Thermal Defect Engineering of Precious Group Metal–Organic Frameworks: A Case Study on Ru/Rh-HKUST-1 Analogues
Werner R. Heinz, Iker Agirrezabal-Tellería, Raphael Junk, Jan Berger, Junjun Wang, Dmitry Sharapa, Miryam Gil-Calvo, Ignacio Luz, Mustapha Soukri, Felix Studt, Yuemin Wang, Christof Wöll, Hana Bunzen, Markus Drees, Roland A. Fischer
Abstract
] (HKUST-1; BTC = 1,3,5-benzenetricarboxylate). Quantitative monitoring of the TDE process and extensive characterization of the samples employing a complementary set of analytical and spectroscopic techniques reveal that the compositionally very complex TDE-MOF materials result from the elimination and/or fragmentation of ancillary ligands and/or linkers. TDE involves the preferential secession of acetate ligands, intrinsically introduced via coordination modulation during synthesis, and the gradual decarboxylation of ligator sites of the framework linker BTC. Both processes lead to modified Ru/Rh paddlewheel nodes. These nodes exhibit a lowered average oxidation state and more accessible open metal centers, as deduced from surface-ligand IR spectroscopy using CO as a probe and supported by density functional theory (DFT)-based computations. The monometallic and the mixed-metal PGM-MOFs systematically differ in their TDE properties and, in particular in the hydride generation ability (HGA). This latter property is an important indicator for the catalytic activity of PGM-MOFs, as demonstrated by the ethylene dimerization reaction to 1-butene.