Zeolitic Imidazolate Frameworks as Solid-State Nanomachines.

Machines have continually developed with the needs of daily life and industrial applications. While the careful design of molecular-scale devices often displays enhanced properties along with mechanical movements, controlling mechanics within solid-state molecular structures remains a significant challenge. Here, we explore the distinct mechanical properties of zeolitic imidazolate frameworks (ZIFs)-frameworks that contain hidden mechanical components. Using a combination of experimental and theoretical approaches, we uncover the machine-like capabilities of ZIFs, wherein connected composite building units operate similarly to a mechanical linkage system. Importantly, this research suggests that certain ZIF subunits act as core mechanical components, paving an innovative view for the future design of solid-state molecular machines.

Origamic metal-organic framework toward mechanical metamaterial.

Origami, known as paper folding has become a fascinating research topic recently. Origami-inspired materials often establish mechanical properties that are difficult to achieve in conventional materials. However, the materials based on origami tessellation at the molecular level have been significantly underexplored. Herein, we report a two-dimensional (2D) porphyrinic metal-organic framework (MOF), self-assembled from Zn nodes and flexible porphyrin linkers, displaying folding motions based on origami tessellation. A combined experimental and theoretical investigation demonstrated the origami mechanism of the 2D porphyrinic MOF, whereby the flexible linker acts as a pivoting point. The discovery of the 2D tessellation hidden in the 2D MOF unveils origami mechanics at the molecular level.

Protein-Precoated Surface of Metal-Organic Framework Nanoparticles for Targeted Delivery.

Metal-organic framework (MOF) nanoparticles have recently emerged as a promising vehicle for drug delivery with high porosity and feasibility. However, employing a MOF-based drug delivery system remains a challenge due to the difficulty in controlling interfaces of particles in a biological environment. In this paper, protein corona-blocked Zr6 -based MOF (PCN-224) nanoparticles are presented for targeted cancer therapy with high efficiency. The unmodified PCN-224 surface is precoated with glutathione transferase (GST)-fused targetable affibody (GST-Afb) proteins via simple mixing conjugations instead of chemical modifications that can induce the impairment of proteins. GST-Afb proteins are shown to stably protect the surface of PCN-224 particles in a specific orientation with GST adsorbed onto the porous surface and the GST-linked Afb posed outward, minimizing the unwanted interfacial interactions of particles with external biological proteins. The Afb-directed cell-specific targeting ability of particles and consequent induction of cell death is demonstrated both in vitro and in vivo by using two kinds of Afb, which targets the surface membrane receptor, human epidermal growth factor receptor 2 (HER2) or epidermal growth factor receptor (EGFR). This study provides insight into the way of regulating the protein-adhesive surface of MOF nanoparticles and designing a more effective MOF-hosted targeted delivery system.

PN-Doped tetraphenylnaphthalene: a straightforward synthetic strategy analogous to BN-annulation.

Compared to BN heterocycles, few studies on PN heterocycles have been reported to date. Herein, we developed an efficient synthetic strategy analogous to BN-annulation to simultaneously incorporate a PN bond and a halogen group into the naphthalene core. Subsequently, we prepared PN-containing tetraphenylnaphthalene using this method, followed by palladium-catalyzed cross-coupling and reduction reactions. The prepared molecule was characterized via X-ray crystallography, NMR spectroscopy, UV-vis spectroscopy, and cyclic voltammetry.

Impact of Zr6 Node in a Metal-Organic Framework for Adsorptive Removal of Antibiotics from Water.

Quinolone-based antibiotics commonly detected in surface, ground, and drinking water are difficult to remove and therefore pose a threat as organic contaminants of aqueous environment. We performed adsorptive removal of quinolone antibiotics, nalidixic acid and ofloxacin, using a zirconium-porphyrin-based metal-organic framework (MOF), PCN-224. PCN-224 exhibits the highest adsorption capacities for both nalidixic acid and ofloxacin among those reported for MOFs to date. The accessible metal sites of Zr metal nodes are responsible for efficient adsorptive removal. This study offers a pragmatic approach to design MOFs optimized for adsorptive removal of antibiotics.

Role of Zr6 Metal Nodes in Zr-Based Metal-Organic Frameworks for Catalytic Detoxification of Pesticides.

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.

Bisindole alkaloids from Voacanga grandifolia leaves.

Two new bisindole alkaloids, 12'-O-demethyl-vobtusine-5-lactam and isovobtusine-N-oxide (1 and 2), were isolated from the leaves of Voacanga grandifolia, together with two known bisindole alkaloids. Their structures were elucidated on the basis of 1D and 2D NMR data. 1 and 2 showed potent antimalarial activity against Plasmodium falciparum 3D7 and very low cytotoxic activity against a human cell line, HepG2 cells.

Unveiling 79-Year-Old Ixene and Its BN-Doped Derivative.

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 (B2 N2 -ixene), and their characterizations. Compared to ixene, B2 N2 -ixene absorbs longer-wavelength light and has a smaller electrochemical energy gap. In addition to its single-crystal structure, scanning tunneling microscopy revealed that B2 N2 -ixene adopts a nonplanar geometry on a Au(111) surface. The experimentally obtained electronic structure of B2 N2 -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.

MOF × Biopolymer: Collaborative Combination of Metal-Organic Framework and Biopolymer for Advanced Anticancer Therapy.

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.

Metal-organic framework based on hinged cube tessellation as transformable mechanical metamaterial.

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.