Adsorptive-dissolution of O into the potential nanospace of a densely fluorinated metal-organic framework.

Nanoporous solids, including metal-organic frameworks (MOFs), have long been known to capture small molecules by adsorption on their pore surfaces. Liquids are also known to accommodate small molecules by dissolution. These two processes have been recognized as fundamentally distinct phenomena because of the different nature of the medium-solids and liquids.

Development of a Ru-porphyrin-based supramolecular framework catalyst for styrene epoxidation.

A new microporous supramolecular-framework Ru(II)-porphyrin catalyst containing non-covalent interactions between pyrenylphenyl moieties at the -position of the porphyrin ring is synthesised and structurally characterised. This recyclable catalyst expedites styrene epoxidation more efficiently than homogeneous Ru-porphyrin catalytic systems.

Selective electrochemical CO conversion with a hybrid polyoxometalate.

A multi-component coordination compound, in which ruthenium antenna complexes are connected to a polyoxotungstate core is presented. This hybrid cluster effectively promotes the electrochemical conversion of CO to C1 feedstocks, the selectivity of which can be controlled by the acidity of the media.

Beyond the Conventional Limitation of Photocycloaddition Reaction in the Roomy Nanospace of a Metal-Organic Framework.

Topochemical reactions provide selective products based on the molecular position; however, they generally require molecules to be placed in strictly limited orientations and distances, making them less versatile. In this study, we found that by confining -4-styrylpyridine (4-spy) as a reactive substrate in a flexible metal-organic framework (MOF) nanospace, [2+2] cycloadducts can be selectively obtained, even when the distance between two C═C bonds of 4-spy in the crystal is 5.9 Å, which is much larger than the conventionally observed upper limit (4.

Covalent organic framework atropisomers with multiple gas-triggered structural flexibilities.

Covalent organic frameworks (COFs) are emerging crystalline porous polymers, showing great potential for applications but lacking gas-triggered flexibility. Atropisomerism was experimentally discovered in 1922 but has rarely been found in crystals with infinite framework structures. Here we report atropisomerism in COF single crystals.

Creation of single molecular conjugates of metal-organic cages and DNA.

Here we report the development of an equimolar conjugate of a metal-organic cage (MOC) and DNA (MOC-DNA). Several MOC-DNA conjugates were assembled into a programmed structure by coordinating with a template DNA having a complementary base sequence. Moreover, conjugation with the MOC drastically enhanced the permeability of DNA through the lipid bilayer, presenting great potential as a drug delivery system.

Design of a MOF based on octa-nuclear zinc clusters realizing both thermal stability and structural flexibility.

An octa-nuclear zinc (Zn) cluster-based two-fold interpenetrated metal-organic framework (MOF) of [(CH)NH][ZnO(FDC)]·7DMF (denoted as Zn8-as; HFDC = 9-fluorene-2,7-dicarboxylic acid; DMF = ,-dimethylformamide) was synthesized by the reaction of a hard base of a curved dicarboxylate ligand (HFDC) with the borderline acid of Zn(II) under solvothermal conditions. Zn8-as shows significant crystal volume shrinkage upon heating, yielding a solvate-free framework of [(CH)NH][ZnO(FDC)] (Zn8-de). Zn8-de displays gated adsorption for CH and type-I adsorption for CO, attributed to the framework flexibility and the different interactions between the gas molecules and the host framework.

Stabilization of radical active species in a MOF nanospace to exploit unique reaction pathways.

We synthesized a metal-organic framework (MOF) using a ligand bearing haloalkoxy chains as a radical precursor. The radicals generated in the MOF upon photoirradiation were stable even at 250 K or under an O atmosphere, despite radicals generated from the ligand decomposing at 200 K; thus, the regular arrangement of radicals effectively stabilized them. Moreover, a unique photoproduct was obtained only in the MOF, indicating that the confinement effect in the nanospace enabled a specific reaction that did not occur in the bulk state.

Fabrication of a Kagomé-type MOF Membrane by Seeded Growth on Amino-functionalized Porous Al O Substrate.

In this study, we report an efficient fabrication method for the membrane of a metal-organic framework (MOF) (Kgm-OEt) which is one kind of kagomé-type MOF with a two-dimensional (2D) sheet structure having one-dimensional (1D) channels suitable for separation of H from other larger gases. The Kgm-OEt seed layer was created on an Al O substrate using layer-by-layer (LBL) growth, then a membrane was fabricated by secondary growth. The membrane on a 3-aminopropyltriethoxysilane (APTEs)-treated substrate obtained in this method was continuous and defect-free with the crystal orientation suitable for gas transportation, while the membrane grown on an unmodified substrate was loosely packed with unfavorable crystal orientation.

Triplet Carbene with Highly Enhanced Thermal Stability in the Nanospace of a Metal-Organic Framework.

Triplet carbenes (s) are of great interest due to their magnetic properties and reactivity, which descend from s' unique electronic state. However, the reactivity and stability of s are usually a trade-off, and it is difficult to achieve both at the same time. In this work, we were able to enhance the thermal stability of a species while maintaining its reactivity by confining them in the nanospace of a metal-organic framework (MOF).

An Open-shell, Luminescent, Two-Dimensional Coordination Polymer with a Honeycomb Lattice and Triangular Organic Radical.

The use of organic radicals as building blocks is an effective approach to the production of open-shell coordination polymers (CPs). Two-dimensional (2D) CPs with honeycomb spin-lattices have attracted attention because of the unique electronic structures and physical properties afforded by their structural topology. However, radical-based CPs with honeycomb spin-lattices tend to have low chemical stability or poor crystallinity, and thus novel systems with high crystallinity and persistence are in strong demand.

Trapping and Releasing of Oxygen in Liquid by Metal-Organic Framework with Light and Heat.

Nanoporous materials can adsorb small molecules into their nanospaces. However, the trapping of light gas molecules dissolved in solvents suffers from low concentration and poor adsorption affinity. Here, the reversible trapping and releasing of dissolved oxygen are shown through integrating photosensitization and chemical capturing abilities into a metal-organic framework (MOF), MOMF-1.

Molecular motion in the nanospace of MOFs upon gas adsorption investigated by in situ Raman spectroscopy.

Molecular motions taking place in the nanospace of metal-organic frameworks (MOFs) are an interesting research subject, although not yet fully investigated. In this work, we utilized in situ Raman spectroscopy in the ultralow-frequency region to investigate the libration motion (including the rotational motion of phenylene rings) of MOFs, in particular [Cu(bdc)(dabco)] (Cu-JAST-1), where bdc = 1,4-benzenedicarboxylate and dabco = 1,4-diazabicyclo[2.2.

Hysteresis in the gas sorption isotherms of metal-organic cages accompanied by subtle changes in molecular packing.

Structural deformation in response to gas sorption is rarely observed for porous molecular solids, when compared to porous framework materials. Here, we describe the effect of chemical modification on the exterior of lantern-type metal-organic cages on the emergence and then disappearance of cooperative gas uptake. The results suggest that supramolecular design of ligands can be used to reveal this behaviour.

Direct observation of dimethyl sulfide trapped by MOF proving efficient removal of sulfur impurities.

Here, we report the adsorptive removal of trace amounts of dimethyl sulfide (DMS) using metal-organic frameworks (MOFs). Cu-based MOFs with open metal sites (OMSs), [Cu(btc)] (HKUST-1), where btc = 1,3,5-benzenetricarboxylate, and without OMSs, [Cu(bdc)(dabco)] (Cu-JAST-1), where bdc = 1,4-benzenedicarboxylate and dabco = 1,4-diazabicyclo[2.2.

Dynamic Topochemical Reaction Tuned by Guest Molecules in the Nanospace of a Metal-Organic Framework.

Reaction in well-designed solids allows yielding products with high selectivity and unique compounds that cannot be obtained in solution. However, the precise tuning of the arrangement of reactants in solids for the versatile application of solid-phase reactions remains a challenging subject. Here, a [2 + 2] photocyclization reaction at different positions of the carbon-carbon bonds is described in which the spatial arrangement of 4-styrylpyridines (4-spy) is changed by guest molecules in a flexible metal-organic framework.

Reversible low-temperature redox activity and selective oxidation catalysis derived from the concerted activation of multiple metal species on Cr and Rh-incorporated ceria catalysts.

The ceria-based catalyst incorporated with Cr and a trace amount of Rh (CrRhCeO) was prepared and the reversible redox performances and oxidation catalysis of CO and alcohol derivatives with O at low temperatures (<373 K) were investigated. In situ X-ray absorption fine structure (XAFS), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM)-EDS/EELS and temperature-programmed reduction/oxidation (TPR/TPO) revealed the structures and redox mechanisms of three metals in CrRhCeO: dispersed Rh species (<1 nm) and CrO nanoparticles (∼1 nm) supported on CeO in CrRhCeO were transformed to Rh nanoclusters, Cr(OH) species and CeO with two Ce-oxide layers at the surface in a concerted activation manner of the three metal species with H.

One-Step Synthesis of an Adaptive Nanographene MOF: Adsorbed Gas-Dependent Geometrical Diversity.

A layered metal-organic framework (MOF) comprising extra-large nanographene sheets, , was successfully synthesized using a dicarboxylic acid derivative of hexa--hexabenzocoronene (LH), and its structure was characterized by single-crystal X-ray diffraction analysis. The crystal structure shows that 2D layers composed of a dinuclear Zn complex unit and L are located on top of each other through multiple weak interlayer bonds, affording , having three dimensionally connected nanopores with large nanographene surfaces. The HBC-based nanographene sheets are anchored to the MOF framework via two zinc carboxylate linkages and therefore have an axial rotational freedom.

Microwave-Assisted Hydrothermal Synthesis of [Al(OH)(1,4-NDC)] Membranes with Superior Separation Performances.

In this study, we report a facile ligand-assisted in situ hydrothermal approach for preparation of compact [Al(OH)(1,4-NDC)] (1,4-NDC=1,4-naphthalenedicarboxylate) MOF membranes on porous γ-Al O substrates, which also served as the Al source of MOF membranes. Simultaneously, it was observed that the heating mode exerted significant influence on the final microstructure and separation performance of [Al(OH)(1,4-NDC)] membranes. Compared with the conventional hydrothermal method, the employment of microwave heating led to the formation of [Al(OH)(1,4-NDC)] membranes composed of closely packed nanorods with superior H /CH selectivity.

Design and control of gas diffusion process in a nanoporous soft crystal.

Design of the gas-diffusion process in a porous material is challenging because a contracted pore aperture is a prerequisite, whereas the channel traffic of guest molecules is regulated by the flexible and dynamic motions of nanochannels. Here, we present the rational design of a diffusion-regulatory system in a porous coordination polymer (PCP) in which flip-flop molecular motions within the framework structure provide kinetic gate functions that enable efficient gas separation and storage. The PCP shows substantial temperature-responsive adsorption in which the adsorbate molecules are differentiated by each gate-admission temperature, facilitating kinetics-based gas separations of oxygen/argon and ethylene/ethane with high selectivities of ~350 and ~75, respectively.

Creation of MOFs with open metal sites by partial replacement of metal ions with different coordination numbers.

Herein, we developed isostructural metal-organic frameworks (MOFs) [Cu1-xPdx(SiF6)(bpy)2] (bpy: 4,4'-bipyridine) (SIFSIX-1-CuPd-3, -5 and -10) containing open metal sites using a partial metal-replacement approach. Starting from the SIFSIX-1-Cu-type MOF, some of the Cu2+ ions having octahedral geometry were successfully replaced with Pd2+ ions having square planar geometry in different ratios, while the framework structure was maintained. The results showed that gas adsorption properties of SIFSIX-1-Cu-type MOFs can be tuned via partial metal replacement.

Highly responsive nature of porous coordination polymer surfaces imaged by in situ atomic force microscopy.

The ability of porous coordination polymers to undergo reversible structural transformations in response to the presence of guest molecules has been intensively investigated for applications such as molecular separation, storage, sensing and signalling processes. Here we report on the direct observation of the highly guest-responsive nature of the surface of a single-crystalline porous coordination polymer, which consists of paddlewheel zinc clusters and two types of ligand, by in situ liquid-phase atomic force microscopy. Observations were carried out in solution at constant temperature (28 °C) by high-speed atomic force microscopy with lattice resolution.

Switchable gate-opening effect in metal-organic polyhedra assemblies through solution processing.

Gate-opening gas sorption is known for metal-organic frameworks, and is associated with structural flexibility and advantageous properties for sensing and gas uptake. Here, we show that gate-opening is also possible for metal-organic polyhedra (MOPs), and depends on the molecular organisation in the lattice. Thanks to the solubility of MOPs, several interchangeable solvatomorphs of a lantern-type MOP were synthesised treatment with different solvents.

Theoretical Insight into Gate-Opening Adsorption Mechanism and Sigmoidal Adsorption Isotherm into Porous Coordination Polymer.

The gate-opening adsorption mechanism and sigmoidal adsorption isotherm were theoretically investigated taking CO adsorption into porous coordination polymers, [Fe(ppt)] (PCP-N, Hppt = 3-(2-pyrazinyl)-5-(4-pyridyl)-1,2,4-triazole) and [Fe(dpt)] (PCP-C, Hdpt = 3-(2-pyridinyl)-5-(4-pyridyl)-1,2,4-triazole) as examples, where the hybrid method consisting of dispersion-corrected DFT for infinite PCP and a post-Hartree-Fock (SCS-MP2 and CCSD(T)) method for the cluster model was employed. PCP-N has site I (one-dimensional channel), site II (small aperture to site I), and site III (small pore) useful for CO adsorption. CO adsorption at site I occurs in a one by one manner with a Langmuir adsorption isotherm.

Readily accessible shape-memory effect in a porous interpenetrated coordination network.

Shape-memory effects are quite well-studied in general, but there is only one reported example in the context of porous materials. We report the second example of a porous coordination network that exhibits a sorbate-induced shape-memory effect and the first in which multiple sorbates, N, CO and CO promote this effect. The material, a new threefold interpenetrated pcu network, [Zn(4,4'-biphenyldicarboxylate)(1,4-bis(4-pyridyl)benzene)] (X-pcu-3-Zn-3i), exhibits three distinct phases: the as-synthesized α phase; a denser-activated β phase; and a shape-memory γ phase, which is intermediate in density between the α and β phases.