Metal–organic
framework (MOF) nanoparticles with
high porosity and greater tunability have emerged as new drug delivery
vehicles. However, premature drug release still remains a challenge
in the MOF delivery system. Here, we report an enzyme-responsive,
polymer-coated MOF gatekeeper system using hyaluronic acid (HA) and
PCN-224 nanoMOF. The external surface of nanoMOF can be stably covered
by HA through multivalent coordination bonding between the Zr cluster
and carboxylic acid of HA, which
acts as a gatekeeper. HA allows selective accumulation of drug carriers
in CD44 overexpressed cancer cells and enzyme-responsive drug release
in
the cancer cell environment. In particular, inherent characteristics
of PCN-224, which is used as a drug carrier, facilitates the transfer
of the drug to cancer cells more stably and allows photodynamic therapy.
This HA-PCN system enables a dual chemo and photodynamic therapy
to enhance the cancer therapy effect.
Mechanical metamaterials exhibit unusual properties, such as negative Poisson’s ratio, which are difficult to achieve in conventional materials. Rational design of mechanical metamaterials at the microscale is becoming popular partly because of the advance in three-dimensional printing technologies. However, incorporating movable building blocks inside solids, thereby enabling us to manipulate mechanical movement at the molecular scale, has been a difficult task. Here, we report a metal-organic framework, self-assembled from a porphyrin linker and a new type of Zn-based secondary building unit, serving as a joint in a hinged cube tessellation. Detailed structural analysis and theoretical calculation show that this material is a mechanical metamaterial exhibiting auxetic behavior. This work demonstrates that the topology of the framework and flexible hinges inside the structure are intimately related to the mechanical properties of the material, providing a guideline for the rational design of mechanically responsive metal-organic frameworks.
Pesticides are chemicals widely used
for agricultural industry,
despite their negative impact on health and environment. Although
various methods have been developed for pesticide degradation to remedy
such adverse effects, conventional materials often take hours to days
for complete decomposition and are difficult to recycle. Here, we
demonstrate the rapid degradation of organophosphate pesticides with
a Zr-based metal–organic framework (MOF), showing complete
degradation within 15 min. MOFs with different active site structures
(Zr node connectivity and geometry) were compared, and a porphyrin-based
MOF with six-connected Zr nodes showed remarkable degradation efficiency
with half-lives of a few minutes. Such a high efficiency was further
confirmed in a simple flow system for several cycles. This study reveals
that MOFs can be highly potent heterogeneous catalysts for organophosphate
pesticide degradation, suggesting that coordination geometry of the
Zr node significantly influences the catalytic activity.
Polycyclic aromatic hydrocarbons (PAHs) are key components of organic electronics. The electronic properties of these carbon‐rich materials can be controlled through doping with heteroatoms such as B and N, however, few convenient syntheses of BN‐doped PAHs have been reported. Described herein is the rationally designed, two‐step syntheses of previously unknown ixene and BN‐doped ixene (B2N2‐ixene), and their characterizations. Compared to ixene, B2N2‐ixene absorbs longer‐wavelength light and has a smaller electrochemical energy gap. In addition to its single‐crystal structure, scanning tunneling microscopy revealed that B2N2‐ixene adopts a nonplanar geometry on a Au(111) surface. The experimentally obtained electronic structure of B2N2‐ixene and the effect of BN‐doping were confirmed by DFT calculations. This synthesis enables the efficient and convenient construction of BN‐doped systems with extended π‐conjugation that can be used in versatile organic electronics applications.
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