Showing papers by "Omar M. Yaghi published in 2016"
TL;DR: This work describes the synthesis and crystal structures of three porous ZIFs that are expanded analogues of zeolite A; their cage walls are functionalized, and their metal ions can be changed without changing the underlying LTA topology.
Abstract: The disclosure provides for multivariant zeolitic imidazolate frameworks (ZIFs), methods of making thereof, and methods of use therefrom.
881 citations
TL;DR: Some scores of rod MOF structures are illustrated and deconstructed into their underlying nets in this way, and Crystallographic data for all nets in their maximum symmetry embeddings are provided.
Abstract: Rod MOFs are metal–organic frameworks in which the metal-containing secondary building units consist of infinite rods of linked metal-centered polyhedra. For such materials, we identify the points of extension, often atoms, which define the interface between the organic and inorganic components of the structure. The pattern of points of extension defines a shape such as a helix, ladder, helical ribbon, or cylinder tiling. The linkage of these shapes into a three-dimensional framework in turn defines a net characteristic of the original structure. Some scores of rod MOF structures are illustrated and deconstructed into their underlying nets in this way. Crystallographic data for all nets in their maximum symmetry embeddings are provided.
654 citations
TL;DR: A three-dimensional covalent organic framework constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)-bisphenanthroline tetrafluoroborate, Cu(PDB)2(BF4), and benzidine (BZ).
Abstract: A three-dimensional covalent organic framework (COF-505) constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)-bisphenanthroline tetrafluoroborate, Cu(PDB)2(BF4), and benzidine (BZ). The copper centers are topologically independent of the weaving within the COF structure and serve as templates for bringing the threads into a woven pattern rather than the more commonly observed parallel arrangement. The copper(I) ions can be reversibly removed and added without loss of the COF structure, for which a tenfold increase in elasticity accompanies its demetalation. The threads in COF-505 have many degrees of freedom for enormous deviations to take place between them, throughout the material, without undoing the weaving of the overall structure.
364 citations
TL;DR: In this paper, the role of metal-organic frameworks for the capture, storage and conversion of gases such as hydrogen, methane and carbon dioxide is explored. But the authors focus on metal oxide "hubs" are linked with organic "struts" to make materials of ultrahigh porosity, which provide a basis for addressing this challenge through materials design on the molecular level.
Abstract: Reducing society's reliance on fossil fuels presents one of the most pressing energy and environmental challenges facing our planet. Hydrogen, methane and carbon dioxide, which are some of the smallest and simplest molecules known, may lie at the centre of solving this problem through realization of a carbon-neutral energy cycle. Potentially, this could be achieved through the deployment of hydrogen as the fuel of the long term, methane as a transitional fuel, and carbon dioxide capture and sequestration as the urgent response to ongoing climate change. Here we detail strategies and technologies developed to overcome the difficulties encountered in the capture, storage, delivery and conversion of these gas molecules. In particular, we focus on metal–organic frameworks in which metal oxide ‘hubs’ are linked with organic ‘struts’ to make materials of ultrahigh porosity, which provide a basis for addressing this challenge through materials design on the molecular level. The capture, storage and conversion of gases such as hydrogen, methane and carbon dioxide may play a key role in the provision of carbon-neutral energy. This Review explores the role of metal–organic frameworks — porous networks of metal ions or clusters connected by organic linkers — for such applications.
346 citations
TL;DR: The X-ray photoelectron spectroscopy data obtained on the surface of the catalyst show that Zr 3d binding energy is shifted toward lower oxidation state in the presence of Cu NC, suggesting that there is a strong interaction between Cu NC and Zr oxide SBUs of the MOF to make a highly active Cu catalyst.
Abstract: We show that the activity and selectivity of Cu catalyst can be promoted by a Zr-based metal–organic framework (MOF), Zr6O4(OH)4(BDC)6 (BDC = 1,4-benzenedicarboxylate), UiO-66, to have a strong interaction with Zr oxide [Zr6O4(OH)4(−CO2)12] secondary building units (SBUs) of the MOF for CO2 hydrogenation to methanol. These interesting features are achieved by a catalyst composed of 18 nm single Cu nanocrystal (NC) encapsulated within single crystal UiO-66 (Cu⊂UiO-66). The performance of this catalyst construct exceeds the benchmark Cu/ZnO/Al2O3 catalyst and gives a steady 8-fold enhanced yield and 100% selectivity for methanol. The X-ray photoelectron spectroscopy data obtained on the surface of the catalyst show that Zr 3d binding energy is shifted toward lower oxidation state in the presence of Cu NC, suggesting that there is a strong interaction between Cu NC and Zr oxide SBUs of the MOF to make a highly active Cu catalyst.
330 citations
TL;DR: This work demonstrates (a) the first chemical conversion of a COF linkage and (b) how the usual "crystallization problem" encountered in COF chemistry can be bypassed to access COFs, such as these amides, that are typically thought to be difficult to obtain by the usual de novo methods.
Abstract: The imine linkages of two layered, porous covalent organic frameworks (COFs), TPB-TP-COF ([C6H3(C6H4N)3]2[C6H4(CH)2]3, 1) and 4PE-1P-COF ([C2(C6H4N)4][C6H4(CH)2]2, 2), have been transformed into amide linkages to make the respective isostructural amide COFs 1′ and 2′ by direct oxidation with retention of crystallinity and permanent porosity. Remarkably, the oxidation of both imine COFs is complete, as assessed by FT-IR and 13C CP-MAS NMR spectroscopy and demonstrates (a) the first chemical conversion of a COF linkage and (b) how the usual “crystallization problem” encountered in COF chemistry can be bypassed to access COFs, such as these amides, that are typically thought to be difficult to obtain by the usual de novo methods. The amide COFs show improved chemical stability relative to their imine progenitors.
309 citations
TL;DR: Metal-organic frameworks are exemplars of how covalent chemistry has led to porosity with designed metrics and functionality, chemically-rich sequences of information within their frameworks, and well-defined mesoscopic constructs in which nanoMOFs enclose inorganic nanocrystals and give them new levels of spatial definition, stability, and functionality.
Abstract: Linking molecular building units by covalent bonds to make crystalline extended structures has given rise to metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), thus bringing the precision and versatility of covalent chemistry beyond discrete molecules to extended structures. The key advance in this regard has been the development of strategies to overcome the “crystallization problem”, which is usually encountered when attempting to link molecular building units into covalent solids. Currently, numerous MOFs and COFs are made as crystalline materials in which the large size of the constituent units provides for open frameworks. The molecular units thus reticulated become part of a new environment where they have (a) lower degrees of freedom because they are fixed into position within the framework; (b) well-defined spatial arrangements where their properties are influenced by the intricacies of the pores; and (c) ordered patterns onto which functional groups can be covalently attached...
296 citations
TL;DR: The scope of MOF materials with ultrahigh working capacity to include linkers having the common acrylate connectivity is expanded, and MOF-905 is among the best performing methane storage materials with a volumetric working capacity rivaling that of HKUST-1.
Abstract: High methane storage capacity in porous materials is important for the design and manufacture of vehicles powered by natural gas. Here, we report the synthesis, crystal structures and methane adsorption properties of five new zinc metal–organic frameworks (MOFs), MOF-905, MOF-905-Me2, MOF-905-Naph, MOF-905-NO2, and MOF-950. All these MOFs consist of the Zn4O(−CO2)6 secondary building units (SBUs) and benzene-1,3,5-tri-β-acrylate, BTAC. The permanent porosity of all five materials was confirmed, and their methane adsorption measured up to 80 bar to reveal that MOF-905 is among the best performing methane storage materials with a volumetric working capacity (desorption at 5 bar) of 203 cm3 cm–3 at 80 bar and 298 K, a value rivaling that of HKUST-1 (200 cm3 cm–3), the benchmark compound for methane storage in MOFs. This study expands the scope of MOF materials with ultrahigh working capacity to include linkers having the common acrylate connectivity.
235 citations
232 citations
TL;DR: This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs.
Abstract: A crystalline material with a two-dimensional structure, termed metal–organic framework-901 (MOF-901), was prepared using a strategy that combines the chemistry of MOFs and covalent–organic frameworks (COFs). This strategy involves in situ generation of an amine-functionalized titanium oxo cluster, Ti6O6(OCH3)6(AB)6 (AB = 4-aminobenzoate), which was linked with benzene-1,4-dialdehyde using imine condensation reactions, typical of COFs. The crystal structure of MOF-901 is composed of hexagonal porous layers that are likely stacked in staggered conformation (hxl topology). This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs. The incorporation of Ti(IV) units made MOF-901 useful in the photocatalyzed polymerization of methyl methacrylate (MMA). The resulting polyMMA product was obtained with a high-number-average molar mass (26 850 g mol–1) and low ...
227 citations
TL;DR: Seven post-synthetic reactions can be successfully achieved within the pores of a multivariate MOF, MTV-IRMOF-74-III, to covalently incorporate tripeptides that resemble the active sites of enzymes in their spatial arrangement and compositional heterogeneity.
Abstract: The design of enzyme-like complexity within metal-organic frameworks (MOFs) requires multiple reactions to be performed on a MOF crystal without losing access to its interior. Here, we show that seven post-synthetic reactions can be successfully achieved within the pores of a multivariate MOF, MTV-IRMOF-74-III, to covalently incorporate tripeptides that resemble the active sites of enzymes in their spatial arrangement and compositional heterogeneity. These reactions build up H2N-Pro-Gly-Ala-CONHL and H2N-Cys-His-Asp-CONHL (where L = organic struts) amino acid sequences by covalently attaching them to the organic struts in the MOFs, without losing porosity or crystallinity. An enabling feature of this chemistry is that the primary amine functionality (-CH2NHBoc) of the original MOF is more reactive than the commonly examined aromatic amines (-NH2), and this allowed for the multi-step reactions to be carried out in tandem within the MOF. Preliminary findings indicate that the complexity thus achieved can affect reactions that were previously accomplished only in the presence of enzymes.
TL;DR: Characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorbate-adsorbate enthalPies of MOF-801 are nearly constant for a wide range of vapor uptakes.
Abstract: Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes.
TL;DR: This work presents a generalizable chemical strategy for making transparent glassy MOFs by assembly from viscous solutions of metal node and organic strut and subsequent evaporation of a plasticizer-modulator solvent and represents an important step forward in translating the versatility and porosity of MOFs to glassy materials.
Abstract: While glassy materials can be made from virtually every class of liquid (metallic, molecular, covalent, and ionic), to date, formation of glasses in which structural units impart porosity on the nanoscopic level remains undeveloped. In view of the well-established porosity of metal–organic frameworks (MOFs) and the flexibility of their design, we have sought to combine their formation principles with the general versatility of glassy materials. Although the preparation of glassy MOFs can be achieved by amorphization of crystalline frameworks, transparent glassy MOFs exhibiting permanent porosity accessible to gases are yet to be reported. Here, we present a generalizable chemical strategy for making such MOF glasses by assembly from viscous solutions of metal node and organic strut and subsequent evaporation of a plasticizer–modulator solvent. This process yields glasses with 300 m2/g internal surface area (obtained from N2 adsorption isotherms) and a 2 nm pore–pore separation. On a volumetric basis, this...
TL;DR: This study reports a robust and porous crystalline MOF, Zn3(PBSP)2 or MOF-910, constructed from a novel linker PBSP bearing three distinct types of coordinative functionality, and adopts a complex and previously unreported topology termed tto.
Abstract: Structural diversity of metal–organic frameworks (MOFs) has been largely limited to linkers with at most two different types of coordinating groups. MOFs constructed from linkers with three or more nonidentical coordinating groups have not been explored. Here, we report a robust and porous crystalline MOF, Zn3(PBSP)2 or MOF-910, constructed from a novel linker PBSP (phenylyne-1-benzoate, 3-benzosemiquinonate, 5-oxidopyridine) bearing three distinct types of coordinative functionality. The MOF adopts a complex and previously unreported topology termed tto. Our study suggests that simple, symmetric linkers are not a necessity for formation of crystalline extended structures and that new, more complex topologies are attainable with irregular, heterotopic linkers. This work illustrates two principles of reticular chemistry: first, selectivity for helical over straight rod secondary building units (SBUs) is achievable with polyheterotopic linkers, and second, the pitch of the resulting helical SBUs may be fine...
TL;DR: In this article, a review of strategies employed to access synergistic functionality at the interface of nanocrystalline MOFs and inorganic nanocrystals (NCs) is presented.
Abstract: Controlling the chemistry at the interface of nanocrystalline solids has been a challenge and an important goal to realize desired properties. Integrating two different types of materials has the potential to yield new functions resulting from cooperative effects between the two constituents. Metal–organic frameworks (MOFs) are unique in that they are constructed by linking inorganic units with organic linkers where the building units can be varied nearly at will. This flexibility has made MOFs ideal materials for the design of functional entities at interfaces and hence allowing control of properties. This review highlights the strategies employed to access synergistic functionality at the interface of nanocrystalline MOFs (nMOFs) and inorganic nanocrystals (NCs).
08 Aug 2016
TL;DR: Porosity in metal-organic compounds has been studied in this article, but none of these had been shown to have permanent porosity until metalorganic frameworks were reported in the 1990s.
Abstract: Inorganic zeolites [1], mesoporous silica [2], and porous carbon [3] are useful materials because of their permanent porosity imparted by their architectural stability in the absence of guest molecules. The chemical functionalization and structure control of these classes of porous materials have been long‐standing challenges. Indeed, the incorporation of organic functionality and transition metal ions within the structures of these porous materials remain objectives highly sought after. Inorganic and organic molecules when linked into extended structures provide vast opportunities for making porous metal–organic crystals by design and for translating molecular organic and inorganic functionality and reactivity into the solid state. Metal–organic compounds having crystal structures with open space have been known since Werner’s work on coordination complexes [4, 5]. Since that time many different classes of porous molecular crystals and extended solids have been studied, but none of these had been shown to have permanent porosity until metal–organic frameworks (MOFs) were reported in the 1990s [6–11]. This contribution highlights the structures and porous properties of important crystalline molecular complexes and extended structures dating from Werner compounds up to and including MOFs. Porosity in Metal–Organic Compounds
TL;DR: Water-soluble metal-organic complex array 1, bearing Ru(II), Pt(II) and Rh(III) complexes at the side residues of the short peptide, exhibits anion and pH-responsive self-assembly behaviours in aqueous media.
TL;DR: The key advance in this regard has been the development of strategies to overcome the "crystallization problem" which is usually encountered when attempting to link molecular building units into covalent solids.
Abstract: Linking molecular building units by covalent bonds to make crystalline extended structures has given rise to metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), thus bringing the precision and versatility of covalent chemistry beyond discrete molecules to extended structures. The key advance in this regard has been the development of strategies to overcome the “crystallization problem”, which is usually encountered when attempting to link molecular building units into covalent solids. Currently, numerous MOFs and COFs are made as crystalline materials in which the large size of the constituent units provides for open frameworks. The molecular units thus reticulated become part of a new environment where they have (a) lower degrees of freedom because they are fixed into position within the framework; (b) well-defined spatial arrangements where their properties are influenced by the intricacies of the pores; and (c) ordered patterns onto which functional groups can be covalently attached...
16 Jun 2016
Patent•
25 Nov 2016TL;DR: In this paper, the authors describe a covalent organic framework (COF) that is constructed from weaving a plurality of long organic threads together, where long organic strands are connected together in a woven pattern using organic ligands/complexes.
Abstract: The disclosure provides for covalent organic frameworks (COFs) that constructed from weaving a plurality of long organic threads together. In particular, the disclosure provides for the construction of woven COFS, where long organic strands are connected together in a woven pattern using organic ligands/complexes that when orientated in certain geometries are capable of reversibly binding metal ions.
TL;DR: Li et al. as discussed by the authors used a heterotritopic linker which leads to a stable, porous metal-organic framework (MOF-910) with a new network topology.
Abstract: Metal-organic frameworks (MOFs) are crystalline materials, composed of inorganic clusters or coordination spheres (secondary building units, SBUs), connected by organic linkers through strong bonds. Most of the linkers employed in MOF synthesis are highly symmetric, leading to structures with only a few network topologies, aiming for a high network transitivity.[1] A reason for this is that for linkers with identical functional groups, a pH exists that allows reversible bond formation to the metal centers, hence facilitating crystal growth. Here we report the use of a heterotritopic linker which leads to a stable, porous MOF (BET surface area 2140 m2g-1) with a new network topology (named tto). MOF-910 crystallizes in the trigonal spacegroup R-3c with lattice parameters a = 47.239(2) Å and c = 27.1216(12) Å. The structure (Figure 1) consists of hexagonal channels 28 Å in diameter constructed from infinite helical SBUs of Zn2+ ions ligated by the oxygen and nitrogen atoms of the linker, which bears a benzoate, a semiquinonate and a pyridonate functional group. The structure is achiral, as it contains an equal amount of leftand right-handed helical SBUs. The semiquinonate and the pyridonate group align together at the same SBU with the benzoate group bridging to the opposing SBU. The benzoate is disordered, showing two distinct conformations. Despite the differences of the pKa values of the functional groups (benzoate: 4.2; catecholate: 9.5; pyridonate: 11),[2,3] synthetic conditions could be derived which led to a homogeneous, stable product. These results show the potential of extending the variety of known MOFs constructed with new network topologies utilizing much higher complexity in the organic linker molecules than previously achieved. [1] M. Li, D. Li, M. O’Keeffe, O. M. Yaghi, Chem. Rev. 2014, 114, 1343. [2] E. P. Serjeant, B. Dempsey, Ionization Constants of Organic Acids in Aqueous Solution; Pergamon Press: Oxford, 1979. [3] J. A. Joule, K. Mills, Heterocyclic Chemistry, 5th ed.; John Wiley& Sons, Ltd.: West Sussex, U.K., 2010; pp 143. Figure 1. a) Heterotritopic linker. b) Section from helical SBU. c) Structure of MOF-910 viewed along the c-axis along the hexagonal channels. Color scheme: Zn, blue; C, black; O, red; N, green. Hydrogen atoms omitted for clarity.
TL;DR: The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.
Abstract: We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.
TL;DR: In this article, Covalent organic frameworks (COFs) are a new class of porous organic structures whose backbone is composed entirely of light elements (B, C, N, O, Si) that represent a successful demonstration of how crystalline materials of covalent solids can be achieved.
Abstract: Linking organic molecules by covalent bonds into extended solids typically generates amorphous, disordered materials. The ability to develop strategies for obtaining crystals of such solids is of interest because it opens the way for precise control of the geometry and functionality of the extended structure, and the stereochemical orientation of its constituents. Covalent organic frameworks (COFs) are a new class of porous covalent organic structures whose backbone is composed entirely of light elements (B, C, N, O, Si) that represent a successful demonstration of how crystalline materials of covalent solids can be achieved. COFs are made by combination of organic building units covalently linked into extended structures to make crystalline materials. The attainment of crystals is done by several techniques in which a balance is struck between the thermodynamic reversibility of the linking reactions and their kinetics. This success has led to the expansion of COF materials to include organic units linked by these strong covalent bonds: B-O, C-N, B-N, and B-O-Si. Since the organic constituents of COFs, when linked, do not undergo significant change in their overall geometry, it has been possible to predict the structures of the resulting COFs, and this advantage has facilitated their characterization using powder X-ray diffraction (PXRD) techniques. It has also allowed for the synthesis of COF structures by design and for their formation with the desired composition, pore size, and aperture. In practice, the modeled PXRD pattern for a given expected COF is compared with the experimental one, and depending on the quality of the match, this is used as a starting point for solving and then refining the crystal structure of the target COF. These characteristics make COFs an attractive class of new porous materials. Accordingly, they have been used as gas storage materials for energy applications, solid supports for catalysis, and optoelectronic devices. A large and growing library of linkers amenable to the synthesis of COFs is now available, and new COFs and topologies made by reticular synthesis are being reported. Much research is also directed toward the development of new methods of linking organic building units to generate other crystalline COFs. These efforts promise not only new COF chemistry and materials, but also the chance to extend the precision of molecular covalent chemistry to extended solids.