High Activity and Stability of PdO_x Anchored in Porous NiO Nanofibers for Catalyzing Suzuki Coupling Reactions

Abstract

Heterogeneous Pd-based catalysts are receiving great attention in cross-coupling reactions due to their distinct advantages of relatively low cost, high stability, easy separation, and recycling. Nonetheless, great challenges still remain in developing heterogeneous catalysts with excellent performance and revealing the origin for efficient catalysis. Herein, we have synthesized a PdO x /NiO NFs catalyst consisting of porous NiO nanofibers and in situ anchored PdO x species by a facile electrospinning−pyrolysis strategy. The electron transfer from NiO to PdO created during the calcination step results in the formation of Pd δ+ (δ < 2) in the PdO x /NiO NFs, validated by both spectroscopic analyses and computational modeling. The PdO x /NiO NFs catalyst exhibits much higher activity than the commercial 5.0 wt % Pd/C and other as-prepared Pd-based catalysts in Suzuki coupling reactions. The turnover frequency (TOF) values for the conversions of iodo-, bromo-, and chlorobenzenes over the PdO x /NiO NFs catalyst are 6.6−7.3 times those over the commercial 5 wt % Pd/C catalyst. Theoretical calculations demonstrate that the configuration of PdO(101)/NiO(111) surface is more propitious to the adsorption and activation of arylhalide and phenylboronic acid than that of Pd(111)/NiO(111) surface. The compelling performance of PdO x /NiO NFs is mainly attributed to the special surface configuration of PdO x and unique electronic state of Pd δ+ species. These traits can be well retained in a long-term reaction owing to the strong metal−support interaction, ensuring the good durability of the catalyst. This study not only develops a promising heterogeneous catalyst with high performance for green synthesis of fine chemicals but also provides insights into the enhancement of catalytic activity achieved by modulating the active centers.

Rod‐Like MnOx Catalyst Derived from Mn‐MOF‐74 for Chlorobenzene Oxidation at Low Temperature

“…In addition, TOF is one of the most commonly used quantities describe the catalytic activity, which can provide a clear means to compare the activities of catalysts. [52] The TOF values for the conversions of CB over the MnO x catalysts were calculated at 180 °C, as shown in Table 1. The MnO x -600 and MnO x -700 revealed TOF values at approximately 2.14 × 10 À 7 and 2.52 × 10 À 7 s À 1 , respectively.…”

“…The superior catalytic activity of MnO x ‐700 sample might be due to the high specific surface area, better reducibility and abundant surface reactive oxygen species. In addition, TOF is one of the most commonly used quantities describe the catalytic activity, which can provide a clear means to compare the activities of catalysts [52] . The TOF values for the conversions of CB over the MnO x catalysts were calculated at 180 °C, as shown in Table 1.…”

New Palladium – ZrO2 Nano‐Architectures from Thermal Transformation of UiO‐66‐NH2 for Carbonylative Suzuki and Hydrogenation Reactions

“…[35,36] The high catalytic activity of PdO supported on different materials was also reported. [37][38][39][40][41] For example, PdO on graphene oxide [37] and PdO x on NiO [29] were found to be better catalysts than Pd/C. Advantages of PdO catalysts dispersed on the CNFs surface, [38] carbon nanotubes, [39] CeO 2 [40] or Ce x O y [41] were underlined.…”

“…This is in agreement with conclusion formulated for the Pd/NiO catalyst that absorption of bromobenzene or phenylboronic acid was stronger on the PdO surface than on the Pd. [29] Oxidative addition resulted in formation of aryl groups bonded to PdO. In the next step, migratory insertion of CO from Pd(0) produced acyl groups bonded to the catalyst surface.…”