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Non-oxidative coupling of methane (NOCM) is a sought-after reaction that has been studied for decades. Harsh reaction conditions (T >800°C) in the face of limited catalyst stability lead to rapid catalyst deactivation and strong coking, preventing application thus far. Recent reports have shown the significance of an interplay of catalyst nature and reaction conditions, whereas metal carbides have prevailed to play a crucial role which involves incorporation of carbidic carbon in C2Hx and aromatic products. This perspective gives an overview of proposed mechanistic pathways and considerations about experiment conditions in order to foster a rational catalyst design platform for NOCM.

The Catalysis Hub – Swiss CAT+ is a new infrastructure project funded by ETH-domain, co-headed by EPFL and ETHZ. It offers the scientific community a unique integrated technology platform combining automated and high-throughput experimentation with advanced computational data analysis to accelerate the discoveries in the field of sustainable catalytic technologies. Divided into two hubs of expertise, homogeneous catalysis at EPFL and heterogeneous catalysis at ETHZ, the platform is open to academic and private research groups. Following a multi-year investment plan, both hubs have acquired and developed several high-end robotic platforms devoted to the synthesis, characterization, and testing of large numbers of molecular and solid catalysts. The hardware is associated with a fully digitalized experimental workflow and a specific data management strategy to support closed-loop experimentation and advanced computational data analysis.

The combination of high-throughput experimentation (HTE) and data analysis is a valuable methodology for mechanistic interrogation and rational development of catalysts. In this article, we point out the general structure of HTE-data analysis workflow and illustrate how it can be applied with examples of olefin metathesis and cyanation reactions.

The selective partial oxidation of methane to methanol remains a great challenge in the field of catalysis. Cu-exchanged zeolites are promising materials, directly and selectively converting methane to methanol with high yield under cyclic conditions. However, the economic viability of these aluminosilicate materials for potential industrial applications remains a challenge. Exploring copper supported on non-microporous oxide supports and rationalising the structure/reactivity relationships extends the scope of material investigation and opens new possibilities. Recently, copper on alumina was demonstrated to be active and selective for the partial oxidation of methane. This work aims to explore the formation of well-defined Cu(II) oxo species on silica via surface organometallic chemistry and examines their reactivity for the selective transformation of methane to methanol. Isolated Cu(II) sites were generated via grafting of a tailored molecular precursor. Activation under oxidative conditions and subsequent removal of organic moieties from the grafted copper centres led to the formation of small copper (II) oxide clusters, which are active in the partial oxidation of methane under mild conditions, albeit significantly less efficient than the corresponding isolated Cu(II) sites on alumina.

Spectator oxo ligands are ubiquitous in catalysis, in particular in olefin epoxidation and olefin metathesis. Here we use computationally derived 17O NMR parameters to probe the electronic structure of spectator oxo ligands in these two reactions. We show that 17O NMR parameters allow to distinguish between doubly-bonded and triply-bonded oxo ligands, giving detailed insights into the frontier molecular orbitals involved in the metaloxo bonds along the reaction pathway. On the one hand, our study shows that in olefin epoxidation catalysed by methyltrioxorhenium (MTO), the oxo ligand significantly changes its bonding mode upon formation of the oxygen-transferring Re-oxo-bisperoxo-species, changing its nature from a doubly bonded to a triply bonded oxo ligand. On the other hand, only minor changes in the binding mode are found along the olefin metathesis reaction pathway with Mo- and W-based oxo-alkylidene species, in which the oxo ligand behaves as a triply bonded ligand throughout the reaction. This finding contrasts earlier studies that proposed that the change of binding mode of the oxo ligand was key to metallacyclobutane formation.

Chemical shift tensors give valuable insights into the nature and the relative energy of frontier orbitals and their analysis allows for rationalizing the reactivities of molecules. In this article, we point out the principles that allow for the analysis of chemical shift. Through selected, illustrative examples we show how one can relate chemical shift to molecular electronic structure and thus to reactivity.

The conversion of CO2 to more valuable chemicals has been the focus of intense research over the past decades, and this field has become particularly important in view of the continuous increase of CO2 levels in our atmosphere and the need to find alternative ways to store excess energy into fuels. In this review we will discuss different strategies for CO2 conversion with heterogeneous and homogeneous catalysts. In addition, we will introduce some promising research concerning the immobilization of homogeneous catalysts on heterogeneous supports, as a hybrid of hetero- and homogeneous catalysts.

Heterogeneous catalysis is essential for the transformation of light hydrocarbons into chemical feedstocks. Many of the catalysts that mediate these transformations consist of isolated metal ions on the surface of a metal oxide support, such as silica or alumina. Due to the complexity of these catalysts, studying the active site and mechanism of these reactions is difficult. Surface organometallic chemistry (SOMC) could offer a solution to this problem by allowing the synthesis of well-defined surface organometallic species. This approach has been used to study the reactions of light hydrocarbons with isolated metal species on silica and alumina surfaces. These studies showed that proton transfers play a key role in the reactions of many hydrocarbons. The mechanisms of these reactions and their role in some common catalytic cycles are discussed.

Solid-state NMR plays a critical role in establishing the atomic structure of surface species, obtained by the controlled grafting of organometallic complexes onto amorphous oxide supports, a promising strategy towards molecularly defined heterogeneous catalysts. Using one-dimensional or multi-dimensional NMR analysis allows us to map the structure of organometallic residues on surfaces, in a similar fashion that the structure of homogeneous catalysts can be determined using solution NMR techniques. In addition, chemical shift anisotropy analysis can be used as a tool to obtain detail structures and to determine the dynamics of surface species. In combination with DFT calculations we have also shown that the structure of aluminum species can be determined using high-field and ultrafast 27Al NMR. Finally, we discussed the latest development in Dynamic Nuclear Polarization, which allows the selective enhancements of the NMR signals of surface species, thus reducing the NMR acquisition time by factors up to 10,000. This makes solid-state NMR an indispensible tool in determining structure-property relationship and in the development of advanced materials including catalysts through more rational approach.

Based on a molecular approach combining controlled surface chemistry, advanced spectroscopic methods, in particular solid-state NMR, and computational chemistry, it is possible to develop single-site species and to control the growth of nanoparticles on supports. This allows the generation of highly efficient catalysts combining the advantages of both homogeneous and heterogeneous catalysts and function materials with defined properties.