6 research outputs found
Neutral-Type One-Dimensional Mixed-Valence Halogen-Bridged Platinum Chain Complexes with Large Charge-Transfer Band Gaps
One-dimensional (1D) electronic systems
have attracted significant attention for a long time because of their
various physical properties. Among 1D electronic systems, 1D halogen-bridged
mixed-valence transition-metal complexes (the so-called MX chains)
have been thoroughly studied owing to designable structures and electronic
states. Here, we report the syntheses, structures, and electronic
properties of three kinds of novel neutral MX-chain complexes. The
crystal structures consist of 1D chains of PtâX repeating units
with (1<i>R</i>,2<i>R</i>)-(â)-diaminocychlohexane
and CN<sup>â</sup> in-plane ligands. Because of the absence
of a counteranion, the neutral MX chains have short interchain distances,
so that strong interchain electronic interaction is expected. Resonance
Raman spectra and diffuse-reflectance UVâvis spectra indicate
that their electronic states are mixed-valence states (charge-density-wave
state: Pt<sup>2+</sup>···XâPt<sup>4+</sup>âX···Pt<sup>2+</sup>···XâPt<sup>4+</sup>âX···).
In addition, the relationship between the intervalence charge-transfer
(IVCT) band gap and the degree of distortion of the 1D chain shows
that the neutral MX chains have a larger IVCT band gap than that of
cationic MX-chain complexes. These results provide new insight into
the physical and electronic properties of 1D chain compounds
Single-Atom-Based Vanadium Oxide Catalysts Supported on MetalâOrganic Frameworks: Selective Alcohol Oxidation and StructureâActivity Relationship
We report the syntheses, structures,
and oxidation catalytic activities
of a single-atom-based vanadium oxide incorporated in two highly crystalline
MOFs, Hf-MOF-808 and Zr-NU-1000. These vanadium catalysts were introduced
by a postsynthetic metalation, and the resulting materials (Hf-MOF-808-V
and Zr-NU-1000-V) were thoroughly characterized through a combination
of analytic and spectroscopic techniques including single-crystal
X-ray crystallography. Their catalytic properties were investigated
using the oxidation of 4-methoxybenzyl alcohol under an oxygen atmosphere
as a model reaction. Crystallographic and variable-temperature spectroscopic
studies revealed that the incorporated vanadium in Hf-MOF-808-V changes
position with heat, which led to improved catalytic activity
Single-Atom Tailoring of the Electronic Structure of the Conductive Porous Coordination Polymer Enhances Efficient Electrochemical NH<sub>3</sub> Production
Conductive porous coordination polymers (PCPs) and metalâorganic
frameworks (MOFs) are promising candidates for electrocatalysts and
advanced electronic devices. Tailoring the electronic structure of
conductive PCPs/MOFs is crucial for achieving specific applications,
but it remains challenging. Herein, we introduce a novel approach
called the âsingle-atomâ strategy to tailor the electronic
structure of conductive PCPs/MOFs to enhance the electrocatalytic
performance for the reduction of nitrate to ammonia. By incorporating
atomically dispersed Ru3+ (at a content of about 5% per
Co) into semiconducting PCPs, we successfully created a highly efficient
PCP-based electrocatalyst named RuâCo-pyNDI, which exhibits
good structural stability and improved electrocatalytic performance.
The calculated and experimental results reveal that doping atomically
dispersed Ru3+ into Co-pyNDI induces local structural distortion,
resulting in a downshift of the d-band center of the Co, which in
turn facilitates the desorption of intermediates. As a result, the
RuâCo-pyNDI catalyst demonstrates superior electrocatalytic
performance in NH3 production compared to other heterogeneous
catalysts, achieving a high Faradaic efficiency of about 97% and an
ammonia yield rate of 12010 ÎŒg hâ1 mgcat.â1 (0.28 mmol hâ1 cmâ2) under neutral aqueous conditions
MetalâOrganic Framework with Structural Flexibility Responding Specifically to Acetylene and Its Adsorption Behavior
Flexible
metalâorganic frameworks (MOFs) are one
kind of
stimuli-responsive materials that exhibit reversible structural transformations
in response to external stimuli. Exploring and understanding the stimuli
response behavior of flexible MOFs is challenging, as it involves
weak hostâguest interaction. We report here the unique flexibility
of MOF Zn(int)(Ad) (TIF-A1, Hint = isonicotinic acid, Had = adenine)
induced by acetylene adsorption. TIF-A1 is rigid toward most gas molecules,
while only C2H2 can induce the flexibility of
TIF-A1. C2H2-loaded TIF-A1 is characterized
by single-crystal X-ray diffraction and molecular modeling. It is
revealed that the flexibility of TIF-A1 originates from the strong
interaction between acetylene and the framework, which pushes the
rotation of the int ligand and the expansion of the framework simultaneously.
This work is helpful in deeply understanding the flexibility of MOFs
and guides exploring new flexible MOFs in the future
MetalâOrganic Framework with Structural Flexibility Responding Specifically to Acetylene and Its Adsorption Behavior
Flexible
metalâorganic frameworks (MOFs) are one
kind of
stimuli-responsive materials that exhibit reversible structural transformations
in response to external stimuli. Exploring and understanding the stimuli
response behavior of flexible MOFs is challenging, as it involves
weak hostâguest interaction. We report here the unique flexibility
of MOF Zn(int)(Ad) (TIF-A1, Hint = isonicotinic acid, Had = adenine)
induced by acetylene adsorption. TIF-A1 is rigid toward most gas molecules,
while only C2H2 can induce the flexibility of
TIF-A1. C2H2-loaded TIF-A1 is characterized
by single-crystal X-ray diffraction and molecular modeling. It is
revealed that the flexibility of TIF-A1 originates from the strong
interaction between acetylene and the framework, which pushes the
rotation of the int ligand and the expansion of the framework simultaneously.
This work is helpful in deeply understanding the flexibility of MOFs
and guides exploring new flexible MOFs in the future
MOFâThermogel Composites for Differentiated and Sustained Dual Drug Delivery
In recent years, multidrug therapy has gained increasing
popularity
due to the possibility of achieving synergistic drug action and sequential
delivery of different medical payloads for enhanced treatment efficacy.
While a number of composite material release platforms have been developed,
few combine the bottom-up design versatility of metalâorganic
frameworks (MOFs) to tailor drug release behavior, with the convenience
of temperature-responsive hydrogels (or thermogels) in their unique
ease of administration and formulation. Yet, despite their potential,
MOFâthermogel composites have been largely overlooked for simultaneous
multidrug delivery. Herein, we report the first systematic study of
common MOFs (UiO-66, MIL-53(Al), MIL-100(Fe), and MOF-808) with different
pore sizes, geometries, and hydrophobicities for their ability to
achieve simultaneous dual drug release when embedded within PEG-containing
thermogel matrices. After establishing that MOFs exert small influences
on the rheological properties of the thermogels despite the penetration
of polymers into the MOF pores in solution, the release profiles of
ibuprofen and caffeine as model hydrophobic and hydrophilic drugs,
respectively, from MOFâthermogel composites were investigated.
Through these studies, we elucidated the important role of hydrophobic
matching between MOF pores and loaded drugs in order for the MOF component
to distinctly influence drug release kinetics. These findings enabled
us to identify a viable MOFâthermogel composite containing
UiO-66 that showed vastly different release kinetics between ibuprofen
and caffeine, enabling temporally differentiated yet sustained simultaneous
drug release to be achieved. Finally, the MOFâthermogel composites
were shown to be noncytotoxic in vitro, paving the way for these underexploited
composite materials to find possible clinical applications for multidrug
therapy