Partially Thiolated Au<sub><i>n</i></sub> (<i>n</i> = 25, 102) Clusters on Layered Double Hydroxides Anchored by Electrostatic Interactions: Size Effect on 5-Hydroxymethylfurfural Oxidation Catalysis
Shinya Masuda, Tatsuya Tsukuda
Abstract
Robust heterogeneous Au cluster catalysts were synthesized with atomic precision by the controlled thermal aging of p -mercaptobenzoic acid ( p MBA)-protected Au n clusters ( n = 25 or 102) on a layered double hydroxide (LDH). Au 25 ( p MBA) 18 or Au 102 ( p MBA) 44 was adsorbed on the LDH during the coprecipitation process and heated at 225 °C for 24 h. X-ray absorption fine structure analysis showed that part of the p MBA remained upon appropriate thermal aging owing to the electrostatic interaction between the deprotonated p MBA and cationic LDH. The electrostatic interaction stabilized the Au n clusters not only during the aging but also during the catalytic usage. The Au 102 catalyst exhibited 22 times higher activity than that of the Au 25 catalyst for 5-hydroxymethylfurfural oxidation. Such remarkable catalytic promotion by the Au 102 catalyst is ascribed to the size-specific electronic structure, which facilitates abstraction of hydride from the adsorbed alkoxide.