Search

The novel nanomaterials AuxPdy@ZIF-8 catalyze H2-producing ammonia borane methanolysis; the reaction is considerably boosted by visible-light irradiation and ZIF-8 surpassing other supports. KIE studies and DFT calculations delineate the mechanism.

Highly efficient three-dimensional Co and N co-doped carbon nanocuboids (CoN/CNCs) have been first designed and synthesized, via doping of Co and N atoms onto carbon nanocuboids, for an enhanced oxygen reduction reaction.

The construction of biomass-based conductive hydrogel e-skins with high mechanical properties is the research hotspot and difficulty in the field of biomass materials. Traditional collagen-based conductive hydrogels, constructed by the typical “bottom–up” strategy, normally have the incompatible problem between high mechanical property and high collagen content, and the extraction of collagen is often necessary. To solve these problems, inspired by the high mechanical properties and high collagen content of animal skins, this work proposed a “top–down” construction strategy, in which the extraction of collagen was unnecessary and the skin collagen skeleton (SCS) with the 3D network structure woven by natural collagen fibers in goatskin was preserved and used as the basic framework of hydrogel. Following a four-step route, namely, pretreatment → soaking in AgNPs (silver nanoparticles) solution → soaking in the mixed solution containing HEA (2-hydroxyethyl methacrylate) and AlCl3 → polymerization, this work successfully achieved the fabrication of a new skin-based conductive hydrogel e-skin with high mechanical properties (tensile strength of 2.97 MPa, toughness of 6.23 MJ·m−3 and breaking elongation of 428%) by using goatskin as raw material. The developed skin hydrogel (called PH@Ag) possessed a unique structure with the collagen fibers encapsulated by PHEA, and exhibited satisfactory adhesion, considerable antibacterial property, cytocompatibility, conductivity (3.06 S·m−1) and sensing sensitivity (the maximum gauge factor of 5.51). The PH@Ag e-skin could serve as strain sensors to accurately monitor and recognize all kinds of human motions such as swallowing, frowning, walking, and so on, and thus is anticipated to have considerable application prospect in many fields including flexible wearable electronic devices, health and motion monitoring. Graphical abstract

International audience; Although the chemistry of carbonyl-protected platinum nanoclusters is well established, their bonding mode remains poorly understood. In most of them, the average Pt oxidation state is zero or slightly negative, leading to the apparent average configuration 5d(10) 6s(epsilon) (epsilon = 0 or very small) and the apparent conclusion that metal-metal bonding cannot arise from the completely filled 5d shell nor from the empty (or almost empty) 6s orbitals. However, DFT calculations show in fact that in these species the actual average configuration is 5d(10-x) 6s(x), which provides to the whole cluster a significant total number of 6s electrons that ensures metal-metal bonding. This ("excited") average configuration is to be related to that of coinage metals in ligated group 11 nanoclusters (nd(10) (n + 1)s(x)). Calculations show that metal-metal bonding in most of these platinum nanoclusters can be rationalized within the concepts of superatoms and supermolecules, in a similar way as for group 11 nanoclusters. The "excited" 5d(10-x) 6s(x) configuration results from a level crossing between 5d combinations and 6s combinations, the former transferring their electrons to the latter. This level crossing, which does not exist in the bare Pt-n clusters, is induced by the ligand shell, the role of which being thus not innocent with respect to metal-metal bonding.

A simple and surfactant-free method was successfully employed to construct M16Pd1/C bimetallic nano-materials for direct H2 production by SF decomposition in the presence of acetic acid.

Highly efficient graphene-like carbon nanosheet stabilized Pd, Rh and Ru nanohybrids have been developed as robust catalysts for H2 generation from the hydrolysis of organosilane, C–C coupling and reduction of 4-nitrophenol for the first time.

A bulky organocobalt sandwich-supported Rh nanoparticle is an efficient, stable and recyclable nanocatalyst for hydrolysis of both ammonia borane and tetrahydroxydiboron to H2.

The rational design of highly efficient PtNi@ZIF-8 nanocatalyst and the understanding of the hydrogen generation process for selective and complete decomposition of hydrazine borane (HB) are disclosed.

International audience; Hydrogen (H2) generation and storage are actively investigated to provide a green source of energy, and formic acid (HCOOH), a major product obtained from the biomass, is regarded as a productive source of H2. Therefore, improvements in heterogeneous catalysts are called for. Here, a novel type of catalyst support is proposed involving simple addition of the mixture of metal ion precursors to core-shell ZIF-8@ZIF-67, followed by reduction with NaBH4, with performances surpassing those obtained using nanocatalysts in ZIF-8 or ZIF-67. The nanocatalysts PdxAg were optimized with ZIF-8@Pd2Ag1@ZIF-67 under visible-light illumination for selective HCOOH dehydrogenation involving a turnover frequency value of 430 h-1 under light irradiation at 353 K. These results also reveal the crucial roles of the Pd sites electronically promoted in the presence of visible by the plasmon resonance and the core-shell light by Ag plasmon advantageous MOF structure. In order to examine the potential of extending this catalyst improvement principle to other catalytic reactions, 4nitrophenol reduction, a benchmarking model of catalytic reaction, was tested, and the results also confirmed the superiority of the performance of ZIF-8@Pd2Ag1@ZIF-67 over Pd2Ag1@ZIF-8 and Pd2Ag1@ZIF-67, confirming the interest in the novel catalyst design.

Ferrocene is precursor of [FeCp(arene)]n+ (n = 0–2), redox and electrocatalysts and motifs generating dendrimer cores upon multiple C–C bond formations. Dendrimer functionalization including with ferrocene led to numerous properties and applications.

Electron transfer plays a major role in chemical reactions and processes, and this is particularly true of catalysis by nanomaterials. The advent of metal nanoparticle (NP) catalysts, recently including atomically precise nanoclusters (NCs) as parts of nanocatalyst devices has brought increased control of the relationship between NP and NC structures and their catalytic functions. Consequently, the molecular definition of these new nanocatalysts has allowed a better understanding and management of various kinds of electron transfer involved in the catalytic processes. This Minireview brings a chemist's view of several major aspects of electron-transfer functions concerning NPs and NCs in catalytic processes. Particular focus concerns the role of NPs and NCs as electron reservoirs and light-induced antenna in catalytic processes from H2 generation to more complex reactions and sustainable energy production.

The first all‐metallocene rechargeable battery consisting of poly‐cobaltocenium/‐ and poly‐ferrocene/reduced graphene oxide composites as anode and cathode was prepared. The intrinsically fast ET self‐exchange rate of metallocenes was successfully combined with an efficient ion‐percolation achieved by molecular self‐assembly. The resulting battery materials show ideal Nernstian behavior, is thickness scalable up to >1.2 C cm−2, and exhibit high coulombic efficiency at ultrafast rates (200 A g−1). Using aqueous LiClO4, the charge is carried exclusively by the anion. The ClO4 − intercalation is accompanied by a reciprocal height change of the active layers. Principally, volume changes in organic battery materials during charging/discharging are not desirable and represent a major safety issue. However, here, the individual height changes—due to ion breathing—are reciprocal and thus prohibiting any internal pressure build‐up in the closed‐cell, leading to excellent cycling stability., An all‐metallocene battery consisting of poly‐ferrocene and poly‐cobaltocene is shown. The extremely high power density is provided via molecular self‐assembly between polymers and reduced graphene oxide. The precise construction of anode and cathode results in a reciprocal height change during charging–discharging, due to anion (de)intercalation in the soft structure.

Biomass valorization is essential, particularly in emerging countries. Here, hydrochar from arabica coffee straw was functionalized with a triazole group (HD-TRz) for use as a support of palladium nanoparticles (PdNPs-HD-TRz) applied in the Ullmann coupling reaction for the first time. It provided remarkably excellent selectivities, conversions at a temperature as low as 45 °C and catalyst recyclability, surpassing previous literature performances. Hydrochar was obtained by one-pot reaction via hydrothermal synthesis, using NaOH solution as activating agent and functionalized with a 1,3-triazole group by CuAAC "click" reaction. The PdNPs were prepared via reduction of hydrochar-bound Pd(II) using NaBH

The classic Fokin mechanism of the CuAAC reaction of terminal alkynes using a variety of Cu(I) catalysts is well-known to include alkyne deprotonation involving a bimetallic σ,π-alkynyl intermediate. In this study, we have designed a CNT-supported atomically precise nanocluster Au4Cu4 (noted Au4Cu4/CNT) that heterogeneously catalyzes the CuAAC reaction of terminal alkynes without alkyne deprotonation to a σ,π-alkynyl intermediate. Therefore, three nanocluster-π-alkyne intermediates [Au4Cu4(π-CH≡C-p-C6H4R)], R = H, Cl, and CH3, have been captured and characterized by MALDI-MS. This Au4Cu4/CNT system efficiently catalyzed the CuAAC reaction of terminal alkynes, and internal alkynes also undergo this reaction. DFT results further confirmed that HC≡CPh was activated by π-complexation with Au4Cu4, unlike the classic dehydrogenation mechanism involving the bimetallic σ,π-alkynyl intermediate. On the other hand, a Cu11/CNT catalyst was shown to catalyze the reaction of terminal alkynes following the classic deprotonation mechanism, and both Au11/CNT and Cu11/CNT catalysts were inactive for the AAC reaction of internal alkynes under the same conditions, which shows the specificity of Au4Cu4 involving synergy between Cu and Au in this precise nanocluster. This will offer important guidance for subsequent catalyst design.

Highly catalytically active core–shell nanoparticles (NPs) have attracted great attention towards applications. Herein, core–shell Au@AgNPs were simply obtained via a green and cheap one-step method using tannic acid (TA) as both a reductant and a stabilizer. TA was used to cross-link poly(vinyl alcohol) (PVA), forming a PVA/TA hydrogel with the repeated freezing–thawing method. The gelation mechanism was confirmed by urea-treatment experiment, UV-vis, IR, TG, and DSC. The freezing–thawing treatment endows TA and PVA with better conditions to form hydrogen bonds, and the intensive hydrogen bond interactions and weak crystallization interactions work in synergy to maintain the three-dimensional network of the PVA/TA hydrogel. Owing to favorable mechanical properties and suitable pore size, the PVA/TA hydrogel further served as a support for the immobilization of Au@AgNPs that exhibited excellent and recyclable catalytic degradation ability for 4-nitrophenol, 2-nitrophenol, methylene blue, and Congo red.

By introducing 1,1′-bis-(diphenylphosphino)ferrocene (dppf) as an activating ligand, two novel nanoclusters, M1Ag21 (M = Au/Ag), have been controllably synthesized and structurally characterized. The atomically precise structures of the M1Ag21 nanoclusters were determined by SCXC and further confirmed by ESI-TOF-MS, TGA, XPS, DPV, and FT-IR measurements. The M1Ag21 nanoclusters supported on activated carbon (C) are exploited as efficient oxygen reduction reaction (ORR) catalysts in alkaline solutions. Density functional theory (DFT) calculations verify that the catalytic activities of the two cluster-based systems originate from the significant ensemble synergy effect between the M13 kernel and dppf ligand in M1Ag21. This work sheds lights on the preparation of cluster-based electrocatalysts and other catalysts that are activated and modified by peripheral ligands., The presence of 1,1′-bis-(diphenylphosphino)ferrocene ligands and ensemble effects in novel nanoclusters M1Ag21(dppf)3(SAdm)12 (M = Au/Ag) provide excellent ORR performances.

A new dual-decontamination strategy has been employed to synthesize graphitic carbon nanosheets (GCNs) from Reactive Red 2, a common chemical pollutant in textile wastewater, for efficient tetracycline (TC) degradation via nonradical oxidation processes. Detailed physical characterization indicates that the GCN possesses a layered and flat structure, high microporosity, and microscopic configuration of graphene-like nanosheets with abundant surface O-, N- and S-containing functional groups (including graphitic N and carbonyl groups). From the kinetic model, quenching experiments and mechanism studies, only 1O2 is detected in the GCN/PMS system, without SO4˙−, HO˙ or O2˙−. 1O2 contributed to only 17.8% of overall TC degradation. Surface-confined electron transfer appears to be the major oxidation pathway (82.2%) for TC degradation. Furthermore, full-scale biological assays verify that the biotoxicity of the TC degradation products is significantly reduced in comparison with that of the precursor. This work provides a new insight toward the conversion from a chemical pollutant into a metal-free carbon catalyst for wastewater treatment.

Atom-precise nanoclusters-metal-organic framework (APNC/MOF) composites, as bifunctional material with well-defined structures, have attracted considerable attention in recent years. Despite the progress made to date, there is an urgent need to develop a generic and scalable approach for all APNCs. Herein, the authors present the Exploiting Fracture Strategy (EFS) and successfully construct a super-stable bifunctional APNC/ZIF-8(300 °C) composite overcoming the limitations of previous strategies in selecting APNCs. The EFS utilizes the fracture of ZnN in ZIF-8 after annealing at 300 °C. This method is suitable for all kinds of S/P protected APNCs with different sizes, including uncharged clusters Au

ConspectusProduction of hydrogen from nonfossil sources is essential toward the generation of sustainable energy. Hydrogen generation upon hydrolysis of stable hydrogen-rich materials has long been proposed as a possibility of hydrogen disposal on site, because transport of explosive hydrogen gas is dangerous. Hydrolysis of some boron derivatives could rapidly produce large amounts of hydrogen, but this requires the presence of very active catalysts. Indeed, late transition-metal nanocatalysts have recently been developed for the hydrolysis of a few hydrogen-rich precursors.Our research group has focused on the improvement and optimization of highly performing Earth-abundant transition-metal-based nanocatalysts, optimization of remarkable synergies between different metals in nanoalloys, supports including positive synergy with nanoparticles (NPs) for rapid hydrogen generation, comparison between various endo- or exoreceptors working as homogeneous and heterogeneous supports, mechanistic research, and comparison of the nanocatalyzed hydrolysis of several boron hydrides.First, hydrogen production upon hydrolysis of ammonia borane, AB (3 mol H2 per mol AB) was examined with heterogeneous endoreceptors. Thus, a highly performing Ni@ZIF-8 nanocatalyst was found to be superior over other Earth-abundant nanocatalysts and supports. With 85.7 molH2·molcat-1·min-1 at 25 °C, this Ni nanocatalyst surpassed the results of previous Earth-abundant nanocatalysts. The presence of NaOH accelerated the reaction, and a remarkable pH-dependent "on-off" control of the H2 production was established. Bimetallic nanoalloys Ni-Pt@ZIF-8 showed a dramatic volcano effect optimized with a nanoalloy containing 2/3 Ni and 1/3 Pt. The rate reached 600 molH2·molcat-1·min-1 and 2222 molH2·molPt-1·min-1 at 20 °C, which much overtook the performances of both related nanocatalysts Ni@ZIF-8 and Pt@ZIF-8. Next, hydrogen production was also researched via hydrolysis of sodium borohydride (4 mol H2 per mol NaBH4) using nanocatalysts in ZIF-8, and, among Earth-abundant nanocatalysts, Co@ZIF-8 showed the best performance, outperforming previous Co nanocatalysts. For exoreceptors, "click" dendrimers containing triazole ligands on their tripodal tethers were used as supports for homogeneous (semiheterogeneous) catalysis of both AB and NaBH4 hydrolysis. For both reactions, Co was found to be the best Earth-abundant metal, Pt the best noble metal, and Co1Pt1 the best nanoalloy, with synergistic effects. Based on kinetic measurements and kinetic isotope effects for all of these reactions, mechanisms are proposed and the hydrogen produced was further used in tandem reactions. Overall, dramatic triple synergies between these nanocatalyst components have allowed hydrogen release within a few seconds under ambient conditions. These nanocatalyst improvements and mechanistic findings should also inspire further nanocatalyst design in various areas of hydrogen production.

The search of new H₂ evolution systems avoiding fossil sources and their mechanisms is a priority in the 21st century society. Hydrolysis of tetrahydroxydiboron (TDB), a current borylation source in the literature, is used here for H₂ evolution for the first time. It is catalyzed by graphene quantum dot-stabilized nanoparticles (NPs). With RhNP- or PtNP-catalyzed reactions, D₂ formation from D₂O confirms that water is the only hydrogen source. Kinetic isotopic effects yield kH/kD = 5.91 and 4.18, strongly suggesting double water O–H bond cleavage on the NP surface in the rate-limiting step. The most efficient catalysts are the RhNP and PtNP (total turnover frequencies: 3658 and 4603 molH₂·molcₐₜ–¹·min–¹, respectively). The order of catalytic activity is as follows: PtNP > RhNP > AuNP > PdNP > IrNP > RuNP, and a catalytic mechanism of TDB hydrolysis is proposed.

Heterogeneous catalysts with precise surface and interface structures are of great interest to decipher the structure-property relationships and maintain remarkable stability while achieving high activity. Here, we report the design and fabrication of the new sandwich composites ZIF-8@Au25@ZIF-67[tkn] and ZIF-8@Au25@ZIF-8[tkn] [tkn = thickness of shell] by coordination-assisted self-assembly with well-defined structures and interfaces. The composites ZIF-8@Au25@ZIF-67 efficiently catalyzed both 4-nitrophenol reduction and terminal alkyne carboxylation with CO2 under ambient conditions with remarkably improved activity and stability, compared to the simple components Au25/ZIF-8 and Au25@ZIF-8, highlighting the highly useful function of the ultrathin shell. In addition, the performances of these composite sandwich catalysts are conveniently regulated by the shell thickness. This concept and achievements should open a new avenue to the targeted design of well-defined nanocatalysts with enhanced activities and stabilities for challenging reactions.

Ferrocene-containing polymers have been investigated for more than six decades, and more recently modern synthetic methods have allowed the fabrication of precise polymers that contain a variety of transition-metal complexes. Trends are now oriented towards applications, such as optics, energy conversion and storage, electrochemistry, magnetics, electric conductors and biomedicine. Metal-sandwich complexes such as those of ferrocene type and other related complexes that present redox-robust groups in polymers, i.e. that are isolable in both their oxidized and reduced forms, are of particular interest, because it is possible to address them using electronic or photonic redox stimuli for application. Our research groups have called such complexes Electron-Reservoirs and introduced them in the main chain or in the side chains of well-defined polymers. For instance, polymers with ferrocene in the main chain or in the side chain are oxidized to stable polycationic polyelectrolytes only if ferrocene is part of a biferrocene unit, because biferrocene oxidation leads to the biferrocenium cation that is stabilized by the mixed valency. Then a group of several redox-robust iron sandwich complexes were fabricated and incorporated in precise polymers including multi-block copolymers whose controlled synthesis and block incorporation was achieved for instance using ring-opening-metathesis polymerization. Applications of this family of Electron-Reservoir-containing polymers includes electrochemically induced derivatization of electrodes by decorating them with these polymers, molecular recognition and redox sensing, electrochromics with multiple colours, generation of gold and silver nanoparticles of various size by reduction of gold(iii) and silver(i) precursors and their use for nanocatalysis towards depollution and biomedicine.

International audience; Hydrogen (H2) formation from hydrogen-rich precursors is a hot topic, whereby carbon-free energy perspectives, mechanistic features, and synthetic applications are actively searched. Here, we report oxygen atom uptake from water under ambient conditions, producing H2 in the presence of alloyed Au-Rh nanoparticle catalysts encapsulated in a “click”-dendrimer. These systems are named nanozymes (NZs) because their function and mechanism resemble those of hydrogenase enzymes. The Au-Rh NZs with variable proportions of Au and Rh exhibit positive sharp volcano-type synergy and visible light-induced acceleration. The best synergy in the dark is disclosed in Au4Rh1, achieving a turnover frequency (TOFs) of 5100 molH2 molcata–1 min–1 in dark, 3.4 times higher than the related Au NZ and 8.9 times higher than the related Rh NZ at 25 ± 1 °C. The catalytic activity of Au-Rh for H2 evolution is enhanced by visible light irradiation due to the Au plasmon, so that the synergistic effect in the dark and the visible light-induced rate enhancement cumulate for Au4Rh1, allowing for complete B2(OH)4 hydrolysis in 39 s at 25 ± 1 °C (TOFs = 6000 molH2 molcata–1 min–1). Upon increasing the Rh content, Au-Rh provides less synergy in the dark, whereas the light enhancement of the reaction rate increases, reaching a maximum for Au1Rh2. Experiments using D2O, including kinetic isotope effect determination, suggest that the rate-determining step of the reaction involves concerted O–H bond cleavage of water and support the proposed catalytic reaction mechanism.

In this mini-review article the concept of electron reservoir materials developed in the author’s laboratory is summarized. Starting from mono- and bimetallic electron reservoir complexes and their electronic and catalytic properties this concept extends to macromolecular electron-reservoir devices including metallodendrimers, metallopolymers and macromolecule-stabilized late transition-metal nanoparticles. The electronic switch in these devices is discussed as well as the structure-dependent possibilities to stabilize both utilized redox forms. Catalytic and energy-related applications involving redox metallomacromolecules and nanoparticles and their potential extension are briefly discussed. Giant ferrocene and pentamethylferrocene-based dendrimers and polymers are typical electron reservoir macromolecules that have been isolated in both oxidized and reduced forms with the ability to carry a large flow of electrons at about the same potential. The dramatic structural and size changes of the metallomacromolecules upon redox switch is reminiscent of molecular machines.