A unique approach for the synthesis of nonstoichiometric, mesoporous molybdenum oxide (MoO 3-x ) with nanosized crystalline walls by using a soft template (PEO-b -PS) synthesis method is introduced. The as-synthesized mesoporous MoO 3-x is very active and stable (durability > 12 h) for the electrochemical hydrogen evolution reaction (HER) under both acidic and alkaline conditions. The intrinsic MoO 3 serves as an HER electrocatalyst without the assistance of carbon materials, noble metals, or MoS 2 materials. The results from transmission electron microscopy and N 2 sorption techniques show that the as-synthesized mesoporous MoO 3-x has large accessible pores (20-40 nm), which are able to facilitate mass transport and charge transfer during HER. In terms of X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed oxidation, and diffusive refl ectance UV-vis spectroscopy, the mesoporous MoO 3-x exhibits mixed oxidation states (Mo 5+ , Mo 6+ ) and an oxygen-defi cient structure. The as-synthesized MoO 3-x only requires a low overpotential (≈0.14 V) to achieve a 10 mA cm −2 current density in 0.1 M KOH and the Tafel slope is as low as 56 mV dec −1 . Density functional theory calculations demonstrate a change of electronic structure and the possible reaction pathway of HER. Oxygen vacancies and mesoporosity serve as key factors for excellent performance.

New fluorochromic materials that reversibly change their emission properties in response to their environment are of interest for the development of sensors and light-emitting materials. A new design of Eu-containing polymer hydrogels showing fast self-healing and tunable fluorochromic properties in response to five different stimuli, including pH, temperature, metal ions, sonication, and force, is reported. The polymer hydrogels are fabricated using Eu-iminodiacetate (IDA) coordination in a hydrophilic poly(N,N-dimethylacrylamide) matrix. Dynamic metal-ligand coordination allows reversible formation and disruption of hydrogel networks under various stimuli which makes hydrogels self-healable and injectable. Such hydrogels show interesting switchable ON/OFF luminescence along with the sol-gel transition through the reversible formation and dissociation of Eu-IDA complexes upon various stimuli. It is demonstrated that Eu-containing hydrogels display fast and reversible mechanochromic response as well in hydrogels having interpenetrating polymer network. Those multistimuli responsive fluorochromic hydrogels illustrate a new pathway to make smart optical materials, particularly for biological sensors where multistimuli response is required.

CO2‐Reduktion. Polymere NHC‐Liganden verbessern die Katalyseeffizienz und Lebensdauer von Au‐ und Pd‐Nanokatalysatoren zur CO2‐Elektroreduktion, wie B. Liu, J. He et al. im Forschungsartikel auf S. 15981 ff. zeigen.

This Communication highlights the facet-dependent electrocatalytic activity of MnO nanocrystals for OERs/ORRs. The MnO(100) facets with higher adsorption energy of O species can largely promote the electrocatalytic activity.

Nano building blocks (NBBs) decorated with well-defined polymer tethers have emerged as a promising type of building blocks for constructing hierarchical materials through programmable self-assembly. We present a general and facile strategy for preparing hybrid NBBs composed of silica-like heads decorated with well-defined polymer tethers by the self-collapse of polymer single chains. Using amphiphilic block copolymers (BCPs) of poly(ethylene oxide)-block-[poly(methyl methacrylate)-co-poly(3-(trimethoxysilyl)propyl methacrylate)] (PEO-b-P(MMA-co-TMSPMA)), the intramolecular hydrolysis and polycondensation of silane moieties led to the formation of hybrid NBBs with silica-like heads and PEO tethers. The formation of hybrid NBBs was carefully characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, transmission electron microscopy, and static/dynamic light scattering. In a mixed solvent of THF/water, amphiphilic NBBs could assemble into spherical micelles, vesicles, and large compound micelles, depending on the size of silica heads and the initial concentrations. The intramolecular cross-linking of P(MMA-co-TMSPMA) blocks significantly altered the assembly behavior of linear BCPs. The rigid hydrophobic heads of NBBs could not be stretched/compressed, and the selfassembly of NBBs behaved surfactant-like. Furthermore, we observed that the mismatched dimensions of NBBs and linear BCPs would give rise to the formation of unprecedented phase-separated bilayer vesicles when coassembling two amphiphiles. Our study of NBBs may bridge the study of nanoparticles and polymeric building blocks and offer new opportunities to synthesize hybrid NBBs with controlled functionalities for use in novel functional materials and devices.

A bottom-up synthetic approach was developed for the preparation of mesoporous transition-metal-oxide/noble-metal hybrid catalysts through ligand-assisted co-assembly of amphiphilic block-copolymer micelles and polymer-tethered noble-metal nanoparticles (NPs). The synthetic approach offers a general and straightforward method to precisely tune the sizes and loadings of noble-metal NPs in metal oxides. This system thus provides a solid platform to clearly understand the role of noble-metal NPs in photochemical water splitting. The presence of trace amounts of metal NPs (≈0.1 wt %) can enhance the photocatalytic activity for water splitting up to a factor of four. The findings can conceivably be applied to other semiconductors/noble-metal catalysts, which may stand out as a new methodology to build highly efficient solar energy conversion systems.

Metal-containing single chain polymeric nanoparticles (SCPNs) can be used as synthetic mimics of metalloenzymes. Currently, the role of the folded polymer backbones on the activity and selectivity of metal sites is not clear. Herein, we report our findings on how polymeric frameworks modulate the coordination of Cu sites and the catalytic activity/selectivity of Cu-containing SCPNs mimicking monophenol hydroxylation reactions. Imidazole-functionalized copolymers of poly­(methyl methacrylate-co-3-imidazolyl-2-hydroxy propyl methacrylate) were used for intramolecular Cu-imidazole binding that triggered the self-folding of polymers. Polymer chains imposed steric hindrance which yielded unsaturated Cu sites with an average coordination number of 3.3. Cu-containing SCPNs showed a high selectivity for the hydroxylation reaction of phenol to catechol, >80%, with a turnover frequency of >870 h–1 at 60 °C. The selectivity was largely influenced by the flexibility of the folded polymer backbone where a more flexible polymer backbone allows the cooperative catalysis of two Cu sites. The second coordination sphere provided by the folded polymer that has been less studied is therefore critical in the design of active mimics of metalloenzymes.

New synthetic methods capable of controlling structural and compositional complexities of asymmetric nanoparticles (NPs) are very challenging but highly desired. A simple and general synthetic approach to designing sophisticated asymmetric NPs by anisotropically patterning the surface of isotropic metallic NPs with amphiphilic block copolymers (BCPs) is reported. The selective galvanic replacement and seed-mediated growth of a second metal can be achieved on the exposed surface of metal NPs, resulting in the formation of nanobowls and Janus-type metal-metal dimers, respectively. Using Ag and Au NPs tethered with amphiphilic block copolymers of poly(ethylene oxide)-block-polystyrene (PEO-b-PS), anisotropic surface patterning of metallic NPs (e.g., Ag and Au) is shown to be driven by thermodynamical phase segregation of BCP ligands on isotropic metal NPs. Two proof-of-concept experiments are given on, i) synthesis of Au nanobowls by a selective galvanic replacement reaction on Janus-type patched Ag/polymer NPs; and ii) preparation of Au-Pd heterodimers and Au-Au homodimers by a seed-mediated growth on Janus-type patched Au/polymer NPs. The method shows remarkable versatility; and it can be easily handled in aqueous solution. This synthetic strategy stands out as the new methodology to design and synthesis asymmetric metal NPs with sophisticated topologies.