Meeting the growing global energy and commodity chemical demands necessitates the development of new, rationally designed materials. Of particular interest is the utilization of CO₂ as a precursor for value-added chemical feedstocks, owing to its abundance, low cost, and versatile chemistry. While numerous heterogeneous catalyst materials have been developed for the conversion of CO₂ into useful chemicals such as cyclic carbonates, they often require harsh conditions. Furthermore, fundamental understanding of the structural properties driving catalysis remains an ongoing challenge.
Catalytically active metal–organic frameworks (MOFs) are a promising solution for these challenges, due to their high porosity and molecular level synthetic control. The recent discovery of nonanuclear metal clusters-based HEMOFs with up to 15 different rare-earth elements demonstrated these materials are highly effective for the conversion of CO₂ into cyclic carbonates under mild conditions; however, the synergistic metal-metal interactions promoting activity were not fully optimized. Here, a series of HEMOFs constructed of five unique rare-earth elements were synthesized, systematically varying the fifth element composing the framework. This family of HEMOFs enabled the study of the impact of both specific metal identities and resulting intermetallic effects on their catalytic activity. Materials were extensively characterized through physical and spectroscopic methods, including powder X-ray diffraction, N₂ and CO₂ gas sorption, scanning electron microscopy, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy. Candidate materials were evaluated as catalysts for the conversion of CO₂into cyclic carbonates. Conversion was found to be directly tunable to the identity of the five metals chosen, with the high-entropy materials outcompeting their monometallic counterparts. This work highlights the importance of judicious choice of individual components within high-entropy materials to take advantage of unique synergistic effects.

This research was supported by the Laboratory Directed Research and Development Program at Sandia National Laboratories. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.

Caith McKeown

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