Pepped up: Notwithstanding the intrinsic conformational flexibility of peptides, [Zn(Gly-Thr)(2)] behaves as a robust porous metal-organic framework thanks to the rigidity introduced by the use of Gly-Thr (see scheme). This rigidity arises from the sequence of amino acids in the dipeptide that locks its conformational flexibility in the framework.

Heteroepitaxial growth of BaSnO3 and Ba1−xLaxSnO3 (x = 7%) lanthanum doped barium stannate thin films on different perovskite single crystal (SrTiO3 (001) and SmScO3 (110)) substrates has been achieved by pulsed laser deposition under optimized deposition conditions. X-ray diffraction measurements indicate that the films on either of these substrates are relaxed due to the large mismatch and present a high degree of crystallinity with narrow rocking curves and smooth surface morphology while analytical quantification by proton induced X-ray emission confirms the stoichiometric La transfer from a polyphasic target, producing films with measured La contents above the bulk solubility limit. The films show degenerate semiconducting behavior on both substrates, with the observed room temperature resistivities, Hall mobilities, and carrier concentrations of 4.4 mΩ cm, 10.11 cm2 V−1 s−1, and 1.38 × 1020 cm−3 on SmScO3 and 7.8 mΩ cm, 5.8 cm2 V−1 s−1, and 1.36 × 1020 cm−3 on SrTiO3 ruling out any extrinsic contribution from the substrate. The superior electrical properties observed on the SmScO3 substrate are attributed to reduction in dislocation density from the lower lattice mismatch.

Epitaxial thin films of the 10 layer cubic perovskite superstructure Ba 1.7 Ca 2.4 Y 0.9 Fe 5 O 13 were grown by pulsed laser deposition, retaining the six distinct cation sites found in the bulk material. Growth on single crystal strontium titanate (STO) (0 0 1) substrates changes the observed symmetry from orthorhombic to tetragonal and orients the layer stacking direction of the superstructure normal to the substrate plane. The material is a candidate cathode for solid oxide fuel cells (SOFCs) and in the intermediate temperature (IT) region at 600 C we measure the in-plane AC conductivity of the thin film as 30 S cm À1 , significantly enhanced over 3.5 S cm À1 found for the polycrystalline form. This is assigned to reduction of the grain boundary density and alignment of the planes predicted to have the highest electronic and ionic conductivities. High resolution electron microscopy measurements demonstrate the atomic site ordering producing the superstructure and reveal defects associated with stacking faults in the ordering sequence.

Metal-organic frameworks (MOFs) are a class of crystalline materials built up from the interconnection of organic linkers and metal nodes. [1] The judicious choice of these organic and inorganic synthons and the control exerted on their spatial arrangement enables fine-tuning of their intrinsic porosity and accessible surface area. This controllable structure-tofunction relationship, together with their extraordinary structural and chemical versatility, have resulted in the evaluation of these porous coordination polymers in applications such as gas storage and separation, [2] heterogeneous catalysis, [3] and sensing. [4] Within this general family, the development of open frameworks from biologically derived molecules deserves particular attention. To date, the incorporation of amino acids [5] or nucleobases [6] has been demonstrated to be a fruitful route towards the design of bio-analogous MOFs. [7] In this context, the use of oligopeptides has recently led to adaptable porosity in [Zn(Gly-Ala) 2 ], [8] in which the flexibility of the peptide linker adapts the pore conformation to the nature and loading of guest through its thermally accessible manifold of torsions. This scenario contrasts with that encountered in rigid frameworks, where the use of more torsionally restricted linkers limits the host ability to rearrange. We believe that a deeper understanding of the role played by more rigid dipeptide connectors is important for the development of a next generation of biomimetic porous materials since the combination of both types of components, dynamic and rigid, determines the structural flexibility in proteins and controls their folding/unfolding dynamics that determines their biological function. [9] Here we describe [Zn(Gly-Thr) 2 ]·CH 3 OH (1) assembled from Zn 2+ ions and the dipeptide glycilthreonine (Gly-Thr). Besides exhibiting selective adsorption of CO 2 in preference to CH 4 , this 2D layered framework displays 1D porosity and retains crystallinity upon solvent removal. This scenario contrasts with the poor structural stability generally attributed to peptide-based materials. We show how this compromise between flexibility and structural stability can be achieved by precise control of the coordination modes and supramolecular interactions enabled by the peptide, hence opening the door for the design of a next generation of robust adaptable porous materials.Colorless crystals of 1 were isolated from the reaction of zinc nitrate and Gly-l-Thr in a methanolic solution, slightly basified with aqueous NaOH (see Supporting Information S1 for further details). This synthetic route is almost equivalent to that described for the related [Zn(Gly-Ala) 2 ], [8] hence indicating that the synthetic versatility generally attributed to MOF chemistry can be also associated with these peptidic coordination polymers.

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