Together with group of Prof. Dirk de Vos, our team gets a new multidisciplinary project on Pd- and Ru- catalysts18.12.2019
As the result of a collaborative work between our Institute and Prof. Dirk de Vos group from KU Leuven, our project "Rational design of Pd-catalysts for C-H activation and Ru-catalysts for C=O hydrogenation: from operando X-ray absorption spectroscopy identification of metal complexes to multi-technique machine learning-based characterization" is supported by the joint RSF-FWO grant for 3 years. Only 11 projects were supported within this call.
The new project is aimed to develop a method based on machine learning (ML) for quantitative analysis of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and Fourier-transform infrared (FTIR) spectra. Combination of these spectroscopies allows descripting both the structure of the catalytically active metal center and adsorbed organic species. The main challenge of the analysis of such data for real catalytic systems is the dynamic evolution of active metal sites along the reaction, so that their structures may not correspond to any known reference structures from the crystallographic databases. For the unknown structures, comparison with theoretically calculated spectra is, in principle possible, but requires (especially for XANES and FTIR spectra) utilization of hypothetical structures with huge number of variable parameters. For such multiparametric problem, ML algorithms are highly appropriate. However, the application of ML for analysis for X-ray absorption spectra have been shown only recently by few research groups [4,5], including the team of this project . Thus, development of sustainable algorithms and its further delivery as a user-friendly software to the scientific community will become a considerable and innovative achievement in the field of material science. Moreover, unlike the existing methods in quantitative spectroscopy, our algorithm will perform simultaneous analysis of three different spectral regions, which will improve stability and precision of the obtained results. We will establish a database of theoretical XANES and FTIR spectra, describing more than 15000 of different coordinations of Pd- and Ru-complexes in different charge state, train ML algorithm and further apply it to real experimental data.
The developed algorithms will be applied to determine fundamental structure-reactivity relationships in two industrially relevant reactions: Ru-catalyzed selective deoxygenation of polyols to olefins and Pd-catalyzed, dehydrogenative coupling of arene C-H bonds to olefinic C-H bonds resulting in the creation of new C-C bonds, for which Leuven group has designed a new class of heterogeneous catalysts . We will develop a specialized operando cell for measurements of solid and liquid samples under pressures up to 20 bar. Operando experiments will be performed using synchrotron radiation sources, including the leading European synchrotron source – ESRF, which undergoes upgrade program and will be reopened for users in 2020. To identify both active and inactive species we aim to explore wide ranges of experimental conditions and sample types. Then, applying multivariate statistical methods we will decompose the whole experimental dataset into the spectra of “pure” states of metal complexes and their concentration profiles, which will be correlated to the reaction products monitored by means of online mass spectrometry and infrared spectroscopy, while the structure of the corresponding metal sites will be determined using ML algorithms according to the calculated spectral database.
Finally, based on the obtained structure-reactivity relationships, we will develop new catalytic materials with improved properties. In particular, for Ru-catalyst for hydrogenative deoxygenation of erythritol, we aim for a TON number ≥ 500 and a selectivity of at least 85 % for butenes. And for Pd-catalysts for arene C-H activation, we will improve its resistance towards deactivation, resulting in overall 2-3 times increase of TON and positional selectivity over 75% in the activation of C-H bonds on the arene ring. This materials will act as prototypes for real catalysis for fine chemical and pharmaceutical industries. Thus, within this project we will be solving both fundamental and methodological problems, as well as developing new materials for practical applications.