Brønstedovými OH skupinami zeolitu. Ze studie vyplývá, že CO a...Department of Physical and Macromolecular ChemistryKatedra fyzikální a makromol. chemieFaculty of SciencePřírodovědecká fakult

Quantum-chemical study of adsorption in microporous materials

Microporous materials play a crucial role in a wide range of applications in chemical engineering, chemistry, material science or lately even in medicine. Zeolites and metal- organic frameworks (MOFs) take a prominent place among them. The most important fields of applications include gas separation, purification or gas storage. A detailed understanding of adsorption properties of these materials represents a long-standing effort from experimental as well as computational chemistry community. However, ac- curate computational description of adsorption in microporous materials represents a significant challenge for computational chemists as: (i) unit cells of the crystalline mi- croporous materials are typically large, (ii) dispersion interactions are of importance, and (iii) there are metal cations, often with open-shell electronic structure, present in the framework interacting strongly and specifically with adsorbing molecules. Despite a significant progress made in theoretical description of adsorption mechanisms in both zeolites and MOFs in last decade, there is a number of applications and systems for which the commonly used computational approaches fail to provide a needed accuracy. A whole class of such systems is represented, for example, by MOFs containing tran- sition metal coordinatively..

Teoretické studium kyselých zeolitů

The acidic zeolite H-FER with Si:Al ratios of 71, 35 and 8 was investigated employing a periodic DFT model, as well as cluster models and the CCSD(T) level of theory. The computational study of the H- FER in a high silica form (Si:Al = 71) accompanied by the investigation of the interaction of the CO and N2 probe molecules with the H-FER sample was supplemented with the experimental data obtained from the variable temperature infrared spectroscopy (VTIR). The H-FER samples with different Si:Al ratios were characterized by the structure, location and relative stabilities of the Brønsted acid groups. Relative stability of these sites was found to be dependent on Si:Al ratio, which is the main factor dictating the relative concentration of Brønsted acid sites having different types of local configuration. The number of AlO4 tetrahedra sharing an oxygen with the SiO4 tetrahedron involved in the Brønsted acid site determines the Si-O(H)-Al angle, O-H stretching frequency and deprotonation energy (and hence acid strength). Furthermore, the theoretical results obtained for the CO and N2 interaction with the H-FER were found to be in a good agreement with the experimental VTIR data. Several types of hydrogen-bonded OH···CO and OH···N2 complexes were characterized, formed by interaction between the adsorbed..

Ověření spolehlivosti metody DFT pro popis elektronicky vzbuzených stavů iontů mědi

Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Quantifying the effect of Si/Al ratio on proton solvation and water diffusion in H-FAU using reactive neural network potential.

Acidic zeolites are one of the most important catalysts. In many of their catalytic applications, the mode of interaction with water heavily influences their activity, efficiency, and durability as a catalyst. Despite the recent (first principles) computational efforts to understand the mechanistic underpinning of the water-zeolite interactions, it is still prohibitively expensive to carry out comprehensive studies employing realistic zeolitic models. Therefore, we used a recently developed reactive neural network-based potential for aluminosilicate zeolites in the protonic form including their interaction with the aqueous solution that has a capacity to accelerate simulation by orders of magnitude while retaining the reference level of accuracy. We used it to determine how multiple factors (aluminum content, water loading and temperature) influence the proton solvation and water dynamics in one of the industrially most important acidic zeolites, the faujasite (FAU). We found that Si/Al ratio is a significant determinant of the water diffusivity, water capacity to solvate protons in the nanopores, and the zeolite hydrolytic stability. We expect that many of these findings are readily extendable to other acidic zeolites in interaction with water