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Death and Life of Catalysts: a Theory-Guided Unified Approach for Non-Critical Metal Catalyst Development

Periodic Reporting for period 4 - DeLiCAT (Death and Life of Catalysts: a Theory-Guided Unified Approach for Non-Critical Metal Catalyst Development)

Reporting period: 2020-09-01 to 2022-04-30

Catalysis plays a pivotal role in all strategies towards sustainable chemical technologies of the future. To minimize the adverse effects due to the use of non-renewable hydrocarbon feedstocks, new technologies are necessary to make the existing chemical processes more atom and energy- efficient and enable the transition to renewable feedstocks. Endeavors towards the sustainable use of feedstocks should be accompanied by the efforts to make the catalyst utilization also more sustainable. DeLiCAT aimed at introducing an integrated computational and experimental strategy for the design and optimization of efficient catalytic systems based on non-critical metal-based catalysts for green chemical and clean energy conversions.

DeLiCAT key hypothesis is that the catalytic function critically depend on the conditions of the chemical transformation. Practical catalyst systems are highly complex, multicomponent, and intrinsically multifunctional. Their performance critically depend on a wide range of parameters such as the activation procedure, the presence of promotors, type of the support or reaction solvent, and the reaction conditions (T, p, medium composition). The position within such a complex parameter space defines the preference of the catalytic species to live and promote the desirable chemical transformation or die via one of the competing deactivation channels. DeLiCAT specifically focused on understanding and addressing the issue of catalyst deactivation limiting the utility of non-noble metal-based catalysts in practical applications. To achieve this, DeLiCAT has put forward an innovative workflow integrating advanced experimental and computational methodologies an efficient knowledge exchange loop. New methods for automated reaction network analysis and operando modeling and characterization of complex catalytic systems were developed to understand how variation in the reaction conditions affects the behavior of the catalyst system. These insights guided the experiments through the highly complex and multidimensional condition space to achieve unprecedented catalyst lifetime and efficiency. Catalyst deactivation is inevitable. However, DeLiCAT demonstrated that one can postpone it through the rational optimization of the catalyst system and, hence, improve its performance so that a higher yield of desirable products could be produced with lower catalyst concentration and a higher efficiency.

Our work provides an essential fundamental basis and practical strategies for the design of new more efficient catalytic technologies for sustainable chemical and energy conversions. The resulting innovative technological solutions are key to addressing the most pressing societal challenges of today such as the climate change mitigation, protection of the environment and establishment of a truly circular economy for the future generations.
DeLiCAT involved cross-disciplinary research efforts of experimental and computational scientists supported by a broad network of research collaborations with international leaders in chemistry and catalysis.

The experimental part of DeLiCat was primarily devoted to the synthesis and investigation of new Mn-based catalysts for selective reduction transformations. The special focus was on addressing the issue of catalyst deactivation as the key factor limiting their utility in synthetic applications. We developed a broad family of Mn-catalysts active in carbonyl reduction. Ligand motifs included bidentate CN, PN, NN architectures (with N-heterocyclic carbene (NHC), phosphine and amine donors) and CNC, CNP, CNN pincers. The catalytic behavior of these complexes has been investigated thoroughly. To facilitate this, new operando spectroscopy and high-resolution kinetic analysis methodologies were developed. In addition to deep mechanistic insights, we discovered new catalytic chemistries previously unknown for Mn catalysts, namely, the C=C bond transposition and alkoxycarbonylation. The understanding of the deactivation mechanisms guided the development of a new dynamic Mn-CNP system with an exceptional resistance to deactivation and unprecedented catalytic performance.

The second pillar of DeLiCat was the development of new operando modeling approaches for automated computational analysis of reaction networks and prediction of plausible reacton/deactivation channels. Here both homogeneous and heterogeneous catalysis were considered. The model homogeneous catalyst systems were directly related to the parallel experimental program. The mechanistic strategies and computational tools for modeling reactive ensembles and condition-dependent behavior in heterogeneous catalysts have been developed with model systems representing zeolite-based cooperative catalysts and oxide-supported transition metal catalysts. The main activities within the theoretical part of the project were devoted to i) the development of new methods for studying conditions dependencies in reactive multicomponent solutions, ii) establishing hierarchical operando multiscale models for complex cooperative catalytic systems, and (iii) computational chemistry automation to eliminate the expert-bias in mechanistic analysis and enable high-throughput computational catalyst screening. An innovative computational strategy enabling the automated exploration of deactivation reaction paths and targeted screening of catalyst libraries has been successfully developed.

By using the new operando modelling approaches we demonstrated that the deactivation paths can be controlled not only by structural modification of catalyst but, innovatively, by modifying the secondary parameters of the catalytic systems. This new theoretical concept has been extended to heterogeneous catalysis. Advanced experimentation and operando spectroscopy studies have been carried out to confirm the predicted intrinsic condition-dependency of fundamental thermodynamic constants in complex catalytic systems and put forward a new theory of the role of promotors in liquid phase catalytic transformations.

The DeLiCAT research has led to 37 peer-reviewed publications and 2 successfully defended PhD thesis (3 more PhD thesis and at least 6 more publications will be completed in a near future). Several publications were reported in high-impact top-level journals. The results of the project were exchanged and communicated to the broad research audience via various topical and general chemistry conferences as well as dedicated lectures at companies and universities.
DeLiCAT has produced unprecedented new insights into the impact of the reaction environment and operation conditions on the fundamental reactivity parameters of realistic catalyst systems, which are important for rational design of new catalytic technologies for sustainable chemical conversions.
Automated computational chemistry strategies for screening catalyst space
From understanding deactivation to unprecedented catalyst performance
Expert bias-free approach to address active site structures in heterogeneous catalysis