Search

Metal–organic frameworks (MOFs) based on high-connected nets are generally very attractive due to their combined robustness and porosity. Here, we describe the synthesis of BCN-348, a new high-connected Zr-MOF built from an 8-connected (8-c) cubic Zr-oxocluster and an 8-c organic linker. BCN-348 contains a minimal edge-transitive 3,4,8-c eps net, and combines mesoporosity with thermal and hydrolytic stability. Encouraging results from preliminary studies on its use as a catalyst for hydrolysis of a nerve-agent simulant suggest its potential as an agent for detoxification of chemical weapons and other pernicious compounds. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) possess high CO2 adsorption properties and are considered to be a promising candidate for the electrochemical carbon dioxide reduction reaction (eCO2RR). However, their insufficient selectivity and current density constrain their further exploration in the eCO2RR. In this work, by introducing a very small proportion of 2,5-dihydroxyterephthalic acid (DOBDC) into ZIF-8, a surface modified ZIF-8-5% catalyst was synthesized by a post-modification method, exhibiting enhanced selectivity (from 56% to 79%) and current density (from −4 mA cm−2 to −10 mA m−2) compared to ZIF-8. Density functional theory (DFT) calculations further demonstrate that the boosted eCO2RR performance on ZIF-8-5% could be attributed to the improved formation of the *COOH intermediate stemming from successful DOBDC surface modification. This work opens a new path for improving the catalytic properties of MOFs via their surface modification. [ABSTRACT FROM AUTHOR]

Self-assembly of colloidal particles into ordered superstructures enables the development of novel advanced materials for diverse applications such as photonics, electronics, sensing, energy conversion, energy storage, diagnosis, drug or gene delivery, and catalysis. Recently, polyhedral metal–organic framework (MOF) particles have been proposed as promising colloidal particles to form ordered superstructures, based on their colloidal stability, size-tunability, rich polyhedral shapes, porosity and multifunctionality. In this review, we present a comprehensive overview of strategies for the self-assembly of colloidal MOF particles into ordered superstructures of different dimensionalities, highlighting some of their properties and applications, and sharing thoughts on the self-assembly of MOF particles. [ABSTRACT FROM AUTHOR]

Increasing the chemical complexity of metal–organic cages (MOCs) or polyhedra (MOPs) demands control over the simultaneous organization of diverse organic linkers and metal ions into discrete caged structures. Herein, we show that a pre-assembled complex of the archetypical cuboctahedral MOP can be used as a template to replicate such caged structure, one having a "triblock Janus-type" configuration that is both heterometallic and heteroleptic. [ABSTRACT FROM AUTHOR]

We have synthesised and characterised the two possible isomers of heteroleptic trigonal antiprismatic M12L6L′6 MOPs by screening reactions of rhodium acetate with different pairs of complementary dicarboxylate linkers. The resulting 12 new MOPs (eight of isomer A + four of isomer B) are microporous in the solid state, exhibiting Brunauer–Emmett–Teller (BET) surface areas as high as 770 m2 g−1. [ABSTRACT FROM AUTHOR]

Herein we report the design, synthesis, structural characterisation and functional testing of a series of Cu(II) coordination polymers containing flexible 4,4′-dithiodibenzoate ligand (4,4′-DTBA), with or without auxiliary N-donor ligands. Reaction of Cu(II) with 4,4′-DTBA yielded a 1D coordination polymer (1) based on Cu(II) paddlewheel units connected by 4,4′-DTBA, to form cyclic loop chains with intramolecular voids that exhibit reversible structural transformations upon subsequent solvent exchange in methanol to afford a new, crystalline, permanently-porous structure (1′). However, when the same reaction was run with pyridine, it formed a porous 2D coordination polymer (2). We have attributed the difference in dimensionality seen in the two products to the coordination of pyridine on the axial site of the Cu(II) paddle-wheel, which forces flexible 4,4′-DTBA to adopt a different conformation. Reactions in the presence of 4,4′-bipyridine (4,4′-bpy) afforded two new, flexible, 2D coordination polymers (3 & 4). Lower concentrations of 4,4′-bpy afforded a structure (3) built from 1D chains analogous to those in 1 and connected through 4,4′-bpy linkers coordinated to the axial positions. Interestingly, 3 showed reversible structural transformations triggered by either solvent exchange or thermal treatment, each of which yielded a new crystalline and permanently porous phase (3′). Finally, use of higher concentrations of 4,4′-bpy led to a coordination polymer (4) based on a distorted CuO3N2 trigonal bipyramid, rather than on the Cu(II) paddlewheel. The connection of these motifs by 4,4′-DTBA resulted in a zig-zag 1D chain connected through 4,4′-bpy ligands to form a porous 2D network. Interestingly, 4 also underwent reversible thermal transformation to yield a microporous coordination polymer (4′). [ABSTRACT FROM AUTHOR]

Dynamic covalent bonds have been advantageously used to direct the synthesis of crystalline porous covalent organic frameworks (COFs). Unlike the standard synthetic protocols that involve harsh conditions, this work provides a high-yield "one-pot" green synthesis of imine-based COFs in water. Additionally, this aqueous synthesis can be performed under microwave conditions, considerably reducing the reaction time. [ABSTRACT FROM AUTHOR]

The production of metal–organic frameworks (MOFs) in the form of colloids has brought a paradigm shift in the design of new functional porous materials. Along with their intrinsic interest as porous solids, and contrary to their bulk powder counterparts, colloidal MOF particles can additionally be dispersed, shaped, functionalized, transformed and assembled in a controlled manner, conferring them further properties and applications. In this regard, zeolitic imidazolate framework-8 (ZIF-8) has become a pioneering MOF constituent of colloidal science. Today, the understanding of the role of synthetic parameters, learned after one decade of research, enables the production of monodisperse colloidal ZIF-8 particles with tunable dimensions and morphologies, offering the opportunity to develop new functional materials and composites with novel and promising functionalities. This tutorial review provides a useful guide to prepare ZIF-8 in its colloidal form, covering the published studies on the synthesis of homogeneous ZIF-8 particles with controlled size and shape. In addition, we present the most relevant advances in the development of colloidal ZIF-8 hybrid single-particles, reflecting the great potential and rapid development of this interdisciplinary research field. Finally, we highlight how formulation of ZIF-8 as colloids has led to the emergence of novel physicochemical phenomena that are useful for practical applications. This review aims at promoting the development of MOFs as colloids, taking ZIF-8 as a pioneering and successful case that clearly shows the benefits of bridging MOF chemistry and colloidal science. [ABSTRACT FROM AUTHOR]

Supramolecular isomerism of metal–organic frameworks (MOFs) is known for several MOF structures, having direct implications on the properties of these materials. Although the synthesis of MOF isomers is mainly serendipitous in nature, achieving controlled formation of a target framework is highly relevant for practical applications. This work discusses the influence of additives and synthesis conditions on the formation of porous isomers containing Zn2+ as nodes and 2,5-dihydroxy-1,4-benzenedicarboxylate (dobdc4–) as a linker. Using solvent mixtures containing strongly coordinated molecules, e.g. N,N′-dimethylformamide (DMF) and N-methylpyrrolidone (NMP), facilitates the formation of porous structures of type [Zn2(dobdc)(S)x]·yS (S = DMF, NMP) which are built from dinuclear Zn2(O)2(CO2)3 secondary building units (SBUs) consisting of two different edge-sharing polyhedra with the Zn2+ ions in a unsaturated coordinative environment. In the presence of water, the Zn2+ dimers are converted to one-dimensional infinite Zn2+ chains, in which the number of Zn2+-linker bonds increases, therefore giving a hydrolytically more stable coordination environment. The full characterization of the isomers as well as their conversion to the most stable isomer is presented. [ABSTRACT FROM AUTHOR]

A novel naphthalene-based 5·(BArF)8 capsule allows for the size-selective inclusion of C60 from fullerene mixtures. Its size selectivity towards C60 has been rationalized by its dynamic adaptability in solution that has been investigated by molecular dynamics. Additionally, 5·(BArF)8 encapsulates C60-derivatives such as C60-PCBM and N-methylpyrrolidine-C60. The latter can be separated from C60 since 5·(BArF)8 displays distinct affinity for them. [ABSTRACT FROM AUTHOR]

Here, we report the covalent post-synthetic modification (CPSM) of MOFs using the photothermal effect. Specifically, we subjected mixtures of a photothermally active MOF and another reagent to irradiation with a UV-Vis lamp. This caused the MOF to heat up, which in turn caused the other reagent to melt and subsequently react with the functional groups on the walls of the MOF pores. We have exploited this dual function of MOFs as both heater and host for CPSMs to achieve rapid formation of amides from the reaction of representative MOFs (UiO-66-NH2 or MIL-101-NH2-(Al)) with anhydrides under solvent-free conditions. In addition, this approach enables more complex CPSMs in MOFs such as the formation of amides in UiO-66-NH2 by using an aldehyde through a cascade reaction. [ABSTRACT FROM AUTHOR]

Porous metal–organic frameworks (MOFs) are attracting great attention from industry, thanks to their myriad potential applications in areas such as catalysis and gas storage. Zr-MOFs (also known as UiO-type MOFs) are especially promising, owing to their large surface areas, high chemical versatility and remarkable hydrothermal, chemical and thermal stabilities. However, among the challenges currently precluding the industrial exploitation of MOFs is the lack of green methods for their synthesis. Herein we describe a continuous-flow spray-drying method for the simultaneous synthesis and shaping of spherical MOF microbeads in a mixture of water and acetic acid. We used this approach to build two archetypical Zr-MOFs: UiO-66-NH2 and Zr-fumarate. By tuning the concentration of acetic acid in water, we were able to produce, by a scalable process, UiO-66-NH2 and Zr-fumarate beads with SBET and water-sorption values comparable to the literature values obtained with other methods. [ABSTRACT FROM AUTHOR]

Here we report a method that combines the spray-drying technique with a dynamic covalent chemistry process to synthesize zero-dimensional, spherical and microscale superstructures made from the assembly of imine-based COF nanocrystals. This methodology also enables the integration of other functional materials into these superstructures forming COF-based composites. [ABSTRACT FROM AUTHOR]

Here, we show that the well-known hydrophobic leucine (Leu) zipper motif (also known as the coiled-coil or Leu scissors motif), typically found in proteins, can be used as a source of inspiration in coordination polymers built from Leu-containing dipeptides or tripeptides. We demonstrate that this motif can be extended to form Velcro-like layers of Leu, and that the hydrophobicity of these layers is transferred to coordination polymers, thereby enabling the development of a new type of hydrophobic materials. [ABSTRACT FROM AUTHOR]

The potential commercial applications for metal organic frameworks (MOFs) are tantalizing. To address the opportunity, many novel approaches for their synthesis have been developed recently. These strategies present a critical step towards harnessing the myriad of potential applications of MOFs by enabling larger scale production and hence real-world applications. This review provides an up-to-date survey ( references) of the most promising novel synthetic routes, i.e., electrochemical, microwave, mechanochemical, spray drying and flow chemistry synthesis. Additionally, the essential topic of downstream processes, especially for large scale synthesis, is critically reviewed. Lastly we present the current state of MOF commercialization with direct feedback from commercial players. [ABSTRACT FROM AUTHOR]

Herein we report a water-induced single-crystal to single-crystal transformation that involves the formation of hetero-bimetallic paddlewheel clusters in coordination polymers. Through this transformation, which involves the cleavage and formation of different coordination bonds, two different Cu(ii)–Zn(ii) and Cu(ii)–Ni(ii) paddlewheel units exhibiting a 1 : 1 metal ratio were created. [ABSTRACT FROM AUTHOR]

Herein we report a study on water adsorption/desorption-triggered single-crystal to single-crystal transformations in a MOF, by single-crystal and humidity-controlled powder X-ray diffraction and water-sorption measurements. We identified a gate-opening effect at a relative humidity of 85% upon water adsorption, and a gate-closure effect at a relative humidity of 55 to 77% upon water desorption. This reversible breathing effect between the “open” and the “closed” structures of the MOF involves the cleavage and formation of several coordination bonds. [ABSTRACT FROM AUTHOR]

Herein we report a versatile methodology for engineering metallic Janus MOF particles based on desymmetrization at interfaces, whereby each MOF particle is partially coated with a desired metal. We demonstrate that it enables the fabrication of homogeneous Janus MOF particles according to the MOF (ZIF-8, UiO-66 or UiO-66-SH), the metal (Au, Co or Pt), the MOF particle size (from the micrometer to the submicrometer regime) and the metal-film thickness (from 5 nm to 50 nm) employed. We anticipate that our strategy could be applied to impart new functionalities to MOFs, including asymmetric functionalization, magnetic-guidance and motorization. [ABSTRACT FROM AUTHOR]

We have prepared three distinct polyamino acid-based metal--organic frameworks (MOFs) with different chiralities and porosities using the same chemistry, by simply modifying the enantiomeric ratio of the chiral organic ligand used. [ABSTRACT FROM AUTHOR]

Supramolecular assemblages between three different [Zr(A)4]4− metallotectons (A stands for oxalate, Ox2−; dihydrobenzoquinonate, DBQ2−; or chloranilate CA2−) and three different guanidinium cation analogues (guanidinium, H-Guan+; 2-amino-imidazolium, H-AIm+; and N,N-dimethylguanidinium, H-DmG+) have been envisioned to investigate how the anionic and/or cationic building-block characteristics influence the connectivity and/or the dimensionality of frameworks based on charge-assisted H-bonds. Added to the benchmark material, {(H-Guan)4[Zr(Ox)4]}, (1), the crystal structures of six architectures of formula {(H-AIm)4[Zr(Ox)4]}·5H2O (2), {(H-DmG)4[Zr(Ox)4]}·0.5H2O (3), {(H-Guan)4[Zr(DBQ)4]}·1.5H2O (4), {(H-Guan)4[Zr(CA)4]}·5.85H2O (5), {(H-AIm)4[Zr(CA)4]}·H2O (6), and {K2(H2O)3(H-DmG)2[Zr(DBQ)4]}·H2O (7) have been characterized. While 1 consists of a two dimensional (2D) H-bonded network with compact structure, four out of the six supramolecular architectures (2–7) form 3D H-bonded networks, and three of these materials (namely, 2, 4 and 5) present open-framework architectures with solvent accessible voids ranging from 8 to 13%. Compounds 4–7 are the first examples of H-bonded frameworks constructed from [Zr(DBQ)4]4− and [Zr(CA)4]4− metallotectons. [ABSTRACT FROM AUTHOR]

Micro- and nanoscale coordination polymer particles can be used for encapsulating and delivering drugs. In vitrocancer cell cytotoxicity assays showed that these capsules readily release doxorubicin, which shows anticancer efficacy. The results from this work open up new avenues for metal–organic capsules to be used as potential drug delivery systems. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) possess high CO 2 adsorption properties and are considered to be a promising candidate for the electrochemical carbon dioxide reduction reaction (eCO 2 RR). However, their insufficient selectivity and current density constrain their further exploration in the eCO 2 RR. In this work, by introducing a very small proportion of 2,5-dihydroxyterephthalic acid (DOBDC) into ZIF-8, a surface modified ZIF-8-5% catalyst was synthesized by a post-modification method, exhibiting enhanced selectivity (from 56% to 79%) and current density (from -4 mA cm -2 to -10 mA m -2 ) compared to ZIF-8. Density functional theory (DFT) calculations further demonstrate that the boosted eCO 2 RR performance on ZIF-8-5% could be attributed to the improved formation of the *COOH intermediate stemming from successful DOBDC surface modification. This work opens a new path for improving the catalytic properties of MOFs via their surface modification.

We have synthesised and characterised the two possible isomers of heteroleptic trigonal antiprismatic M 12 L 6 L' 6 MOPs by screening reactions of rhodium acetate with different pairs of complementary dicarboxylate linkers. The resulting 12 new MOPs (eight of isomer A + four of isomer B) are microporous in the solid state, exhibiting Brunauer-Emmett-Teller (BET) surface areas as high as 770 m 2 g -1 .

Herein we report the design, synthesis, structural characterisation and functional testing of a series of Cu(ii) coordination polymers containing flexible 4,4'-dithiodibenzoate ligand (4,4'-DTBA), with or without auxiliary N-donor ligands. Reaction of Cu(ii) with 4,4'-DTBA yielded a 1D coordination polymer (1) based on Cu(ii) paddlewheel units connected by 4,4'-DTBA, to form cyclic loop chains with intramolecular voids that exhibit reversible structural transformations upon subsequent solvent exchange in methanol to afford a new, crystalline, permanently-porous structure (1'). However, when the same reaction was run with pyridine, it formed a porous 2D coordination polymer (2). We have attributed the difference in dimensionality seen in the two products to the coordination of pyridine on the axial site of the Cu(ii) paddle-wheel, which forces flexible 4,4'-DTBA to adopt a different conformation. Reactions in the presence of 4,4'-bipyridine (4,4'-bpy) afforded two new, flexible, 2D coordination polymers (3 & 4). Lower concentrations of 4,4'-bpy afforded a structure (3) built from 1D chains analogous to those in 1 and connected through 4,4'-bpy linkers coordinated to the axial positions. Interestingly, 3 showed reversible structural transformations triggered by either solvent exchange or thermal treatment, each of which yielded a new crystalline and permanently porous phase (3'). Finally, use of higher concentrations of 4,4'-bpy led to a coordination polymer (4) based on a distorted CuO 3 N 2 trigonal bipyramid, rather than on the Cu(ii) paddlewheel. The connection of these motifs by 4,4'-DTBA resulted in a zig-zag 1D chain connected through 4,4'-bpy ligands to form a porous 2D network. Interestingly, 4 also underwent reversible thermal transformation to yield a microporous coordination polymer (4').

A novel naphthalene-based 5·(BArF)8 capsule allows for the size-selective inclusion of C60 from fullerene mixtures. Its size selectivity towards C60 has been rationalized by its dynamic adaptability in solution that has been investigated by molecular dynamics. Additionally, 5·(BArF)8 encapsulates C60-derivatives such as C60-PCBM and N-methylpyrrolidine-C60. The latter can be separated from C60 since 5·(BArF)8 displays distinct affinity for them.

Here, we show that the well-known hydrophobic leucine (Leu) zipper motif (also known as the coiled-coil or Leu scissors motif), typically found in proteins, can be used as a source of inspiration in coordination polymers built from Leu-containing dipeptides or tripeptides. We demonstrate that this motif can be extended to form Velcro-like layers of Leu, and that the hydrophobicity of these layers is transferred to coordination polymers, thereby enabling the development of a new type of hydrophobic materials.

Biomolecules are the building blocks of life. Nature has evolved countless biomolecules that show promise for bridging metal ions. These molecules have emerged as an excellent source of biocompatible building blocks that can be used to design Metal-Biomolecule Frameworks (MBioFs). This feature article highlights the advances in the synthesis of this class of MOFs. Special emphasis is provided on the crystal structures of these materials, their miniaturization to the submicron length scale, and their new potential storage, catalytic, and biomedical applications.

Progress in microelectronics, sensors and optics is strongly dependent on the miniaturization of components, and the integration of nanoscale structures into applicable systems. In this regard, conventional top-down technologies such as lithography have limits concerning the dimensions and the choice of material. Therefore, several bottom-up approaches have been investigated to satisfy the need for structures with large aspect ratios in the nanometre regime. For further implementation, however, it is crucial to find methods to define position, orientation and length of the nanowires. In this study, we present a microchip to trap in situ formed bundles of nanowires in microsized cages and clamps, thereby enabling immobilisation, positioning and cutting-out of desired lengths. The microchip consists of two layers, one of which enables the formation of metal-organic nanowires at the interface of two co-flowing laminar streams. The other layer, separated by a thin and deflectable PDMS membrane, serves as the pneumatic control layer to impress microsized features ("donuts") onto the nanowires. In this way, a piece of the nanowire bundle with a prescribed length is immobilised inside the donut. Furthermore, partly open ring-shaped structures enabled trapping of hybrid wires and subsequent functionalisation with fluorescent beads. We believe that the method is a versatile approach to form and modify nanoscale structures via microscale tools, thereby enabling the construction of fully functional nanowire-based systems.

The reaction of a 3-connecting PTMTC radical with Tb(III) ions forms a three-dimensional open-framework with the formula [Tb(PTMTC)(DMF)(3)] (1), which associates a lattice complex T topology with large channels, guest-induced reversible crystal to amorphous transformations and ferromagnetic metal-radical interactions.

3D coordination cages have been synthesized via the supramolecular 3 + 2 self-assembly of macrocyclic dicopper molecular clips and tricarboxylate linkers, the nature of which allows the introduction of different functionalities to the 3D cages.

Metal-organic sub-50 nm spherical particles that exhibit single-molecule magnet behaviour have been fabricated by direct precipitation of Mn(12)O(12) clusters in a mixture of acetonitrile and toluene.

Two novel Mn12 derivatives [Mn12O12(O2CC[triple bond]CH)16(H2O)4] x 3H2O (1) and [Mn12(O2CC[triple bond]CC6H5)16(H2O)4] x 3H2O (2) have been prepared and characterized. Magnetic measurements confirm that both function as single-molecule magnets (SMM), showing frequency-dependent out-of-phase AC susceptibility signals and magnetization hysteresis curves. Thermal stability studies of both complexes were first conducted in the solid state. While complex 1 undergoes a sudden exothermal decomposition at T(onset) = 118 degrees C, complex 2 exhibits a higher stability. Thermolysis reaction of 1 was hence assessed in solution to yield dark red crystals of a two-dimensional Mn(II)-based co-ordination polymer [Mn3(O2CC[triple bond]CH)6(H2O)4] x 2H2O (3), which corresponds to an extended sheet-like structure that crystallizes in the monoclinic space group P2(1)/n; a = 9.2800(2) angstroms, b = 9.4132(2) angstroms, c = 14.9675(3) angstroms, beta = 99.630(1) degrees, and Z = 2. Finally, the magnetic properties of complex 3 have been studied on an oriented single crystal over two different orientations of the reciprocal vector versus the external field.

The utilization of tetrahedral pre-formed coordination compounds {M(C2O4)4}4- (M = Zr(IV), U(IV); C2O4(2-) = oxalate) permitted the efficient construction of rare examples of heteronuclear supramolecular nano-porous architectures. A series of metal-organic coordination frameworks prepared by association of these building units with either Mn2+, Cd2+, or Mg2+ have been structurally characterized and are described. Their 3-D chemical scaffold is based on the primary tetrahedral building unit but their pore sizes and topologies could be varied through the M2+ metal ion involved in the assembling process, and the anionic tetrahedral moiety. These structures display channels with apertures up to 12 Angstrom x 8 Angstrom which are emptied of solvates at mild temperatures without affecting the chemical scaffold, the integrity of which is maintained up to 250-300 degrees C. A certain degree of flexibility of the coordination polymers upon guest release is suggested by the temperature dependence of the powder X-ray patterns and N2 sorption experiments, but reversible and selective sorption of small molecules has been observed substantiating that these open-frameworks behave like sponges.

The utilization of the tetrahedral pre-formed coordination compound {U(C(2)O(4))(4)}(4-) permitted the efficient synthesis of a 3D heteronuclear supramolecular nano-porous architecture undergoing a reversible sorption process without collapsing.