Facile Synthesis Hyper-Crosslinked PdFe Bimetallic Polymer as Highly Active Catalyst for Ullmann Coupling Reaction of Chlorobenzene

The synthesis of efficient and sustainable heterogeneous Pd-based catalysts has been an active field of research due to their crucial role in carbon-carbon coupling reactions. In this study, we developed a facile and eco-friendly in situ assembly technique to produce a PdFe bimetallic hyper-crosslinked polymer (HCP@Pd/Fe) to use as a highly active and durable catalyst in the Ullmann reaction. The HCP@Pd/Fe catalyst exhibits a hierarchical pore structure, high specific surface area, and uniform distribution of active sites, which promote catalytic activity and stability. Under mild conditions, the HCP@Pd/Fe catalyst is capable of efficiently catalyzing the Ullmann reaction of aryl chlorides in aqueous media. The exceptional catalytic performance of HCP@Pd/Fe is attributed to its robust absorption capability, high dispersion, and strong interaction between Fe and Pd, as confirmed by various material characterizations and control experiments. Furthermore, the coated structure of a hyper-crosslinked polymer enables easy recycling and reuse of the catalyst for at least 10 cycles without any significant loss of activity.

Rhodium nanoparticles confined in titania nanotubes for efficient Hydrogen evolution from Ammonia Borane

Designing efficient catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) have attracted considerable attention. Rhodium (Rh) based catalysts with rational design present remarkable catalytic performance for the reaction. Herein, we report the confined Rh@TiO₂ catalysts synthesized by atomic layer deposition combining with the sacrificial template approach, in which the Rh nanoparticles are uniformly confined on the inner surface of the porous titania nanotubes. The optimized catalysts show high catalytic activity with a turnover frequency value of 334.1 mol_H2·mol_Rh^-1·min^-1 and better durability. Mechanistic investigation demonstrates that the cleavage of OH bands in water should be the rate determining step, and the appropriate concentration of NaOH can further enhance the hydrogen evolution activity. The catalysts can also achieve the hydrogenation of various organic substrates using AB as the hydrogen source. In addition, our present strategy is general and can be extended to the synthesis of other confined catalysts for various catalytic reactions.

The Hydrogen-Storage Challenge: Nanoparticles for Metal-Catalyzed Ammonia Borane Dehydrogenation

Dihydrogen is one of the sustainable energy vectors envisioned for the future. However, the rapidly reversible and secure storage of large quantities of hydrogen is still a technological and scientific challenge. In this context, this review proposes a recent state-of-the-art on H₂ production capacities from the dehydrogenation reaction of ammonia borane (and selected related amine-boranes) as a safer solid source of H₂ by hydrolysis (or solvolysis), catalyzed by nanoparticle-based systems. The review groups the results according to the transition metals constituting the catalyst with a mention to their current cost and availability. This includes the noble metals Rh, Pd, Pt, Ru, Ag, as well as cheaper Co, Ni, Cu, and Fe. For each element, the monometallic and polymetallic structures are presented and the performances are described in terms of turnover frequency and recyclability. The structure-property links are highlighted whenever possible. It appears from all these works that the mastery of the preparation of catalysts remains a crucial point both in terms of process, and control and understanding of the electronic structures of the elaborated nanomaterials. A particular effort of the scientific community remains to be made in this multidisciplinary field with major societal stakes.

Controlled growth of ultrafine metal nanoparticles mediated by solid supports

As a unique class of nanomaterials with a high surface-area-to-volume ratio and narrow size distribution, ultrafine metal nanoparticles (UMNPs) have shown exciting properties in many applications, particularly in the field of catalysis. Growing UMNPs in situ on solid supports enables precise control of the UMNP size, and the supports can effectively prevent the aggregation of UMNPs and maintain their high catalytic activity. In this review, we summarize the recent research progress in controlled growth of UMNPs using various solid supports and their applications in catalysis.

Recent developments of nanocatalyzed liquid-phase hydrogen generation

Hydrogen is the most effective and sustainable carrier of clean energy, and liquid-phase hydrogen storage materials with high hydrogen content, reversibility and good dehydrogenation kinetics are promising in view of "hydrogen economy". Efficient, low-cost, safe and selective hydrogen generation from chemical storage materials remains challenging, however. In this Review article, an overview of the recent achievements is provided, addressing the topic of nanocatalysis of hydrogen production from liquid-phase hydrogen storage materials including metal-boron hydrides, borane-nitrogen compounds, and liquid organic hydrides. The state-of-the-art catalysts range from high-performance nanocatalysts based on noble and non-noble metal nanoparticles (NPs) to emerging single-atom catalysts. Key aspects that are discussed include insights into the dehydrogenation mechanisms, regenerations from the spent liquid chemical hydrides, and tandem reactions using the in situ generated hydrogen. Finally, challenges, perspectives, and research directions for this area are envisaged.

Facile Fabrication of Rhodium/Nanodiamond Hybrid as Advanced Catalyst toward Hydrogen Production from Ammonia–Borane

Hydrogen generation through ammonia–borane (AB) hydrolysis has been regarded as one of the most promising pathways to tap renewable green energy. The design and synthesis of highly effective catalysts toward hydrogen production from aqueous AB is of paramount significance. Here, the facile synthesis of Rh nanoparticles (NPs) immobilized on nanodiamond (nano-DA) and concomitant AB hydrolysis to produce hydrogen was successfully achieved. The in situ generated Rh/nano-DA exhibited excellent catalytic activity toward AB hydrolysis, with a high turnover frequency (TOF) value of 729.4 min−1 at 25 °C and a low activation energy of 25.6 kJ mol−1. Moreover, the catalyst could be reused four times. The unique properties of DA with abundant oxygen-containing groups enable the homogeneous distribution of small and surface-clean Rh NPs on the nano-DA surface, which can supply abundant accessible active sites for hydrogen evolution from AB hydrolysis. This study demonstrated that nano-DA can be applied as an ideal matrix to deposit efficient Rh nanocatalyst toward hydrogen evolution reaction.

Recent Advances in Noble Metal Catalysts for Hydrogen Production from Ammonia Borane

Interest in chemical hydrogen storage has increased, because the supply of fossil fuels are limited and the harmful effects of burning fossil fuels on the environment have become a focus of public concern. Hydrogen, as one of the energy carriers, is useful for the sustainable development. However, it is widely known that controlled storage and release of hydrogen are the biggest barriers in large-scale application of hydrogen energy. Ammonia borane (NH3BH3, AB) is deemed as one of the most promising hydrogen storage candidates on account of its high hydrogen to mass ratio and environmental benignity. Development of efficient catalysts to further improve the properties of chemical kinetics in the dehydrogenation of AB under appropriate conditions is of importance for the practical application of this system. In previous studies, a variety of noble metal catalysts and their supported metal catalysts (Pt, Pd, Au, Rh, etc.) have presented great properties in decomposing the chemical hydride to generate hydrogen, thus, promoting their application in dehydrogenation of AB is urgent. We analyzed the hydrolysis of AB from the mechanism of hydrogen release reaction to understand more deeply. Based on these characteristics, we aimed to summarize recent advances in the development of noble metal catalysts, which had excellent activity and stability for AB dehydrogenation, with prospect towards realization of efficient noble metal catalysts.

The design of hypercrosslinked polymers from benzyl ether self-condensing compounds and external crosslinkers

Hypercrosslinked polymers were produced via the self-condensation of benzyl ether compounds, providing a one-component route to highly porous networks and significant reductions in catalyst waste compared to conventional routes. These compounds also represent a new class of external crosslinkers, able to impart improved textural properties when compared to standard aliphatic crosslinkers.

A simple and straightforward strategy for synthesis of N,P co-doped porous carbon: an efficient support for Rh nanoparticles for dehydrogenation of ammonia borane and catalytic application

Metal nanoparticles (NPs) deposited on nitrogen (N)- and/or phosphorus (P)-doped porous carbon have been investigated as efficient catalysts for hydrolysis of ammonia borane (AB). However, the one-pot synthesis of N,P co-doped porous carbon using low-cost and readily available sources is still a tremendous challenge. Herein, a novel one-pot methodology is developed to fabricate N and P co-doped porous carbon (ATP-C) using non-precious and easily available adenosine triphosphate (ATP). The process of N and P doping does not need additional N or P sources in the material. Moreover, the entire process did not require chemical activation agents, making it more practical for large-scale applications. The resulting ATP-C supported Rh NPs (Rh/ATP-C) exhibit excellent performance for the catalytic hydrolysis of ammonia borane toward hydrogen generation, with a total turnover frequency (TOF) value of 566 mol H₂ min^-1 (mol Rh)^-1 and activation energy (E _a) of 26.3 kJ mol^-1. The catalytic system has shown an outstanding catalytic cycle life during the recycling tests. This work provides a novel method for the production of high performance carbon material supported metal NP catalysts for practical dehydrogenation applications.

Pyridine-based hypercrosslinked polymers as support materials for palladium photocatalysts and their application in Suzuki–Miyaura coupling reactions

Under ambient conditions, a Pd catalyst supported by a pyridine-based hypercrosslinked conjugated polymer shows excellent photocatalytic performance in S–M reactions.

A review of the antimicrobial potential of precious metal derived nanoparticle constructs

The field of nanotechnology is rapidly growing. The promise of pharmacotherapeutics emerging from this vast field has drawn the attention of many researchers. However, with the increase in the prevalence of antibiotic resistant microorganisms, the manifestations of these promises are needed now more than ever. Many have postulated the antimicrobial potential of nanoparticle constructs derived from precious metals/noble metals nanoparticles (NMNPs), such as silver nanoparticles that show activity against multidrug resistant bacteria. In this review we will evaluate the current studies and explore the data to obtain a clear picture of the potential of these particles and the validity of the claims of drug resistant treatments with NMNPs.

Hyper-Cross-Linked Polymer on the Hollow Conjugated Microporous Polymer Platform: A Heterogeneous Catalytic System for Poly(caprolactone) Synthesis

This work shows that the shape-controlled microporous organic polymer (MOP) can be utilized for the morphological engineering of another class of MOP materials. The morphology of a hyper-cross-linked polymer (HCP) was successfully engineered on the hollow conjugated microporous polymer (CMP). Through the postsynthetic modification of HCP bearing BINOLs (HCP-B) on the hollow CMP-like material (H-CMPL), the HCP bearing BINOL phosphoric acid (HCP-BP) was engineered on the H-CMPL platform. The resultant H-CMPL@HCP-BP showed good catalytic performance as a heterogeneous catalytic system and excellent recyclability in the ring-opening polymerization of ε-caprolactones to poly(caprolactone).

Ultrahigh Catalytic Activity of l-Proline-Functionalized Rh Nanoparticles for Methanolysis of Ammonia Borane

The synthesis of ultrafine and well-distributed rhodium nanoparticles (NPs) with high efficiency toward methanolysis of ammonia borane (AB) is crucially important but challenging. A facile approach has been developed for synthesizing ultrafine and uniform Rh NPs deposited on carbon by using the small soluble organic molecule (SOM) of l-proline (PRO) as capping agent (Rh-PRO/C). The enrichment of N,O-coordination sites for the metal precursor by using PRO was found to be the key to the synthesis Rh-PRO/C. The as-prepared Rh-PRO/C showed high catalytic activity for ammonia borane methanolysis with the highest total turnover frequency (TOF) of 1035 mol H 2  (mol_Rh  min)^-1 under basic conditions, which was three times higher than that of the state-of-the-art Rh-based catalysts. The excellent catalytic performance of Rh-PRO/C was ascribed to the well-dispersed Rh NPs and the PRO-functionalized metal surface, which can provide more active sites for the reaction. The merit of size-controlled synthesis combined with metal NP surface modification by SOMs is likely to be beneficial in various catalytic fields.

Towards High-Efficiency Hydrogen Production through in situ Formation of Well-Dispersed Rhodium Nanoclusters

Rh-based materials have emerged as potential candidates for hydrogen revolution from electrolyzing water or ammonia borane (AB) hydrolysis. Nevertheless, most of the catalysts still suffer from the complex synthetic procedures combined with limited catalytic activity. Additionally, the facile syntheses of Rh catalysts with high efficiencies for both electrochemical water splitting and AB hydrolysis are still challenging. Herein, we develop a simple, green, and mass-producible ion-adsorption strategy to produce a Rh/C pre-catalyst (pre-Rh/C). The ultrafine and clean Rh nanoclusters immobilized on carbon are achieved via the in situ reduction of the pre-Rh/C during the hydrogen-evolution process. The resulting in situ Rh/C catalyst presents an outstanding electrocatalytic performance with low overpotentials of 8 and 30 mV at 10 mA cm^-2 in 1.0 m KOH and 0.5 m H₂ SO₄ , respectively, outperforming the state-of-the-art Pt catalysts. Furthermore, the in situ Rh/C is also highly active for AB hydrolysis to produce hydrogen with a high turnover frequency of 1246 mol H2  mol_Rh^-1  min^-1 at 25 °C. The in situ-formed ultrafine Rh nanoclusters are responsible for the observed superior catalytic performance. This facile in situ strategy to realize a highly active catalyst shows promise for practical applications.