Abstract
A series of gas‐phase reactants is used to treat a Cu‐exchanged mordenite zeolite with the aim of studying the influence of the reaction environment on the formation of Cu pairs. The rearrangement of Cu ions to form multimeric sites as a function of their oxidation state was probed by X‐ray absorption spectroscopy (XAS) and also by applying advanced analysis through wavelet transform, a method able to specifically locate Cu–Cu interactions also in the presence of overlapping contributions from other scattering paths. The nature of the Cu‐oxo species formed upon oxidation was further crosschecked by DFT‐assisted fitting of the EXAFS data and by resonant Raman spectroscopy. Altogether, the CuI/CuII speciation clearly correlates with Cu proximity, with metal ion pairs quantitatively forming under an oxidative environment.
Highlights
Within the paradigm of an improved use of fossil resources, strategies facilitating the exploitation of many small/remote natural gas sources is of utmost importance.[1,2] In particular, chemical processes able to transform methane into liquid analogues are desirable for a simplified handling and transportation
Angewandte Chemie International Edition published by Wiley-VCH GmbH
We focus on an ad hoc synthesized Cu-MOR (Si/a single Tfw (Al) = 8.22 and Cu/Al = 0.27, atomic ratios from EDX), Angew
Summary
Different reaction conditions heavily impact the speciation of Cu inside the zeolite framework, influencing DMTM.[10] Overall, the CuI/CuII redox cycle and the local coordination environment around Cu sites are the key features for understanding these complex systems. In this context, opportune gas-phase reactants (e.g. NH3) affect both Cu speciation and framework distribution when used prior to oxidation, as the coordinative nature of NH3 enhances the Cu cations mobility.[11] the Cu speciation in the framework changes,[12] as well as the average Cu–Cu distance, in turn conditioning the formation of active species. Through DFT-supported fitting of the EXAFS data, specific Cu-oxo species were identified
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