PdAu alloy nanoparticles supported on nitrogen-doped carbon black as highly active catalysts for Ullmann coupling and nitrophenol hydrogenation reactions

Abstract

The PdAu/NCB catalyst with a Pd/Au mole ratio of 1/1 shows the highest activity towards both Ullmann coupling reactions of aryl halides and the hydrogenation reaction of nitrophenols.

Recent Advances in Supported Bimetallic Pd–Au Catalysts: Development and Applications in Organic Synthesis with Focused Catalytic Action Study

“…The catalyst was found to be efficient in terms of reactivity toward less-reactive aryl chlorides and recyclability with appreciable TOF values (Scheme a) . Later on, under ambient temperature (40 °C), Ullmann coupling efficiency also has been improved along with excellent conversion and selectivity, which have followed from ensemble effects as well as increased electron density on Pd atoms in Pd–Au NPs. , The effect of support selection, catalyst preparation method, and metal ratio can be clearly seen in the below given examples (Scheme b, c).…”

“…The selection of catalyst preparation method and its modification is a deciding factor for final catalyst performance as the preparation of supported BMCs is more tedious than monometallic because of parameters such as the exact desired metal composition and bimetallic formation. Therefore, different methods for supported Pd–Au BMCs preparation have been developed such as deposition precipitation, − wet impregnation, − reduction deposition, − coreduction, , photochemical reduction, sol-immobilization, − coprecipitation, ion-exchange, metal sputtering, , sol–gel, sono-photodeposition, electroless deposition, and so on. The efficacy comparison of various adopted methods for preparation of Pd–Au BMCs is quite difficult as their selection is directly related to the nature of anchoring support.…”

“…146 Later on, under ambient temperature (40 °C), Ullmann coupling efficiency also has been improved along with excellent conversion and selectivity, which have followed from ensemble effects as well as increased electron density on Pd atoms in Pd−Au NPs. 33,132 The effect of support selection, catalyst preparation method, and metal ratio can be clearly seen in the below given examples (Scheme 9b, 132 c 33 ). the Pd/C has been stabilized with Au to avoid the leaching and increase the recyclability (Scheme 10).…”

“…In addition, the pore size and the chemical properties (polarity and hydrophobicity) also can be altered as per the requirement of an application, and a metal’s recovery can be done by simply burning the carbon support. The carbon-supported Pd NPs were alloyed with Au metal, which led to improved stabilization and recyclability for the Sonogashira reaction, and Ullmann coupling of aryl halides and activated carbon supported Pd–Au BMCs also has been performed for hydrogenation of nitrophenol in an efficient manner. , The stability of Au/C catalyst was improved with Pd metal addition which led to enhanced catalyst recyclability during 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furandicarboxylic acid (FDCA) . From an environmental application perspective, granular activated carbon and graphene supported Pd–Au BMCs were efficiently applied for HDC of trichloroethylene (TCE), which is a well-known volatile organic compound (VOC) .…”

Supported Pd–Au bimetallic nanoparticles as an efficient catalyst for the hydrodeoxygenation of vanillin with formic acid at room temperature

“…44 Besides, the electron deficit could also be compensated by the support, which may be due to the large π–π conjugation of the cyanuric structure in g-C 3 N 4 . 45,46 The electron transfer from support to metals is evidenced by the N 1s spectra (Fig. 3e).…”