Au–Cu_xO_y Nanoparticles Encapsulated in Hollow Porous Silica Nanospheres as Efficient Catalysts for Nitrophenol Reduction

Abstract

In this work, Au−Cu x O y hybrid nanoparticle-encapsulated hollow porous silica nanospheres (Au−Cu x O y in HPSNs) were synthesized by immobilizing the catalytic functionality inside hollow cavities by using polyethyleneimine in a reverse microemulsion system as the void template as well as the platform to deliver the metals into the central voids. Compared with individual Au in HPSNs and Cu x O y in HPSNs, the prepared Au−Cu x O y in HPSNs demonstrate significantly improved catalytic efficiency for the reduction of various nitrophenols with NaBH 4 . At the molar ratio of 4-nitrophenol/Au of 30/1, the 4nitrophenol conversions over Au−Cu x O y in HPSNs reach 100% within 5.5 min, and catalytic efficiency is maintained during five cycles of catalytic reactions. The enhanced performance can be ascribed to the synergistic effect between Au and Cu x O y , and the protection of silica shells to inner Au−Cu x O y improve their catalytic stability.

Cascade Performance of Nitroarenes with Alcohols Boosted by a Hollow Flying Saucer-Shaped Ni–Al2O3 Catalyst via a MOF-Templated Strategy Induced by the Kirkendall Effect

“…From the FTIR spectrum of the Al-MOFs (Figure S1), the characteristic bands associated with the C�O (at 1720 cm −1 ) and C−O (at 1349 and 1273 cm −1 ) stretching vibrations of uncoordinated BTC ligand are absent. 34 As shown in Figure 1b,c, the 13 C MAS NMR spectra of Al-MOFs and the crystalline structure of a ligand unit, for the two regions, with chemical shifts of 170−175 ppm for carboxylate carbons (Figure 1c, C 2 site) and 130−140 ppm for aromatic carbons (Figure 1c, C 1 site), are clearly distinguishable. 35 Moreover, the 27 Al MAS NMR experiment for the as-prepared Al-MOFs was also employed.…”

“…Hollow structure catalysts exhibit extremely strong catalytic advantages in catalytic reactions due to their unique properties (e.g., confinement effect and fast mass transfer). − The utilization of hollow-structured catalysts in heterogeneous catalytic reactions necessitates their heightened demand for cascade reactions. − Because, the cascade catalytic synthesis allows for the execution of multiple steps in a single reaction using a one-pot synthetic procedure. As for hydrogenation–alkylation cascade reaction, the N -methylation reaction takes advantage of the in situ generation of arylamines through the hydrogenation of corresponding nitroarenes. − Numerous heterogeneous catalysts have been specifically designed and optimized with a focus on their stability, ease of separation, and recyclability. − Recently, metal–organic framework (MOF) materials have attracted widespread interest among researchers in the field of catalysis, particularly in the area of organic catalysis reactions. − These crystalline porous materials possess the advantages of both homogeneous and heterogeneous catalysis, making them highly versatile and efficient catalysts. Importantly, the use of MOF materials as catalyst supports shows great potential, especially in the synthesis of highly dispersed nanostructured metal catalysts …”

Confinement Effect of Hollow Nanoreactors Enforcing the Formation of Pd–NixOy Hybrid Nanoparticles Inside for 4-Nitrophenol Catalytic Reduction

“…A slower rate of reduction was observed with 0.0050 mmol of 4-NP used, which could be ascribed to the lower probability of collision between 4-NP and the catalyst particles. 55,56 Increasing the 4-NP amount to 0.050 mmol, the reaction rate increased rapidly, and the complete conversion was achieved within 6 min. Continuously increasing 4-NP amounts to 0.10 mmol only slightly decreases the reaction rate, demonstrating the good catalytic efficiency of Pd 1 -(Ni x O y ) 1/x @HPSNs.…”

Sodium Alginate–CdS Nanostructures: Reinforcing Chemoselectivity in Nitro-Organic Reduction and Dye Degradation through Photoinduced Electron Transfer

“…Thus, a chemoselective protection-free method is advantageous. Frequently, the selective reduction of nitro compounds is often carried out using NaBH 4 as a reducing agent to overcome the interim termination of the photocatalytic reaction. , However, the repulsion between the negative ions in aromatic nitro compounds and BH 4 – makes the photoredox reaction kinetically unfavorable, although it is thermodynamically possible at room temperature . Thus, a suitable photocatalyst can assist in overcoming the energy barrier during the photoreduction of compounds like NA, NP, and nitrostyrene (NS) to their respective amines.…”