Ultrafine Platinum Nanoparticles Derived from Supramolecular Crystal for Catalytic Hydrogenation of Nitroarenes

Abstract

The development of a general synthetic approach for stable ultrafine heterogeneous nanocatalysts has attracted extensive attentions worldwide. However, the complex synthetic process and structure unstability have been recognized as the bottleneck of their investigation and practical application. Herein, a convenient and high selective platinum nanocatalyst was developed based from crystalline supramolecular hybrid solid materials. The macrocyclic decamethylcucurbit[5]uril (Me 10 CB [5]) and [PtCl 6 ] 2anions were firstly self-assembled into cyrstalline supramolecular solid in the presence of different alkali metal ions (Li ＋ , Na ＋ , K ＋ ). Then, ultrafine platinum (Pt) nanoparticles (NPs) have been successfully synthesized through in-situ reduction of cyrstalline supramolecular assemblies under mild thermal treatment at H 2 atmosphere. Uniform Pt NPs (ca. 3.0 nm) are produced and deposited on Me 10 CB[5] substrate to form M-Pt@Me 10 CB[5] (M＝Li ＋ , Na ＋ , K ＋ ) composite materials. The obtained Pt NPs are characterized extensively by a range of physical measurements including X-ray powder diffractions (PXRD), thermogravimetric analyses (TGA), inductively coupled plasma emission spectrometer (ICP), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The morphology and size of Pt NPs can be easily tuned through changing the original supramolecular structures. The different interaction between [PtCl 6 ] 2and Me 10 CB[5] capsulates affects the morphology and size of Pt NPs greatly. Such differences in geometric structures of Pt NPs have a significant impact on their catalytic performance. Moreover, the unique confinement effect provided by the supramolecular assembly as well as the special steric effect offered by macrocyclic Me 10 CB [5] suppresses the growth of Pt NPs during the reduction process. In addition, the atomic level uniform dispersion of Pt ions in ordered crystalline structure of the supramolecular assembly assures the uniform distribution of the final Pt NPs on the intact Me 10 CB [5], which acts as both a stabilizer and support. The Pt NPs obtained from Na ＋ and K ＋ constructed supramolecular assemblies exhibit high activity and chemoselectivity in catalytic hydrogenation of substituted nitrobenzenes to corresponding anilines under mild conditions. Meanwhile, the final Pt NPs also show an excellent stability in recycle test without dramatic loss of activity. This work demonstrates a novel, high-performance catalyst for the chemoselective hydrogenation reaction, and opens up a new approach for the preparation of nanocatalysts, which can be used in many other important fields, such as electrochemistry, energy science and environmental protection.

Cluster–Nuclei Coassembled One-Dimensional Subnanometer Heteronanostructures

“…1D subnanometer nanomaterials refer to 1D nanomaterials with diameters or thicknesses close to the size of a single unit cell, similar to polymer chains and biomacromolecules, , including subnanometer nanowires (SNWs) and subnanometer nanobelts (SNBs). They show ultrahigh specific surface area , and have a strong interaction with the external fields, bringing excellent catalytic − and energy conversion performance , and so on. Moreover, the dimensional similarity brings polymer-analogue properties, such as conformation, rheology, and self-assembling behavior, , so the SNWs and SNBs can be processed like polymers, leading to wider application fields. − In the past few years, our group has developed a general experimental “good/poor solvent” system for the facile synthesis of SNWs and SNBs , and reported a series of 1D subnanometer nanomaterials, such as GdOOH SNWs, tungsten bronze SNWs, tungsten oxide SNBs, and palladium-based SNBs .…”

Chiral Conformation of Subnanometric Materials

“…Apart from these achievements, the most important gift from the boom of nanochemistry is the belief that the size of materials plays a decisive role in their properties. The progress of nanochemistry has inspired many researchers to explore the size-dependent properties of nanomaterials with smaller size, resulting in a bulk of reports about ultrathin or ultrafine nanomaterials. − As the definition of ultrafine nanomaterials is ambiguous, we suggest the term, SNMs, to refer to the nanomaterials with size near the diameter of linear polymers and the size of a single unit cell in at least one dimension. , Thanks to the recent development of synthetic methods to control the growth of materials at subnanometric scale, such as cluster-nuclei coassembly, an increasing amount of SNMs is reported. − Consequently, more and more facts support that the subnanometric size endows SNMs with conspicuously different properties compared to their counterparts with larger sizes …”