2 research outputs found
MOF-Templated Fabrication of Hollow Co<sub>4</sub>N@N-Doped Carbon Porous Nanocages with Superior Catalytic Activity
Metallic
Co<sub>4</sub>N catalysts have been considered as one of the most
promising non-noble materials for heterogeneous catalysis because
of their high electrical conductivity, great magnetic property, and
high intrinsic activity. However, the metastable properties seriously
limit their applications for heterogeneous water phase catalysis.
In this work, a novel Co-metal–organic framework (MOF)-derived
hollow porous nanocages (PNCs) composed of metallic Co<sub>4</sub>N and N-doped carbon (NC) were synthesized for the first time. This
hollow three-dimensional (3D) PNC catalyst was synthesized by taking
advantage of Co-MOF as a precursor for fabricating 3D hollow Co<sub>3</sub>O<sub>4</sub>@C PNCs, along with the NH<sub>3</sub> treatment
of Co-oxide frames to promote the in situ conversion of Co-MOF to
Co<sub>4</sub>N@NC PNCs, benefiting from the high intrinsic activity
and electron conductivity of the metallic Co<sub>4</sub>N phase and
the good permeability of the hollow porous nanostructure as well as
the efficient doping of N into the carbon layer. Besides, the covalent
bridge between the active Co<sub>4</sub>N surface and PNC shells also
provides facile pathways for electron and mass transport. The obtained
Co<sub>4</sub>N@NC PNCs exhibit excellent catalytic activity and stability
for 4-nitrophenol reduction in terms of low activation energy (<i>E</i><sub>a</sub> = 23.53 kJ mol<sup>–1</sup>), high
turnover frequency (52.01 × 10<sup>20</sup> molecule g<sup>–1</sup> min<sup>–1</sup>), and high apparent rate constant (<i>k</i><sub>app</sub> = 2.106 min<sup>–1</sup>). Furthermore,
its magnetic property and stable configuration account for the excellent
recyclability of the catalyst. It is hoped that our finding could
pave the way for the construction of other hollow transition metal-based
nitride@NC PNC catalysts for wide applications
Ferrocenoyl Phenylalanine: A New Strategy Toward Supramolecular Hydrogels with Multistimuli Responsive Properties
In
this paper we present a new paradigm for designing hydrogelators
that exhibit sharp phase transitions in response to a series of disparate
stimuli, including oxidation–reduction reactions (redox), guest–host
interactions, and pH changes. We have serendipitously discovered that
ferrocenoyl phenylalanine (Fc-F) monomers aggregate in water via a
rapid self-assembly mechanism to form stable, multistimuli hydrogels.
In comparison to other known mono- and multiresponsive gelators, Fc-F
is unique because of its small size, economy of gel-forming components,
and exceptionally simple molecular structure. Density functional theory
(DFT) <i>ab initio</i> calculations suggest gel formation
initially involves an antiparallel, noncovalent dimerization step
wherein the ferrocenoyl moiety of one axe-like monomer conjoins with
the phenyl group of the second monomer via a π–π
stacking interaction to form brick-like dimers. This stacking creates
a cavity in which the carboxylic acid groups of each monomer mutually
interact via hydrogen bond formation, which affords additional stability
to the dimer. On the basis of structural analysis via optical and
electrical measurements and additional DFT calculations, we propose
a possible stepwise hierachical assembly mechanism for fibril formation.
Insights into the self-assembly pathway of Fc-F should prove useful
for understanding gelation processes of more complex systems. We expect
that Fc-F will serve as a helpful archetypical template for others
to use when designing new, stimuli specific hydrogelation agents