Disorder and Sorption Preferences in a Highly Stable Fluoride-Containing Rare-Earth -Type Metal-Organic Framework.

Rare-earth (RE) metal-organic frameworks (MOFs) synthesized in the presence of fluorine-donating modulators or linkers are an important new subset of functional MOFs. However, the exact nature of the REX core of the molecular building block (MBB) of the MOF, where X is a μ-bridging group, remains unclear. Investigation of one of the archetypal members of this family with the stable framework topology, Y-fum--MOF (), using a combination of experimental techniques, including high-field (20 T) solid-state nuclear magnetic resonance spectroscopy, has determined two sources of framework disorder involving the μ-X face-capping group of the MBB and the fumarate (fum) linker.

Breathing Behaviour Modification of Gallium MIL-53 Metal-Organic Frameworks Induced by the Bridging Framework Inorganic Anion.

Controlling aspects of the μ -X bridging anion in the metal-organic framework Ga-MIL-53 [GaX(bdc)] (X =(OH) or F , bdc=1, 4-benzenedicarboxylate) is shown to direct the temperature at which thermally induced breathing transitions of this framework occur. In situ single crystal X-ray diffraction studies reveal that substituting 20 % of (OH) in [Ga(OH)(bdc)] (1) for F to produce [Ga(OH) F (bdc)] (2) stabilises the large pore (lp) form relative to the narrow pore (np) form, causing a well-defined decrease in the onset of the lp to np transition at higher temperatures, and the adsorption/desorption of nitrogen at lower temperatures through np to lp to intermediate (int) pore transitions. These in situ diffraction studies have also yielded a more plausible crystal structure of the int-[GaX(bdc)] ⋅ H O phases and shown that increasing the heating rate to a flash heating regime can enable the int-[GaX(bdc)] ⋅ H O to lp-[GaX(bdc)] transition to occur at a lower temperature than np-[GaX(bdc)] via an unreported pathway.

Bimetallic Aluminum- and Niobium-Doped MCM-41 for Efficient Conversion of Biomass-Derived 2-Methyltetrahydrofuran to Pentadienes.

The production of conjugated C4-C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)-atomically doped mesoporous silica, denoted as AlNb-MCM-41, which affords quantitative conversion of 2-methyltetrahydrofuran (2-MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of Al and Nb sites into the framework of AlNb-MCM-41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure.

The development of a comprehensive toolbox based on multi-level, high-throughput screening of MOFs for CO/N separations.

The separation of CO/N mixtures is a challenging problem in the petrochemical sector due to the very similar physical properties of these two molecules, such as size, molecular weight and boiling point. To solve this and other challenging gas separations, one requires a holistic approach. The complexity of a screening exercise for adsorption-based separations arises from the multitude of existing porous materials, including metal-organic frameworks.

Crystal growth of the core and rotated epitaxial shell of a heterometallic metal-organic framework revealed with atomic force microscopy.

Atomic force microscopy has been used to determine the surface crystal growth of two isostructural metal-organic frameworks, [Zn(ndc)(dabco)] (ndc = 1,4-naphthalenedicarboxylate, dabco = 4-diazabicyclo[2.2.2]octane) (1) and [Cu(ndc)(dabco)] (2), from a core crystal of 1 for the former and a core-shell 1@2 crystal for the latter.

: a generic computer program for Monte Carlo modelling of crystal growth.

A Monte Carlo crystal growth simulation tool, , is described which is able to simultaneously model both the crystal habit and nanoscopic surface topography of any crystal structure under conditions of variable supersaturation or at equilibrium. This tool has been developed in order to permit the rapid simulation of crystal surface maps generated by scanning probe microscopies in combination with overall crystal habit. As the simulation is based upon a coarse graining at the nanoscopic level features such as crystal rounding at low supersaturation or undersaturation conditions are also faithfully reproduced.

Control of zeolite microenvironment for propene synthesis from methanol.

Optimising the balance between propene selectivity, propene/ethene ratio and catalytic stability and unravelling the explicit mechanism on formation of the first carbon-carbon bond are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the nature of active sites within the pores of commercial MFI-zeolites by incorporating tantalum(V) and aluminium(III) centres into the framework. The resultant TaAlS-1 zeolite exhibits simultaneously remarkable propene selectivity (51%), propene/ethene ratio (8.

Unveiling the mechanism of lattice-mismatched crystal growth of a core-shell metal-organic framework.

Determining the effect of severe lattice mismatch on the crystal growth mechanism and form of epitaxially grown materials is vital to understand and direct the form and function of such materials. Herein, we report the use of atomic force microscopy to reveal the growth of a shell metal-organic framework (MOF) on all faces of a core MOF that has similar , -lattice parameters but a ∼32% mismatch in the -lattice parameter. The work shows the mechanism through which the shell MOF overcomes the core terrace height mismatch depends on that mismatch being reduced before overgrowth of continuous shell layers can occur.

Binding CO by a Cr Metallacrown.

The {Cr } metallacrown [CrF(O C Bu) ] , containing a F-lined internal cavity, shows high selectivity for CO over N . DFT calculations and absorption studies support the multiple binding of F-groups to the C-center of CO (C⋅⋅⋅F 3.190(9)-3.

Predicting crystal growth via a unified kinetic three-dimensional partition model.

Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested.

Synthesis and Transport Properties of Novel MOF/PIM-1/MOF Sandwich Membranes for Gas Separation.

Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes.

Determination of the Preassembled Nucleating Units That Are Critical for the Crystal Growth of the Metal-Organic Framework CdIF-4.

Identifying the form and role of the chemical species that traverse the stages of crystallization is critical to understanding the formation process of coordination polymers. Herein, we report the combined use of in situ atomic force microscopy and mass spectrometry to identify preformed, complex, cadmium 2-ethylimidazole containing solution species in the growth solution of the cadmium 2-ethylimidazolate metal-organic framework CdIF-4, and show that they are critical in the surface nucleation for the crystal growth of this material. Surface nucleation appears to be instigated by these [Cdx (CH3 CO2 )y (C5 H7 N2 /C5 H8 N2 )z ]-containing solution species and not by sole addition of the ligand molecules.

Anatomy of screw dislocations in nanoporous SAPO-18 as revealed by atomic force microscopy.

Defects in solids are often the source of functional activity, the trigger for crystal growth and the seat of instability. Screw dislocations are notoriously difficult to study by electron microscopy. Here we decipher the complex anatomy of one such defect in the industrially important nanoporous catalyst SAPO-18 by atomic force microscopy.

Atomic force microscopy of novel zeolitic materials prepared by top-down synthesis and ADOR mechanism.

Top-down synthesis of 2D materials from a parent 3D zeolite with subsequent post-synthetic modification is an interesting method for synthesis of new materials. Assembly, disassembly, organisation, reassembly (ADOR) processes towards novel materials based on the zeolite UTL are now established. Herein, we present the first study of these materials by atomic force microscopy (AFM).

Materials discovery and crystal growth of zeolite A type zeolitic-imidazolate frameworks revealed by atomic force microscopy.

A new zeolitic-imidazolate framework (ZIF), [Zn(imidazolate)2-x(benzimidazolate)x], that has the zeolite A (LTA) framework topology and contains relatively inexpensive organic linkers has been revealed using in situ atomic force microscopy. The new material was grown on the structure-directing surface of [Zn(imidazolate)1.5(5-chlorobenzimidazolate)0.

Crystal growth mechanisms and morphological control of the prototypical metal-organic framework MOF-5 revealed by atomic force microscopy.

Crystal growth of the metal-organic framework MOF-5 was studied by atomic force microscopy (AFM) for the first time. Growth under low supersaturation conditions was found to occur by a two-dimensional or spiral crystal growth mechanism. Observation of developing nuclei during the former reveals growth occurs through a process of nucleation and spreading of metastable and stable sub-layers revealing that MOFs may be considered as dense phase structures in terms of crystal growth, even though they contain sub-layers consisting of ordered framework and disordered non-framework components.

Growth mechanism of microporous zincophosphate sodalite revealed by in situ atomic force microscopy.

Microporous zincophosphate sodalite crystal growth has been studied in situ by atomic force microscopy. This simple model system permits an in depth investigation of some of the axioms governing crystal growth of nanoporous framework solids in general. In particular, this work reveals the importance of considering the growth of a framework material as the growth of a dense phase material where the framework structure, nonframework cations, and hydrogen-bonded water must all be considered.

Crystal growth of nanoporous metal organic frameworks.

Nanoporous metal organic frameworks (MOFs) form one of the newest families of crystalline nanoporous material that is receiving worldwide attention. Successful use of MOFs for application requires not only development of new materials but also a need to control their crystal properties such as size, morphology, and defect concentration. An understanding of the crystal growth processes is necessary in order to aid development of routes to control such properties of the crystallites.

Revelation of the molecular assembly of the nanoporous metal organic framework ZIF-8.

Crystalline nanoporous materials are one of the most important families of complex functional material. Many questions pertaining to the molecular assembly mechanism of the framework of these materials remain unanswered. Only recently has it become possible to answer definitively some of these questions by observation of growing nanoscopic surface features on metal organic frameworks (MOFs) through use of in situ atomic force microscopy (AFM).

Structural variety within gallium diphosphonates affected by the organic linker length.

Three new gallium diphosphonates: Ga(3)(OH)(O(3)PC(3)H(6)PO(3))(2) (1), Ga(4)(O(3)PC(5)H(10)PO(3))(3)(C(5)H(5)N)(2) (2), and Ga(HO(3)PC(10)H(20)PO(3)) (3), in which the diphosphonate bridging ligands have 3, 5, and 10 methylene units, respectively, have been synthesized using solvothermal methods and their structures determined using single-crystal laboratory and synchrotron X-ray diffraction data. All three materials contain Ga-centered tetrahedra and octahedra linked together through the -PO(3) groups of the diphosphonate ligands to form two-dimensional pillared slab (1) and three-dimensional pillared (2 and 3) materials. Compound 1 contains bridging hydroxide anions that connect Ga-centered octahedra and tetrahedra, and contains pillared slabs in which one side of the Ga-P-O/OH/CH hybrid layers are connected by the propylenediphosphonate groups only.

Single layer growth of sub-micron metal-organic framework crystals observed by in situ atomic force microscopy.

In situ atomic force microscopy was used to directly investigate the growth processes of the oriented metal-organic framework HKUST-1 grown on self-assembled monolayers on gold.