Ultrafine AuPd Nanoclusters on Layered Double Hydroxides by the Capt-Capped AuPd Cluster Precursor Method: Synergistic Effect for Highly Efficient Aerobic Oxidation of Alcohols

A series of Ni₃Al–LDH-supported AuPd nanocluster (NC) catalysts Au_xPd_y/LDH (x/y = Au/Pd ratio upon the molar percentages of Au and Pd to the total metal; LDH: layered double hydroxide) were prepared by modified electrostatic adsorption of captopril-protected Au_xPd_y NCs onto the predispersed LDH support followed by proper calcination. The systematic characterizations reveal that the ultrafine Au_xPd_y NCs ranging from 1.4 ± 0.5 to 1.6 ± 0.5 nm with the Au/Pd ratios reducing from 96/4 to 61/39 are mainly dispersed on the edge of small LDH nanosheets in obtained catalysts Au_xPd_y/LDH. All of the catalysts Au_xPd_y/LDH exhibit higher aerobic oxidation activity of 1-phenylethanol than the monometallic Au₂₅/LDH, of which the Au₈₇Pd₁₃/LDH (1.5 ± 0.5 nm) shows the highest activity with turnover frequency (TOF) of 6810 h^–1 in toluene and an extremely high performance with TOF of 131 400 h^–1 under solvent-free condition, attributed to the ultrasmall Au₈₇Pd₁₃ NCs, the most electron-rich Au species formed by the electron transfer from Pd to Au and Ni-OH to Au₈₇Pd₁₃ NCs and the strongest Au₈₇Pd₁₃ NCs–LDH synergistic effect. Moreover, the catalyst maintains 98% of the initial conversion of 1-phenylethanol after 10 runs and possesses good adaptability for substrate alcohols.