Rabies Virus‐Inspired Metal–Organic Frameworks (MOFs) for Targeted Imaging and Chemotherapy of Glioma

The blood–brain barrier (BBB) restricts access to the brain of more than 98 % of therapeutic agents and is largely responsible for treatment failure of glioblastoma multiforme (GBM). Therefore, it is of great importance to develop a safe and efficient strategy for more effective drug delivery across the BBB into the brain. Inspired by the extraordinary capability of rabies virus (RABV) to enter the central nervous system, we report the development and evaluation of the metal–organic framework‐based nanocarrier MILB@LR, which closely mimicked both the bullet‐shape structure and surface functions of natural RABV. MILB@LR benefited from a more comprehensive RABV‐mimic strategy than mimicking individual features of RABV and exhibited significantly enhanced BBB penetration and brain tumor targeting. MILB@LR also displayed superior inhibition of tumor growth when loaded with oxaliplatin. The results demonstrated that MILB@LR may be valuable for GBM targeting and treatment.     

Sequential Transformation of Zirconium(IV)‐MOFs into Heterobimetallic MOFs Bearing Magnetic Anisotropic Cobalt(II) Centers

Heterometallic metal–organic frameworks (MOFs) allow the precise placement of various metals at atomic precision within a porous framework. This new level of control by MOFs promises fascinating advances in basic science and application. However, the rational design and synthesis of heterometallic MOFs remains a challenge due to the complexity of the heterometallic systems. Herein, we show that bimetallic MOFs with MX₂(INA)₄ moieties (INA=isonicotinate; M=Co²⁺ or Fe²⁺; X=OH^?, Cl^?, Br^?, I^?, NCS^?, or NCSe^?) can be generated by the sequential modification of a Zr‐based MOF. This multi‐step modification not only replaced the linear organic linker with a square planar MX₂(INA)₄ unit, but also altered the symmetry, unit cell, and topology of the parent structure. Single‐crystal to single‐crystal transformation is realized so that snapshots for transition process were captured by successive single‐crystal X‐ray diffraction. Furthermore, the installation of Co(NCS)₂(INA)₄ endows field‐induced slow magnetic relaxation property to the diamagnetic Zr‐MOF.     

Monomolecular sheets of propeller‐shaped triethyl 4,4′,4′′‐[benzene‐1,3,5‐triyltris(ethyne‐2,1‐diyl)]tribenzoate deuterochloroform monosolvate

The title compound, C₃₉H₃₀O₆·CDCl₃, has a chemical threefold axis and an approximately planar structure, with an ethoxycarbonyl substituent on each of the terminal benzenes oriented in the same direction, thus forming a propeller‐shaped molecule. This molecule is of particular interest in the field of metal–organic frameworks (MOFs), where its hydrolyzed analogue forms MOF structures with high surface areas. The benzene ring which occupies the centre of the molecule forms π–π interactions to the equivalent benzene ring at a perpendicular distance of 3.32 (1) Å. Centrosymmetric dimers formed in this way are interconnected by intermolecular C—H...π interactions with a rather short H...CgA distance of 2.51 Å (CgA is the centroid of the central benzene ring). The molecules are arranged in regular parallel sheets. Within a sheet, molecules are interconnected via C—H...O interactions where all carbonyl O atoms participate in weak hydrogen bonds as hydrogen‐bond acceptors. Neighbouring sheets are connected through the above‐mentioned π–π and C—H...π interactions.     

Hollow Zn/Co ZIF Particles Derived from Core–Shell ZIF‐67@ZIF‐8 as Selective Catalyst for the Semi‐Hydrogenation of Acetylene

The rational design of metal–organic frameworks (MOFs) with hollow features and tunable porosity at the nanoscale can enhance their intrinsic properties and stimulates increasing attentions. In this Communication, we demonstrate that methanol can affect the coordination mode of ZIF‐67 in the presence of Co²⁺ and induces a mild phase transformation under solvothermal conditions. By applying this transformation process to the ZIF‐67@ZIF‐8 core–shell structures, a well‐defined hollow Zn/Co ZIF rhombic dodecahedron can be obtained. The manufacturing of hollow MOFs enables us to prepare a noble metal@MOF yolk‐shell composite with controlled spatial distribution and morphology. The enhanced gas storage and porous confinement that originate from the hollow interior and coating of ZIF‐8 confers this unique catalyst with superior activity and selectivity toward the semi‐hydrogenation of acetylene.     

Aqueous‐Phase Synthesis of Mesoporous Zr‐Based MOFs Templated by Amphoteric Surfactants

Zr‐based mesoporous metal–organic frameworks (mesoMOFs) with uniform mesochannels and crystallized microporous framework were constructed in a water‐based system using amphoteric surfactants as templates. Aqueous‐phase synthesis guaranteed the formation of rod‐shaped surfactant micelles. Meanwhile, the carboxylate groups of amphoteric surfactants provided the anchoring to bridge Zr‐oxo clusters and surfactant assemblies. As a result, the directed crystallization of MOFs proceeded around cylindrical micelles and the hierarchical micro‐ and mesostructure was produced. The dimensions of mesopores were easily tailored by changing the alkyl chain length of the applied surfactants. The included surfactant was effectively extracted thanks to the exceptional stability of the obtained Zr‐based mesoMOFs. The almost complete occupation of the mesopore by cytochrome c exemplifies the accessibility of the mesochannels, suggesting the potential applications of the obtained mesoMOFs with bulky molecules.     

Evidence of Amine–CO2 Interactions in Two Pillared‐Layer MOFs Probed by X‐ray Crystallography

Two pillared‐layer metal–organic frameworks (MOFs; PMOF‐55 and NH₂‐PMOF‐55) based on 1,2,4‐triazole and terephthalic acid (bdc)/NH₂‐bdc ligands were assembled and display framework stabilities, to a certain degree, in both acid/alkaline solutions and toward water. They exhibit high CO₂ uptakes and selective CO₂/N₂ adsorption capacities, with CO₂/N₂ selectivity in the range of 24–27, as calculated by the ideal adsorbed solution theory method. More remarkably, the site and interactions between the host network and the CO₂ molecules were investigated by single‐crystal X‐ray diffraction, which showed that the main interaction between the CO₂ molecules and PMOF‐55 is due to multipoint supramolecular interactions of C?H???O, C???O, and O???O. Amino functional groups were shown to enhance the CO₂ adsorption and identified as strong adsorption sites for CO₂ by X‐ray crystallography.     

Hollow Metal–Organic‐Framework‐Mediated In Situ Architecture of Copper Dendrites for Enhanced CO2 Electroreduction

Electrocatalytic reduction of CO₂ to a single product at high current densities and efficiencies remains a challenge. However, the conventional electrode preparation methods, such as drop‐casting, usually suffer from low intrinsic activity. Herein, we report a synthesis strategy for preparing heterogeneous electrocatalyst composed of 3D hierarchical Cu dendrites that derived from an in situ electrosynthesized hollow copper metal–organic framework (MOF), for which the preparation of the Cu‐MOF film took only 5 min. The synthesis strategy preferentially exposes active sites, which favor's the reduction of CO₂ to formate. The current density could be as high as 102.1 mA cm^?2 with a selectivity of 98.2 % in ionic‐liquid‐based electrolyte and a commonly used H‐type cell.     

Systematic Investigation of High‐Sensitivity Luminescent Sensing for Polyoxometalates and Iron(III) by MOFs Assembled with a New Resorcin[4]arene‐Functionalized Tetracarboxylate

A new family of resorcin[4]arene‐based metal–organic frameworks (MOFs), namely, [Eu(HL)(DMF)(H₂O)₂] ? 3 H₂O ( 1 ), [Tb(HL)(DMF)(H₂O)₂] 3 H₂O ( 2 ), [Cd₄(L)₂(DMF)₄(H₂O)₂] 3 H₂O ( 3 ) and [Zn₃(HL)₂(H₂O)₂] 2 DMF ? 7 H₂O ( 4 ), have been constructed from a new resorcin[4]arene‐functionalized tetracarboxylic acid (H₄L=2,8,14,20‐tetra‐ethyl‐6,12,18,24‐tetra‐methoxy‐4,10,16,22‐tetra‐carboxy‐methoxy‐calix[4]arene). Isostructural 1 and 2 exhibit charming 1D motifs built with the cup‐like HL^3? anions and rare earth cations. Compounds 3 and 4 show a unique sandwich‐based 2D layer and a fascinating 3D framework, respectively. Remarkably, compounds 1 and 2 display intensive red and green emissions triggered by the efficient antenna effect of organic ligands under UV light. More importantly, systematic luminescence studies demonstrate that Ln‐MOFs 1 and 2 , as efficient multifunctional fluorescent materials, show highly selective and sensitive sensing of Fe³⁺, polyoxometalates (POMs), and acetone, which represents a rare example of a sensor for quantitatively detecting three different types of analytes. This is also an exceedingly rare example of Fe³⁺ and POMs detection in aqueous solutions employing resorcin[4]arene‐based luminescent Ln‐MOFs. Furthermore, the possible mechanism of the sensing properties is deduced.     

Impact of the Nature of the Organic Spacer on the Crystallization Kinetics of UiO‐66(Zr)‐Type MOFs

The influence of the constitutive dicarboxylate linkers (size, functional group) over the crystallization kinetics of a series of porous Zr metal–organic frameworks with the UiO‐66 topology has been investigated by in situ time‐resolved energy dispersive X‐ray diffraction (EDXRD). Both large aromatic spacers (2,6‐naphthalene‐, 4,4′‐biphenyl‐ and 3,3′‐dichloro‐4,4′‐azobenzene‐dicarboxylates) and a series of X‐functionalized terephthalates (X=NH₂, NO₂, Br, CH₃) were investigated in dimethylformamide (DMF) at different temperatures and compared with the parent UiO‐66. Using different crystallization models, rate constants and further kinetic parameters (such as activation energy) have been extracted. Finally, the impact of the replacement of the toxic DMF by water on the crystallization kinetics was studied through the synthesis of the functionalized UiO‐66‐NO₂ solid.     

Luminescence Tuning and White‐Light Emission of Co‐doped Ln–Cd–Organic Frameworks

Four new three‐dimensional isostructural lanthanide–cadmium metal–organic frameworks (Ln–Cd MOFs), [LnCd₂(imdc)₂(Ac)(H₂O)₂]?H₂O (Ln=Pr ( 1 ), Eu ( 2 ), Gd ( 3 ), and Tb ( 4 ); H₃imdc=4,5‐imidazoledicarboxylic acid; Ac=acetate), have been synthesized under hydrothermal conditions and characterized by IR, elemental analyses, inductively coupled plasma (ICP) analysis, and X‐ray diffraction. Single‐crystal X‐ray diffraction shows that two Ln^III ions are surrounded by four Cd^II ions to form a heteronuclear building block. The blocks are further linked to form 3D Ln–Cd MOFs by the bridging imdc^3? ligand. Furthermore, the left‐ and right‐handed helices array alternatively in the lattice. Eu–Cd and Tb–Cd MOFs can emit characteristic red light with the Eu^III ion and green light with the Tb^III ion, respectively, while both Gd–Cd and Pr–Cd MOFs generate blue emission when they are excited. Different concentrations of Eu³⁺ and Tb³⁺ ions were co‐doped into Gd–Cd/Pr–Cd MOFs, and tunable luminescence from yellow to white was achieved. White‐light emission was obtained successfully by adjusting the excitation wavelength or the co‐doping ratio of the co‐doped Gd–Cd and Pr–Cd MOFs. These results show that the relative emission intensity of white light for Gd–Cd:Eu³⁺,Tb³⁺ MOFs is stronger than that of Pr–Cd:Eu³⁺,Tb³⁺ MOFs, which implies that the Gd complex is a better matrix than the Pr complex to obtain white‐light emission materials.     

A twofold interpenetrating three‐dimensional zinc–organic framework built from naphthalene‐1,4‐dicarboxylate and 4,4′‐bipyridine ligands

A novel three‐dimensional Zn^II complex, poly[[(μ₂‐4,4′‐bipyridine)(μ₄‐naphthalene‐1,4‐dicarboxylato)(μ₂‐naphthalene‐1,4‐dicarboxylato)dizinc(II)] dimethylformamide monosolvate monohydrate], {[Zn₂(C₁₂H₆O₄)₂(C₁₀H₈N₂)]·2C₃H₇NO·H₂O)}_n, has been prepared by the solvothermal assembly of Zn(NO₃)·6H₂O, naphthalene‐1,4‐dicarboxylic acid and 4,4′‐bipyridine. The two crystallographically independent Zn atoms adopt the same four‐coordinated tetrahedral geometry (ZnO₃N) by bonding to three O atoms from three different naphthalene‐1,4‐dicarboxylate (1,4‐ndc) ligands and one N atom from a 4,4′‐bipyridine (bpy) ligand. The supramolecular secondary building unit (SBU) is a distorted paddle‐wheel‐like {Zn₂(COO)₂N₂O₂} unit and these units are linked by 1,4‐ndc ligands within the layer to form a two‐dimensional net parallel to the ab plane, which is further connected by bpy ligands to form the three‐dimensional framework. The single net leaves voids that are filled by mutual interpenetration of an independent equivalent framework in a twofold interpenetrating architecture. The title compound is stable up to 673 K. Excitation and luminescence data observed at room temperature show that it emits bright‐blue fluorescence.     

Defect‐Controlled Preparation of UiO‐66 Metal–Organic Framework Thin Films with Molecular Sieving Capability

Metal–organic framework (MOF) UiO‐66 thin films are solvothermally grown on conducting substrates. The as‐synthesized MOF thin films are subsequently dried by a supercritical process or treated with polydimethylsiloxane (PDMS). The obtained UiO‐66 thin films show excellent molecular sieving capability as confirmed by the electrochemical studies for redox‐active species with different sizes.     

A dihydrogen phosphate anionic network as a host lattice for cations in 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate) and 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1)

In the salt 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate), C₅H₁₃N₂²⁺·2H₂PO₄⁻, (I), and the solvated salt 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1), C₁₀H₉N₂⁺·H₂PO₄⁻·H₃PO₄, (II), the formation of O—H...O and N—H...O hydrogen bonds between the dihydrogen phosphate (H₂PO₄⁻) anions and the cations constructs a three‐ and two‐dimensional anionic–cationic network, respectively. In (I), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional pseudo‐honeycomb‐like supramolecular architecture along the (010) plane. 1‐Methylpiperazine‐1,4‐diium cations are trapped between the (010) anionic layers through three N—H...O hydrogen bonds. In solvated salt (II), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional supramolecular architecture with open channels projecting along the [001] direction. The 2‐(pyridin‐2‐yl)pyridinium cations are trapped between the open channels by N—H...O and C—H...O hydrogen bonds. From a study of previously reported structures, dihydrogen phosphate anions show a supramolecular flexibility depending on the nature of the cations. The dihydrogen phosphate anion may be suitable for the design of the host lattice for host–guest supramolecular systems.     

Post‐Synthetic Ligand Exchange in Zirconium‐Based Metal–Organic Frameworks: Beware of The Defects!

Post‐synthetic ligand exchange in the prototypical zirconium‐based metal–organic framework (MOF) UiO‐66 was investigated by in situ solution ¹H NMR spectroscopy. Samples of UiO‐66 having different degrees of defectivity were exchanged using solutions of several terephthalic acid analogues in a range of conditions. Linker exchange only occurred in defect‐free UiO‐66, whereas monocarboxylates grafted at defect sites were found to be preferentially exchanged with respect to terephthalic acid over the whole range of conditions investigated. A 1:1 exchange ratio between the terephthalic acid analogue and modulator was observed, providing evidence that the defects had missing‐cluster nature. Ex situ characterisation of the MOF powders after exchange corroborated these findings and showed that the physical‐chemical properties of the MOF depend on whether the functionalisation occurs at defective sites or on the framework.     

Hydrothermal Synthesis,Structure, and Optical Properties of Two Nanosized Ln26@CO3 (Ln=Dy and Tb) Cluster‐Based Lanthanide–Transition‐Metal–Organic Frameworks (Ln MOFs)

Two Ln₂₆@CO₃ (Ln=Dy and Tb) cluster‐based lanthanide–transition‐metal–organic frameworks (Ln MOFs) formulated as [Dy₂₆Cu₃(Nic)₂₄(CH₃COO)₈(CO₃)₁₁(OH)₂₆(H₂O)₁₄]Cl ? 3 H₂O ( 1 ; HNic=nicotinic acid) and [Tb₂₆NaAg₃(Nic)₂₇(CH₃COO)₆(CO₃)₁₁(OH)₂₆Cl(H₂O)₁₅] ? 7.5 H₂O ( 2 ) have been successfully synthesized by hydrothermal methods and characterized by IR, thermogravimetric analysis (TGA), elemental analysis, and single X‐ray diffraction. Compound 1 crystallizes in the monoclinic space group Cc with a=35.775(12) Å, b=33.346(11) Å, c=24.424(8) Å, β=93.993(5)°, V=29065(16) ų, whereas 2 crystallizes in the triclinic space group P with a=20.4929(19) Å, b=24.671(2) Å, c=29.727(3) Å, α=81.9990(10)°, β=88.0830(10)°, γ=89.9940(10)°, V=14875(2) ų. Structural analysis indicates the framework of 1 is a 3D perovskite‐like structure constructed out of CO₃@Dy₂₆ building units and Cu⁺ centers by means of nicotinic acid ligand bridging. In 2 , however, nanosized CO₃@Tb₂₆ units and [Ag₃Cl]²⁺ centers are connected by Nic^? bridges to give rise to a 2D structure. It is worth mentioning that this kind of 4d–4f cluster‐based MOF is quite rare as most of the reported analogous compounds are 3d–4f ones. Additionally, the solid‐state emission spectra of pure compound 2 at room temperature suggest an efficient energy transfer from the ligand Nic^? to Tb³⁺ ions, which we called the “antenna effect”. Compound 2 shows a good two‐photon absorption (TPA) with a TPA coefficient of 0.06947 cm GM^?1 (1 GM=10^?50 cm⁴ s photon^?1), which indicates that compound 2 might be a good choice for third‐order nonlinear optical materials.     

Chiral Reticular Self‐Assembly of Achiral AIEgen into Optically Pure Metal–Organic Frameworks (MOFs) with Dual Mechano‐Switchable Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) is attractive in understanding the excited‐state chirality and developing advanced materials. Herein, we propose a chiral reticular self‐assembly strategy to unite achiral AIEgens, chirality donors, and metal ions to fabricate optically pure AIEgen metal–organic frameworks (MOFs) as efficient CPL materials. We have found that CPL activity of the single‐crystal AIEgen MOF was generated by the framework‐enabled strong emission from AIEgens and through‐space chirality transfer from chirality donors to achiral AIEgens via metal‐ion bridges. For the first time, a dual mechano‐switched blue and red‐shifted CPL activity was achieved via ultrasonication and grinding, which enabled the rotation or stacking change of AIEgen rotors with the intact homochiral framework. This work provided not only an insightful view of the aggregation induced emission (AIE) mechanism, but also an efficient and versatile strategy for the preparation of stimuli‐responsive CPL materials.     

Cooperative Cluster Metalation and Ligand Migration in Zirconium Metal–Organic Frameworks

Cooperative cluster metalation and ligand migration were performed on a Zr‐MOF, leading to the isolation of unique bimetallic MOFs based on decanuclear Zr₆M₄ (M=Ni, Co) clusters. The M²⁺ reacts with the μ₃‐OH and terminal H₂O ligands on an 8‐connected [Zr₆O₄(OH)₈(H₂O)₄] cluster to form a bimetallic [Zr₆M₄O₈(OH)₈(H₂O)₈] cluster. Along with the metalation of Zr₆ cluster, ligand migration is observed in which a Zr–carboxylate bond dissociates to form a M–carboxylate bond. Single‐crystal to single‐crystal transformation is realized so that snapshots for cooperative cluster metalation and ligand migration processes are captured by successive single‐crystal X‐ray structures. In³⁺ was metalated into the same Zr‐MOF which showed excellent catalytic activity in the acetaldehyde cyclotrimerization reaction. This work not only provides a powerful tool to functionalize Zr‐MOFs with other metals, but also structurally elucidates the formation mechanism of the resulting heterometallic MOFs.