Two new isolated Zn-ε-Keggin clusters modified by conjugated organic ligands with decent electrocatalytic and third-order NLO properties.

Two new bifunctional isolated hybrid compounds, [ε-PMoV8MoVI4O37(OH)3Zn4][iql]4·6H2O (1) and [ε-PMoV8MoVI4O38(OH)2Zn4][bipy]3[(CH3COO)(bipy)2Zn]·2H2O (2) (where iql = isoquinoline and bipy = 2,2'-bipyridine), based on Zn-ε-Keggin were successfully synthesized by self-assembly under hydrothermal conditions. It is interesting to note that acetate in 2 acted as a linker connecting the ε-Keggin anion with the one Zn atom (Zn5) and enabled the ε-Keggin anion to coordinate with more bipy ligands, culminating with a larger isolated system, which is the first reported isolated cluster of Zn5PMo12. Meanwhile, compounds 1-2 show great electrochemical behaviors and excellent electrocatalytic activity for the degradation of NaNO2.

Freezing copper as a noble metal-like catalyst for preliminary hydrogenation.

The control of product distribution in a multistep catalytic selective hydrogenation reaction is challenging. For instance, the deep hydrogenation of dimethyl oxalate (DMO) is inclined to proceed over Cu/SiO catalysts because of inevitable coexistence of Cu and Cu, leading to hard acquisition of the preliminary hydrogenation product, methyl glycolate (MG). Here, the oriented DMO hydrogenation into MG is achieved over the sputtering (SP) Cu/SiO catalysts with a selectivity of more than 87% via freezing Cu in a zero-valence state.

Importance of the Initial Oxidation State of Copper for the Catalytic Hydrogenation of Dimethyl Oxalate to Ethylene Glycol.

Exposing a Cu-based catalyst to a suitable temperature is of great importance to optimize its hydrogenation performance, as copper is sensitive to temperature. Herein, we investigated the effect of the initial oxidation state of copper, tuned by the reduction temperature, on its catalytic performance in the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) through designing a series of catalysts with different reduction temperatures (200-350 °C). Among these catalysts, the Cu/SiO catalyst prepared by ammonia evaporation with a hydrogen reduction process at 250 °C showed the best performance in the hydrogenation of DMO with a conversion of 100 % and a selectivity to EG higher than 95 %.