5 research outputs found
Stabilizing a three-center single-electron metal–metal bond in a fullerene cage
Trimetallic carbide clusterfullerenes (TCCFs) encapsulating a quinary M3C2 cluster represent a special family of endohedral fullerenes with an open-shell electronic configuration. Herein, a novel TCCF based on a medium-sized rare earth metal, dysprosium (Dy), is synthesized for the first time. The molecular structure of Dy3C2@Ih(7)-C80 determined by single crystal X-ray diffraction shows that the encapsulated Dy3C2 cluster adopts a bat ray configuration, in which the acetylide unit C2 is elevated above the Dy3 plane by ∼1.66 Å, while Dy–Dy distances are ∼3.4 Å. DFT computational analysis of the electronic structure reveals that the endohedral cluster has an unusual formal charge distribution of (Dy3)8+(C2)2−@C806− and features an unprecedented three-center single-electron Dy–Dy–Dy bond, which has never been reported for lanthanide compounds. Moreover, this electronic structure is different from that of the analogous Sc3C2@Ih(7)-C80 with a (Sc3)9+(C2)3−@C806− charge distribution and no metal–metal bonding
Tuning the Coordination Environment of Carbon-Based Single-Atom Catalysts via Doping with Multiple Heteroatoms and Their Applications in Electrocatalysis
Carbon-based single-atom catalysts (SACs) are considered to be a perfect platform for studying the structure-activity relationship of different reactions due to the adjustability of their coordination environment. Multi-heteroatom doping has been demonstrated as an effective strategy for tuning the coordination environment of carbon-based SACs and enhancing catalytic performance in electrochemical reactions. Herein, recently developed strategies for multi-heteroatom doping, focusing on the regulation of single-atom active sites by heteroatoms in different coordination shells, are summarized. In addition, the correlation between the coordination environment and the catalytic activity of carbon-based SACs are investigated through representative experiments and theoretical calculations for various electrochemical reactions. Finally, concerning certain shortcomings of the current strategies of doping multi-heteroatoms, some suggestions are put forward to promote the development of carbon-based SACs in the field of electrocatalysis
Asymmetric Aerogel Membranes with Ultrafast Water Permeation for the Separation of Oil-in-Water Emulsion
Owing
to highly porous and low density attributes, aerogels have
been actively utilized in catalysis and adsorption processes, but
their great potential in filtration requires exploitation. In this
study, an asymmetric aerogel membrane is fabricated via one-pot hydrothermal
reaction-induced self-cross-linking of poly(vinyl alcohol) (PVA),
which exhibits ultrafast permeation for the separation of oil-in-water
emulsion. Meanwhile, carbon nanotubes are added to improve the mechanical
strength of the aerogel membranes. The self-cross-linking of PVA forms
the supporting layer, and the exchange of water and vapor at the interface
of PVA solution and air generates the separating layer as well as
abundant hydroxyl groups on the membrane surface. The density, porosity,
pore size, and wettability of the aerogel membrane can be tuned by
the PVA concentration. Owing to high porosity (>95%) and suitable
pore size (<85 nm), the aerogel membrane exhibits high rejection
(99.0%) for surfactant-stabilized oil-in-water emulsion with an ultrahigh
permeation flux of 135.5 × 10<sup>3</sup> L m<sup>–2</sup> h<sup>–1</sup> bar<sup>–1</sup> under gravity-driven
flow, which is 2 orders of magnitude higher than commercial filtration
membranes with similar rejection. Meanwhile, the aerogel membrane
exhibits superhydrophilicity, superoleophobicity underwater, and excellent
antifouling properties for various surfactant-stabilized oil-in-water
emulsions, as indicated by the fact that the flux recovery ratio maintains
more than 93% after five cycles of the filtration experiment. The
findings in this study may offer a novel idea to fabricate high-throughput
filtration membranes