Ultrathin Amorphous/Crystalline Heterophase Rh and Rh Alloy Nanosheets as Tandem Catalysts for Direct Indole Synthesis

Abstract

Heterogeneous noble‐metal‐based catalysis plays an essential role in the production of fine chemicals. Rh‐based catalysts are one of the most active candidates for indole synthesis. However, it is still highly desired to develop heterogeneous Rh‐based catalysts with high activity and selectivity. In this work, a general, facile wet‐chemical method is reported to synthesize ultrathin amorphous/crystalline heterophase Rh and Rh‐based bimetallic alloy nanosheets (NSs), including RhCu, RhZn, and RhRu. Impressively, the amorphous/crystalline heterophase Rh NSs exhibit enhanced catalytic activity toward the direct synthesis of indole compared to the crystalline counterpart. Importantly, the obtained amorphous/crystalline heterophase RhCu alloy NSs can further enhance the selectivity to indole of >99.9% and the conversion is 100%. This work demonstrates the importance of phase engineering and metal alloying in the rational design and synthesis of tandem heterogeneous catalysts toward fine chemical synthesis.

Synthesis and electrocatalytic performance of ultrathin noble metal nanosheets

“…The addition of DETA is very important for the formation of ultrathin alloy nanosheets. DETA chelates with Pt 4+ and Pd 2+ 78 to form coordination compounds, change the oxidationreduction potential of the metal precursor, and reduce the metal reduction rate. The resulting slow kinetics allow crystals to grow anisotropically.…”

“…, Zhu et al and Ge et al both obtained three-dimensional structures containing two-dimensional ultrathin nanosheets as structural units. The thicknesses of their nanosheets are only 1.7 and 1.3 nm, respectively 77,78. …”

“…Fig. 11 (a) TEM and (b) AFM images of the single-layer Rh nanosheet; 52 (c) TEM, (d) HRTEM, and (e) AFM images of the Rh nanosheet; 76 (f) SEM, (g) TEM, and (h) AFM images of hierarchical porous Rh nanosheets; 77 (i) SEM, (j) DF-STEM, and (k) TEM images of amorphous/crystalline heterophase Rh nanosheets 78. …”

Controlling Multiple Active Sites on Pd−CeO2 for Sequential C−C Cross‐coupling and Alcohol Oxidation in One Reaction System

“…The products of this type of multistep one-pot process can be utilized as useful building blocks for biologically active compounds. [49] As a representative example showing this potential, biphenyl-4-carboxaldehyde (8 a) was further transformed into commercial pharmaceuticals such as the antifungal drug bifonazole (10) and the anti-inflammatory drug felbinac (11), as shown in Figure 5b.…”

“…For example, zeolite was chosen to create acid sites for sequential condensation and hydrogenation, [8] and noble metals and their alloys were utilized to promote several multistep organic reactions in one reaction system. [9,10] Ceria (CeO 2 ), a representative reducible oxide, is a promising candidate for a multifunctional catalyst because CeO 2 not only has a unique Ce 3 + /Ce 4 + redox property [11,12] but also acts as a stable support for metal catalysts through strong interactions between metal and CeO 2 . [13][14][15][16] The redox-related catalytic properties of CeO 2 are closely related to its local surface structure, such as exposed facets and crystallite size.…”