Twelve zeolitic imidazolate frameworks (ZIFs; termed ZIF-1 to -12) have been synthesized as crystals by copolymerization of either Zn(II) (ZIF-1 to -4, -6 to -8, and -10 to -11) or Co(II) (ZIF-9 and -12) with imidazolate-type links. The ZIF crystal structures are based on the nets of seven distinct aluminosilicate zeolites: tetrahedral Si(Al) and the bridging O are replaced with transition metal ion and imidazolate link, respectively. In addition, one example of mixed-coordination imidazolate of Zn(II) and In(III) (ZIF-5) based on the garnet net is reported. Study of the gas adsorption and thermal and chemical stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area ‫؍‬ 1,810 m 2 ͞g), high thermal stability (up to 550°C), and remarkable chemical resistance to boiling alkaline water and organic solvents.catalysis ͉ hydrogen storage ͉ metal-organic frameworks ͉ porosity ͉ zeolites A large segment of the global economy ($350 billion) is based on the use of crystalline microporous zeolites in petrochemical cracking, ion-exchange for water softening and purification, and in the separation of gases (1). Zeolite structures are composed of tetrahedral Si(Al)O 4 units covalently joined by bridging O atoms to produce Ͼ150 different types of framework (2). A long-standing challenge is to incorporate transition metal ions and organic units within their pores and, more desirably, to do so as an integral part of the zeolite framework. This ability would be useful in many catalytic applications because the pores would be lined with a high concentration of ordered transition metal sites whose electronic and steric properties can be tailored by functionalization of the organic links. However, the vision of achieving such a zeolite that combines these features remains largely unrealized. Here, we outline a general synthesis of structures having zeolite framework topologies in which all tetrahedral atoms are transition metals, and all bridging ones are imidazolate (IM) units.Imidazole can lose a proton to form IM, 1. In examining the dense-phases Co(IM) 2 and Zn(IM) 2 , whose structures are based on nets of linked CoN 4 or ZnN 4 tetrahedra (3, 4), we noticed that IM bridges make an M-IM-M angle, 1, close to 145°, which is coincident with the Si-O-Si angle, 2, which is preferred and commonly found in many zeolites (see Scheme 1). We believed that it should be possible under the right conditions to prepare metal IMs adopting open-framework zeolite structures. Indeed, a number of relatively new Fe(II) (5), Co(II) (6, 7), Cu(II) (8), and Zn(II) (9) IM compounds have structures that are based on zeolite-like tetrahedral nets. However, these materials are relatively dense (nonporous) and͞or low-symmetry structures. Only very recently, Zn(II) IMs having symmetrical porous structures analogous to zeolites were reported (10). Two of the aforementioned compounds are included, as zeolitic IM framework (ZIF)-7 and -8, among the library of ZIFs we report here (Fig. 1).** The focus of th...

Five porous metal-organic frameworks based on linking zinc oxide clusters with benzene-1,4-dicarboxylate, naphthalene-2,6-dicarboxylate, 4,5,9,10-tetrahydropyrene-2,7-dicarboxylate, 2,3,5,6-tetramethylbenzene-1,4-dicarboxylate, or benzene-1,3,5-tris(4-benzoate) were synthesized in gram-scale quantities to measure their hydrogen uptake properties. Hydrogen adsorption isotherms measured at 77 K show a distinct dependence of uptake on the nature of the link. At 1 atm, the materials sorb between 4.2 and 9.3 molecules of H2 per formula unit. The results imply a trend in hydrogen uptake with the number of rings in the organic moiety.

Five new metal–organic frameworks (MOFs, termed MOF-324, 325, 326 and IRMOF-61 and 62) of either short linkers (pyrazolecarboxylate and pyrazaboledicarboxylate) or long and thin alkyne functionalities (ethynyldibenzoate and butadiynedibenzoate) were prepared to examine their impact on hydrogen storage in MOFs. These compounds were characterized by single-crystal X-ray diffraction, and their low-pressure and high-pressure hydrogen uptake properties were investigated. In particular, volumetric excess H2 uptake by MOF-324 and IRMOF-62 outperforms MOF-177 up to 30 bar. Inelastic neutron-scattering studies for MOF-324 also revealed strong interactions between the organic links and hydrogen, in contrast to MOF-5 where the interactions between the Zn4O unit and hydrogen are the strongest. These data also show that smaller pores and polarized linkers in MOFs are indeed advantageous for hydrogen storage.

Graphical abstract

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 e...

Enhancement of hydrolytic stability of metal–organic frameworks (MOFs) is a challenging issue in MOF chemistry because most MOFs have shown limitations in their applications under a humid environment. Meanwhile, inner sphere electron transfer has constituted one of the most intensively studied subjects in contemporary chemistry. In this report, we show, for the first time, a new conceptual coordinative reduction of Cu2+ ion, which is realized in a paddlewheel MOF, HKUST-1, with a postsynthetic manner via inner sphere “single” electron transfer from hydroquinone (H2Q) to Cu2+ through its coordination bond. H2Q treatment of HKUST-1 under anhydrous conditions leads to the single charge (1+) reduction of approximately 30% of Cu2+ ions. Thus, this coordinative reduction is an excellent reduction process to be self-controlled in both oxidation state and quantity. As described below, once Cu2+ ions are reduced to Cu+, the reduction reaction does not proceed further, in terms of their oxidation state as well as their amount. Also, we demonstrate that a half of the Cu+ ions (about 15%) remains in paddlewheel framework with pseudo square planar geometry and the other half of the Cu+ ions (about 15%) forms [Cu­(MeCN)4]+ complex in a small cage in the fashion of a ship-in-a-bottle after dissociation from the framework. Furthermore, we show that the coordinative reduction results in substantial enhancement of the hydrolytic stability of HKUST-1 to the extent that its structure remains intact even after exposure to humid air for two years.

† Electronic supplementary information (ESI) available: Materials synthesis methods (COFs and ZIFs), PXRD data, N 2 BET, high-resolution low-pressure H 2 BET measurement and evaluation of isosteric heat of adsorption. See

A photocatalyst heterogenized in discrete cages of metal–organic polyhedra provides highly active and robust conversion of carbon dioxide.