Platinum group nanoparticles doped BCN matrix: Efficient catalysts for the electrocatalytic reduction of nitrate to ammonia

The effective treatment of nitrate (NO3-) in water as a nitrogen source and electrocatalytic NO3- reduction to ammonia (NH3) (NRA) have become preferred methods for NO3--to-NH3 conversion. Achieving efficient NO3--to-NH3 conversion requires the design and development of electrode materials with high activity and efficiency for the electrocatalytic NRA reaction. Herein, based on the special properties of dodecahydro-closo-dodecaborate anions, a BCN matrix, loaded with platinum-group nanoparticles (namely, Pd/BCN, Pt/BCN, and Ru/BCN), was prepared using a simple method for the electrocatalytic NRA reaction. Results showed that Pd/BCN exerts the best catalytic effect on the NRA reaction. The NH3 production rate reached 12.71 mg h-1 mgcat.-1 at -1.0 V vs. RHE. Faraday efficiency reached 91.79 %, which can be attributed to the more uniform distribution of the nanoparticles. Furthermore, Pd/BCN exhibited high cycling stability and resistance to ionic interference. Moreover, the density functional theory calculations indicated that small and well-distributed Pd nanoclusters in the BCN matrix have a large active surface area and promote the catalytic process. This study provides a new strategy to design catalysts for green ammonia synthesis.

Functionalization of Dodecaborates by Mild and Efficient Pd-Catalyzed Formation of B-C Bonds with Boronic Acids

Hybrid organic-inorganic molecules have recently received great interest due to their unique properties, which give access to their implementation in biological and material sciences. Herein, a new synthetic approach for the direct-linkage of the purely inorganic dodecaborate cluster to organic building blocks through B-C bond is established, using boronic acids as functional groups on the organic moiety, reacting under Suzuki-Miyaura coupling conditions with iodo-undecahydridododecaborate. The choices of ligand (DavePhos) and solvent (N-methylpyrrolidone for electron-poor, CD3 CN for electron-rich groups) are essential for the successful coupling. Ultimately, the newly described methodology is found to be functional-group tolerant covering a wide spectrum of substrates including electron-poor arenes.

Synthesis of Derivatives of closo-Dodecaborate Anion Based on Amino Acid Esters

Abstract

This work proposes a new method for the synthesis of N-borylated amino acids based on nucleophilic substitution reactions in the [B12H11IPh]– anion. Esters of glycine and L-phenylalanine were used as nucleophiles. The structure of the products has been determined by multinuclear NMR spectroscopy, IR spectroscopy, and ESI mass spectrometry.

Efficient Ambient Electrocatalytic Ammonia Synthesis by Nanogold Triggered via Boron Clusters Combined with Carbon Nanotubes

Currently, the development of stable electrochemical nitrogen reduction reaction (ENRR) catalysts with high N₂ conversion activity and low cost to instead of the traditional Haber-Bosch ammonia production process of high-energy consumption remains a great challenge for researchers. Here, we have immobilized reductive closo-[B₁₂H₁₁]^- boron clusters on a carbon nanotubes (CNT) surface and have successfully prepared a novel Au-CNT catalyst with extraordinary ENRR activity after adding HAuCl₄ to the CNT-[B₁₂H₁₁]^- precursor. The excellent properties of ammonia yield (57.7 μg h^-1 cm^-2) and Faradaic efficiency (11.97%) make it possible to achieve using this Au-CNT catalyst in large-scale industrial production of ammonia. Furthermore, its outstanding cyclic stability and long-term tolerability performance make it one of the most cost-effective catalysts to date. Here, by means of density functional theory we disclose the associative mechanism of N₂-to-NH₃ conversion on the Au(111) surface, providing visual theoretical support for the experimental results.

Directed B–H functionalization of the closo-dodecaborate cluster via concerted iodination–deprotonation: reaction mechanism and origins of regioselectivity

A concerted iodination–deprotonation process was discovered for the B–H bond iodination of closo-dodecaborate cluster, which is responsible for the regioselectivity of ortho-B–H functionalization.

New perspective of a nano-metal preparation pathway based on the hexahydro-closo-hexaborate anion

Today, metal-based nanomaterials play an increasingly important role in the energy, environment, medical and health fields. In order to meet the needs of various fields, it is necessary to continuously develop advanced technologies for preparing metal-based materials. Inspired by previous research, the results of a proof-of-concept experiment show that the hexahydro-closo-hexaborate anion (closo-[B₆H₇]⁻) in the borane cluster family has properties similar to NaBH₄. Closo-[B₆H₇]⁻ can not only convert common precious metal ions such as Au³⁺, Pd²⁺, Pt⁴⁺ and Ag⁺ to the corresponding zero-valence state, but also convert some non-precious metals such as Cu²⁺ and Ni²⁺ to the zero-valent or oxidation state. Closo-[B₆H₇]⁻ moderate reduction to cause rapid aggregation of metal-based materials is not easy compared with NaBH₄. Compared with closo-[B₁2H₁₂]²⁻, closo-[B₆H₇]⁻ achieves the conversion of Pt⁴⁺ to Pt⁰ under ambient conditions, and its reduction performance extends to non-precious metals. The excellent stability and easy modification characteristics determine the universality of the closo-[B₆H₇]⁻ reduction strategy for metal ions.

Today, metal-based nanomaterials play an increasingly important role in the energy, environment, medical and health fields.

Ionic Liquid-Responsive Phase Transfer of Gold Nanoparticles: Anionic Metathesis

In this work, a fresh approach has been proposed for the efficient transfer of gold nanoparticles (AuNPs) from an aqueous to organic phase by the metathesis reaction or anion exchange reaction. Here, we synthesized ionic liquid 1-butyl 3-hexadecyl imidazolium bromide [C₄C₁₆Im]Br-stabilized AuNPs which exhibit excellent stability in solution. Transfer of Au@[C₄C₁₆Im]Br from an aqueous to organic phase was investigated by the metathesis reaction with different hydrophobic ionic liquid-forming salts such as LiNTf₂, LiClO₄, and KPF₆. The anionic exchange process in ionic liquids at the AuNP surface to make hydrophilic to hydrophobic AuNPs is demonstrated. It was found that hydrophobic ionic liquids provide the most effective transfer of AuNPs from the aqueous to organic phase. Interestingly, we have noticed no change in color, size, and shape of AuNPs for more than a month, indicating more efficient transfer of AuNPs in organic solvents, which remained stable for over a month. The ionic liquids with anions NTf₂^-, ClO₄^-, and PF₆^- make the AuNP surface hydrophobic, indicating their good dispersibility in nonpolar solvents. Finally, these AuNPs exhibit excellent sensitivity toward the refractive index of organic solvents, which is correlated with the surface plasmon resonance (SPR) λ_SPR bands.

Shape-Controlled Dodecaborate Supramolecular Organic-Framework-Supported Ultrafine Trimetallic PtCoNi for Catalytic Hydrolysis of Ammonia Borane

On the basis of the unique chaotropic supramolecular assembly of cucurbit[5]uril (CB5) and dodecahydro- closo-dodecaborate anion [ closo-B₁₂H₁₂]^2-, we have developed an efficient and universal platform to fabricate shape-controlled dodecaborate-based supramolecular organic frameworks (BOFs) decorated with ultrafine monodispersed trimetallic alloys. Simply by regulating the molar ratio of CB5 and [ closo-B₁₂H₁₂]^2-, a series of fascinating morphologies, such as flowerlike structures, nanorods, nanocubes, and nanosheets, were successfully constructed. These obtained BOFs were proved to be good substrate supports for in situ synthesis of trimetallic PtCoNi nanoalloys, where the final PtCoNi-BOFs materials were obtained efficiently as a precipitate from aqueous solutions, and showed excellent catalytic performance in ammonia borane hydrolysis with a high turnover frequency of 1490 mol_H2 mol_Pt^-1 min^-1 and a low activation energy of 15.79 kJ mol^-1.

Polyhedral borane-capped coinage metal nanoparticles as high-performing catalysts for 4-nitrophenol reduction

Small (<5 nm) gold and silver nanoparticles and their bimetallic counterparts were prepared using the fundamental boron cluster [closo-B₁₀H₁₀]²⁻ as the reducing and stabilizing agent.

Boron based nanosheets as reducing templates in aqueous solutions: towards novel nanohybrids with gold nanoparticles and graphene

We show that nanosheets obtained by exfoliating magnesium diboride bear an intrinsic ability to elicit chemical reduction of quinone-based molecules. They also reduce gold salt into ultra-small gold nanoparticles and graphene oxide into reduced graphene oxide. These nanosheets subsequently interface with the partner nanomaterial in solution to form novel nanohybrids.

In situ synthesis of ultrafine metal clusters triggered by dodecaborate supramolecular organic frameworks

Supramolecular nano-assemblies with tunable morphology have attracted extensive attention in composite material manufacturing and many other fields. Herein, a new class of shape-controlled dodecaborate-based supramolecular organic frameworks (BOFs), decorated with diverse ultrafine noble metal clusters (Au, Pd, Pt, Ag), has been successfully fabricated via the tunable host-guest assembly of cucurbit[n = 5,6,7,8]uril and Cs2[closo-B12H12]. Due to the unique dodecaborate-cucurbit[n]uril chaotropic effect, a breakthrough has been made in modulating the supramolecular frameworks in the urchin-like, network-like or octahedron-like structures without tedious chemical modifications or additional additives. More interestingly, Cs2[closo-B12H12], a prominent component in supramolecular structures, can also play dual roles as an excellent reductant and capping agent for the formation of metal clusters. The final product, i.e., BOFs decorated with ultrafine metal clusters (metal/BOFs) can be precipitated from aqueous solutions rapidly and they show high catalytic activity and recyclability in Suzuki reactions and in the selective reduction of furfural (FAL) to furfuryl alcohol (FOL).

The Chaotropic Effect as an Assembly Motif in Chemistry

Following up on scattered reports on interactions of conventional chaotropic ions (for example, I- , SCN- , ClO4- ) with macrocyclic host molecules, biomolecules, and hydrophobic neutral surfaces in aqueous solution, the chaotropic effect has recently emerged as a generic driving force for supramolecular assembly, orthogonal to the hydrophobic effect. The chaotropic effect becomes most effective for very large ions that extend beyond the classical Hofmeister scale and that can be referred to as superchaotropic ions (for example, borate clusters and polyoxometalates). In this Minireview, we present a continuous scale of water-solute interactions that includes the solvation of kosmotropic, chaotropic, and hydrophobic solutes, as well as the creation of void space (cavitation). Recent examples for the association of chaotropic anions to hydrophobic synthetic and biological binding sites, lipid bilayers, and surfaces are discussed.