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High-resolution atomic force microscopy (AFM) imaging of a metal-oxide framework (MOF) surface is demonstrated by analyzing both in air and under ultra high vacuum (UHV) conditions. The comparison of the results with the previous AFM study has shown a much higher structural quality of MOF crystals grown on the substrate and in contrast to the conventional method.

An approximately functionalized organic surface is used as a two-dimensional nucleation site for growing metal-organic framework (MOF) structures in a step-by-step method. This step has also provided an opportunity for growing novel MOF-like ordered structures consisting of alternating layers, with nonperiodic combinations of different metal ions and different linkers.

The time-resolved static light scattering (TLS) is used to investigate the homogeneous nucleation and crystal growth of [[Zn.sub.4]O[(bdc).sub.3]] in diethylformamide (DEE) at variable conditions and in the presence of certain additives. The addition of p-perfluoroethylbenzoic acid as capping reagent has yielded stable size-selected metal-organic open framework 5 (MOF-5) colloids and has described a general concept for controlled particle formation of carboxylic acid based MOFs in solution.

A smallangle neutron scattering (SANS) study is presented, whichinvestigates the impact of a modulator on nucleation and growth ofMOF-5 nanoparticles. Two DMF solutions, one with the secondary buildingunit Zn4O(C6H5COO)6(SBU)and one with terephthalic acid (BDC) as a linker, were mixed, and 5 min after generation of the mixture, monodentate 4-n-decylbenzoic acid was added as a modulator agent. Time-resolvedSANS during the initial stages of the particle formation process offeredinsight into morphological transformations during the first hours. Subsequently, it could be demonstrated that a shell is formed by themodulator wrapping around the growing MOF-5 particles while directingthe formation of MOF-5 nanoparticles. This has been made possibleby an identification of a mixture of deuterated and hydrogenated solvent(DMF), which matches the scattering contrast of MOF-5, thus givingaccess to the scattering signal of the modulator. [ABSTRACT FROM AUTHOR]

The deposition of five isostructural PCPs from the CPO-27-M (M = Ni, Co, Mg, Zn and Mn) family on top of amorphous Al2O3was studied. The coatings were grown directly out of solvothermal mother solutions prepared following published procedures. Powder X-ray diffraction and scanning electron microscopy studies showed that when enough surface binding sites are available, continuous and uniform coatings of phase-pure CPO-27-Ni, Co and Mg are obtained. In the case of CPO-27-Zn and Mn, large crystals are spread onto the surface in a non-continuous fashion. The different morphologies suggest a strong effect of the cation nature on the growth mechanism and binding to the substrate. Activation and loading experiments were also performed in order to check the porosity of the films. [ABSTRACT FROM AUTHOR]

The formation of [Cu3(btc)2] (HKUST-1; btc = 1,3,5-benzenetricarboxylate) nanocrystals from a super-saturated mother solution at room temperature was monitored by time-resolved light scattering (TLS); the system is characterized by a rapid growth up to a size limit of 200 nm within a few minutes, and the size and shape of the crystallites were also determined by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Abstract: Metal-organic framework (MOF) membranes were prepared by stepwise deposition of reactants. Two pillared layered MOFs with the general formula [Cu2L2P] n (L=dicarboxylate linker, P=pillaring ligand) were selected. Within this family, fine tuning of adsorption affinity and pore size is possible by variation or functionalization of the L and P linkers. Compound 1 was chosen to be non-polar (L=1,4-naphtalenedicarboxylate=ndc, P=1,4-diazabicyclo(2.2.2)octane=dabco); in contrast, compound 2 included a polar linker L with two conformationally flexible ether side chains (L=2,5-bis(2-methoxyethoxy)-1,4-benzene-dicarboxylate=BME-bdc, P=dabco). The polar functionalization is expected to increase the framework affinity for CO2 compared to CH4. The step-by-step, liquid phase deposition of 1 and 2 resulted in pore-plugging of macroporous ceramic supports. The performances of the two MOF membranes were evaluated in gas separation experiments of equimolar CO2/CH4 mixtures using a modified Wicke–Kallenbach technique. Anti-Knudsen CO2/CH4 separation factors in the range of ∼4–4.5 were obtained for the membrane consisting of the polar 2, whereas the separation of the membrane formed from the non-polar 1 was found to be Knudsen-like. [Copyright &y& Elsevier]

The article presents a study on high-resolution atomic force microscopy (AFM) as a more effective approach to surface analysis of metal-organic frameworks (MOFs). It states that the AFM analysis was performed on the top surface of a single Cu3(BTC)2 microcrystal. It mentions that the crystals evaluated in the study are essentially free from screw dislocation and exhibit large micrometer-sized terraces with a homogenous termination.

The progressive liquid-phase layer-by-layer (LbL) growth of anisotropic multicomponent layer-based porous coordination polymers (PCPs) of the general formula [M(L)(P)(0.5)] (M: Cu(2+), Zn(2+); L: dicarboxylate linker; P: dinitrogen pillar ligand) was investigated by using either pyridyl- or carboxyl-terminated self-assembled monolayers (SAMs) on gold substrates as templates. It was found that the deposition of smooth, highly crystalline, and oriented multilayer films of these PCPs depends on the conditions at the early growth cycles. In the case of a two-step process with an equimolar mixture of L and P, growth along the [001] direction is strongly preferred. However, employing a three-step scheme with full separation of all components allows deposition along the [100] direction on carboxyl-terminated SAMs. Interestingly, the growth of additional layers on top of previously grown oriented seeding layers proved to be insensitive to the particular growth scheme and full retention of the initial orientation, either along the [001] or [100] direction, was observed. This homo- and heteroepitaxial LbL growth allows full control over the orientation and the layer sequence, including introduction of functionalized linkers and pillars., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal-organic frameworks (MOFs) are a fascinating class of novel inorganic-organic hybrid materials. They are essentially based on classic coordination chemistry and hold much promise for unique applications ranging from gas storage and separation to chemical sensing, catalysis, and drug release. The evolution of the full innovative potential of MOFs, in particular for nanotechnology and device integration, however requires a fundamental understanding of the formation process of MOFs. Also necessary is the ability to control the growth of thin MOF films and the positioning of size- and shape-selected crystals as well as MOF heterostructures on a given surface in a well-defined and oriented fashion. MOFs are solid-state materials typically formed by solvothermal reactions and their crystallization from the liquid phase involves the surface chemistry of their building blocks. This Review brings together various key aspects of the surface chemistry of MOFs.

One step at a time: The in situ monitoring of the step-by-step formation of metal-organic frameworks (MOFs) by using surface plasmon resonance (SPR), allows the nucleation process and the formation of the secondary building units to be investigated. Growth rates on functionalized organic surfaces with different crystallographic orientations can also be studied.