A Hexagonal Covalent Porphyrin Framework as an Efficient Support for Gold Nanoparticles toward Catalytic Reduction of 4‐Nitrophenol

Abstract

A hexagonal porphyrin-based porous organic polymer, namely, CPF-1, was constructed by 3+2 ketoenamine condensation of the C -symmetric porphyrin diamine 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin and 1,3,5-triformylphloroglucinol. This material exhibits permanent porosity and excellent thermal and chemical stability. CPF-1 can be employed as a superior supporting substrate to immobilize Au nanoparticles (NPs) as a result of the strong interactions between Au NPs and the CPF support. An Au@CPF-1 hybrid was synthesized by an interfacial solution infiltration method with NaBH as reducing agent. Au NPs (5 nm) grew on CPF-1 and were distributed without aggregation. Moreover, Au@CPF-1 exhibits superior catalytic activity compared to many other reported Au-based catalysts for the reduction of 4-nitrophenol in the presence of NaBH . In addition, Au@CPF-1 has excellent stability and recyclability, and it can be reused for three successive reaction cycles without loss of activity. The dense distribution of phenyl rings on the channel walls of the CPF support can reasonably be regarded as the active sites that adsorb the 4-nitrophenol molecule through hydrogen-bonding and C-H⋅⋅⋅π interactions, as was confirmed by the X-ray structure of model compound DAPP-Benz.

Impedimetric Detection of Ammonia and Low Molecular Weight Amines in the Gas Phase with Covalent Organic Frameworks

“…1,3,5-Triformylphloroglucinol (TFP) was synthesized according to previous reports under a Duff reaction of phloroglucinol with hexamethylenetetramine (HMTA) [41]. All other reagents were purchased from commercial sources and used without previous purification.…”

Polydopamine as a bridge to decorate monodisperse gold nanoparticles on Fe3O4 nanoclusters for the catalytic reduction of 4-nitrophenol

“…Aer the addition of excess NaBH 4 solution, the characteristic absorption peak undergoes a redshi from 317 to 400 nm (curve b), whereas the characteristic absorption peak at 400 nm suggests the formation of a longer conjugative bonds with 4-nitrophenolate ions. 13 Aer the addition of the catalyst, the peak at 400 nm for 4nitrophenolate ions decreases rapidly, and only a peak at 300 nm in the ultra-violet region can be found (curve c). Correspondingly, as shown in Fig.…”

“…In addition, the K value for Fe 3 O 4 @PDA@Au obtained from 130 mM HAuCl 4 is 39.2 s À1 g À1 , which is also greatly higher than those obtained from other concentrations. We have also compared it with the values reported in literature using other different supports, and the abovementioned K value is found to be higher than those of the solid supports such as core-shell SiO 2 @Au composite particles (1.38 s À1 g À1 ), 35 carbon nanotubes functionalized with cyclotriphosphazene-containing polyphosphazene-loaded Au (5.93 s À1 g À1 ), 36 Au nanoparticles supported on iron oxides (5.25 s À1 g À1 ), 37 polymer-supported Au nanoparticles such as the hexagonal porphyrin-based porous organic polymer (0.25 s À1 g À1 ), 13 and alloy nanoparticles such as silver-gold alloy nanoparticles (34.7 s À1 g À1 ) synthesized using one-step gamma radiation. 38 The possible reason for this high K value is mainly the well-dispersion of Au NPs on Fe 3 O 4 @PDA and the effective protection of Au NPs from aggregation by PDA.…”

“…However, due to their high active surface atoms and strong van der Waals attraction, Au NPs exhibit a strong tendency to aggregate into larger clusters; this results in a change in their size and shape with deactivation or loss of their catalytic activity. 13 To offset this disadvantage, signicant efforts, including the use of capping reagents and other supports such as carbon nanotubes, 14 silica, and other metal oxides, 15,16 have been made to improve the stability of Au NPs. Since the catalytic performance of metal NPs is usually associated with their sizes and crystalline and electronic structures, the support should not block the surface of metal NPs and should maintain the small size and high stability of metal NPs.…”

Hierarchical AuNPs-Loaded Fe3O4/Polymers Nanocomposites Constructed by Electrospinning with Enhanced and Magnetically Recyclable Catalytic Capacities

“…Moreover, in addition to the excellent performances in CO low-temperature oxidation [ 9 , 10 , 11 ], the epoxidation of propylene [ 12 , 13 , 14 ], and water gas shift reactions [ 15 , 16 , 17 ], Au nanoparticles (AuNPs) show outstanding catalytic ability in liquid phase selective oxidation [ 18 , 19 , 20 ] and selective reduction [ 21 , 22 , 23 ]. However, the development of applications in liquid phase selective reduction of AuNPs catalysts have been critically restricted because the massive agglomeration of AuNPs results from their high surface energy and strong van der Waals attraction [ 24 ], so the catalytic activity shows a foreseeable sharp decrease in the liquid selective catalytic reduction system. In addition, the significant disadvantages of nanoscale AuNPs are their time-consuming separation [ 25 ], which provides an obstruction to facile catalyst recovery and recycling.…”