Activation of Methane by Rhodium Clusters on a Model Support C₂₀H₁₀

Abstract

Supported metals represent an important family of catalysts for the transformation of the most stable alkane, methane, under mild conditions. Here, using state-of-the-art mass spectrometry coupled with a newly designed double ion trap reactor that can run at high temperatures, we successfully immobilize a series of Rh n − (n = 4−8) cluster anions on a model support C 20 H 10 . Reactivity measurements at room temperature identify a significantly enhanced performance of large-sized Rh 7,8 C 20 H 10 − toward methane activation compared to that of free Rh 7,8 − . The "support" acting as an "electron sponge" is emphasized as the key factor to improve the reactivity of large-sized clusters, for which the high electron-withdrawing capability of C 20 H 10 dramatically shifts the active Rh atom from the apex position in free Rh 7 − to the edge position in "supported" Rh 7 − to enhance CH 4 adsorption, while the flexibility of C 20 H 10 to release electrons further promotes subsequent C−H activation. The Rh atoms in direct contact with the support serve as electron-relay stations for electron transfer between C 20 H 10 and the active Rh atom. This work not only establishes a novel approach to prepare and measure the reactivity of "supported" metal clusters in isolated gas phase but provides useful atomic-scale insights for understanding the chemical behavior of carbon (e.g., graphene)-supported metals in heterogeneous catalysis.

Regulating Excess Electrons in Reducible Metal Oxides for Enhanced Oxygen Evolution Reaction Activity: A Mini‐Review

“…In these electrochemical reactions, the octet rule is revealed as an essential factor governing the adsorption behaviors of reaction intermediates in response to varying NEE. Similarly, recent studies on photocatalysis by Zhao and Xu indicate the octet rule affecting both photoholes and photoelectrons in the CO oxidation and CO 2 activation on rutile TiO 2 (110) surface [52,53] . These similarities across electro‐ and photo‐catalytic reactions reinforce the universal applicability of the octet rule, suggesting a fundamental basis for tuning catalytic activities of various reactions on reducible metal oxide surfaces.…”

Four Undescribed Stilbenoid Derivatives from the Aerial Parts of Dendrobium officinale with their α‐Glucosidase and α‐Amylase Inhibitory Activity

“…Phytochemical study on the methanol extract of the aerial parts of D. officinale led to the isolation of four previously undescribed (1-4) and seven known compounds (5)(6)(7)(8)(9)(10)(11) (Figure 1). The known compounds were identified to be dendrocandin B (5), [16] dendromoniliside E (6), [17] dendrocandin A (7), [16] 4,4'dihydroxy-3,5-dimethoxybibenzyl (8), [18] 3,4-dihydroxy-5,4'-dimethoxybibenzyl (9), [16] moscatilin (10), [19] and 3',4-dihydroxy-3,5'-dimethoxybibenzyl (11), [20] by 1D-and 2D-NMR spectral data in comparison with those reported in the literature. Except 7 (identified by HPLC-ESI-MS), [21] compounds 5, 6, 8-11 have been isolated from some species of the genus Dendrobium including D. officinale.…”

Machine Learning for Experimental Reactivity of a Set of Metal Clusters toward C–H Activation

“…However, as Q min increases from −0.44 to 0.08 e (Figure C, right), the predicted reactivity increases (Figure C, right). Such an increase may be due to the favorable adsorption of small molecules on positive or less negative metal centers. − Note that in addition to the NPA charge, the AIM (Atoms in Molecules) , and Hirshfeld , charges for Q min values were also considered to train the BPANN model. It turned out that the performance of the BPANN model with the AIM charge is similar to that with the NPA charge, while the model with the Hirsfeld charge is worse than the other two (Figure S22).…”