The synthesis of Li(x)BC (x > 0.5) by high temperature Li deintercalation from LiBC is demonstrated by refinement of X-ray and neutron powder diffraction data--contrary to theoretical expectation no superconductivity above 2K is observed in these materials.

The peptide-based porous 3D framework, ZnCar, has been synthesized from Zn 2+ and the natural dipeptide carnosine (b-alanyl-l-histidine). Unlike previous extended peptide networks, the imidazole side chain of the histidine residue is deprotonated to afford Zn-imidazolate chains, with bonding similar to the zeolitic imidazolate framework (ZIF) family of porous materials. ZnCar exhibits permanent microporosity with a surface area of 448 m 2 g À1 , and its pores are 1D channels with 5 openings and a characteristic chiral shape. This compound is chemically stable in organic solvents and water. Single-crystal X-ray diffraction (XRD) showed that the ZnCar framework adapts to MeOH and H 2 O guests because of the torsional flexibility of the main His-b-Ala chain, while retaining the rigidity conferred by the Zn-imidazolate chains. The conformation adopted by carnosine is driven by the H bonds formed both to other dipeptides and to the guests, permitting the observed structural transformations.Metal-organic frameworks (MOFs) are crystalline porous materials composed of inorganic nodes, either single ions or clusters of ions, bridged by organic linkers through metalligand coordination bonds.[1] Recently, several biomolecules, such as amino acids, [2] nucleobases, [3] saccharides, [4] and peptides, [5] were used as organic linkers in MOF synthesis, mainly because of the diversity of their metal binding sites. The incorporation of biomolecules in MOFs also attracts particular attention because they can improve the biocompatibility of the final products, enhance the structural and chemical diversity of the internal surfaces of MOFs, and afford chiral frameworks that may have unique separation and catalytic properties. [6] Peptides are particularly interesting as linkers because dipeptides with hydrophobic residues that are held together by H bonds form metal-free purely peptide-based porous materials. These structures are divided into two groups, the Val-Ala compounds with hydrophobic pores and the Phe-Phe compounds with hydrophilic pores.[7] The Val-Ala structures exhibit typical CO 2 and CH 4 adsorption for microporous materials. [8] In MOFs, peptides have the ability to act as connecting ligands as they have at least one amino and one carboxylic acid terminus that can coordinate metal ions. The dipeptides Gly-Ala and Gly-Thr thus connect Zn 2+ ions to form two topologically distinct 2D-layered framework compounds, Zn(Gly-Ala) 2 and Zn(Gly-Thr) 2 , respectively.[9] The former is a flexible porous material that displays an adaptable pore conformation, which evolves continuously from an open to a partially disordered closed structure in response to the level of guest loading. The latter is structurally rigid to guest loss in a manner characteristic of rigid MOFs and exhibits permanent porosity with a surface area of 200 m 2 g À1 after solvent removal, as the framework is stabilized by the additional H bonding between the OH functional group from the threonine side chain and the NH 2 terminal group. These two examp...

Flexible metal–organic frameworks (MOFs) undergo structural transformations in response to physical and chemical stimuli. This is hard to control because of feedback between guest uptake and host structure change. We report a family of flexible MOFs based on derivatized amino acid linkers. Their porosity consists of a one-dimensional channel connected to three peripheral pockets. This network structure amplifies small local changes in linker conformation, which are strongly coupled to the guest packing in and the shape of the peripheral pockets, to afford large changes in the global pore geometry that can, for example, segment the pore into four isolated components. The synergy among pore volume, guest packing, and linker conformation that characterizes this family of structures can be determined by the amino acid side chain, because it is repositioned by linker torsion. The resulting control optimizes noncovalent interactions to differentiate the uptake and structure response of host–guest pairs with similar chemistries.

The chemically directed structure evolution method uses chemical models to quantify the environment of atoms and vacancy sites in a crystal structure with that information used to inform how to modify the structure for crystal structure prediction.

Materials that bind strongly to water structure the contact layer, modifying its chemical and physical properties in a manner that depends on the symmetry and reactivity of the surface. Although detailed models have been developed for several inert surfaces, much less is known about reactive surfaces, particularly those with a symmetry different from that of ice. Here we investigate water adsorption on a rectangular surface, Ni(110), an active re-forming catalyst that interacts strongly with water. Instead of forming a network of H-bonded cyclic rings, water forms flat 1D water chains, leaving half the Ni atoms exposed. Second layer water also follows the surface symmetry, forming chains of alternating pentamer and heptamer rings in preference to an extended 2D structure. This behavior is different from that found on other surfaces studied previously and is driven by the short lattice spacing of the solid and the strength of the Ni–water bond.