Abstract
Curvy ligands for H
2
storage?
Enhancement of H
2
adsorption has been observed in coordination framework materials, an example of which is depicted, by the introduction of phenanthrene and ...9,10‐dihydrophenanthrene groups into porous Cu
II
–carboxylate framework materials of NbO topology.
magnified image
Solvothermal reaction of the ligands H
4
L
110
((2,7‐phenanthrenediyl)diisophthalic acid) and H
4
L
111
(2,7‐(9,10‐dihydrophenanthrenediyl)diisophthalic acid) with Cu(NO
3
)
2
⋅
2.5 H
2
O in a slightly acidified mixture of DMF/1,4‐dioxane/H
2
O afforded the solvated framework compounds Cu
2
(L
110
)(H
2
O)
2
(DMF)
7.5
(H
2
O)
5
(NOTT‐110) and Cu
2
(L
111
)(H
2
O)
2
(DMF)
7.5
(H
2
O)
5
(NOTT‐111), respectively. Crystal structure determinations confirmed that NOTT‐110 and NOTT‐111 have the same NbO framework structure, differing only at the 9 and 10 positions of the phenanthrene group. The BET surface areas for desolvated NOTT‐110 and NOTT‐111 were estimated to be 2960 and 2930 m
2
g
−1
, respectively. Compared with their phenyl analogues, introduction of phenanthrene groups to these porous Cu
II
–carboxylate framework materials leads to an enhancement of H
2
adsorption. Thus, the H
2
isotherms for desolvated NOTT‐110 and NOTT‐111 confirm 2.64 and 2.56 wt % total H
2
uptake, respectively, at 1 bar and 78 K. NOTT‐110 shows a high total H
2
storage capacity of 7.62 wt % at 55 bar and 77 K (8.5 wt % at saturation) with a total volumetric capacity of 46.8 g
L
−1
at 55 bar and 77 K.
The thermodynamic stabilities (Δ
ri
G) of various ceramics towards Pb
Li alloys have been evaluated as a function of temperature, lithium composition and, for lithium, non-metal solute concentration. ...For non-metal saturated alloys, both increasing temperature and decreasing lithium composition (from lithium to Pb
-17Li) lead to increased stability (more positive Δ
r
G values). Reducing non-metal solute concentration in lithium by cold trapping leads to decreased stability. Of the ceramics presently being assessed as coating materials, AlN, TiN, TiC, Y
2O
3 and CaO are stable in reactor grade Pb
17Li and reactor grade lithium, β-SiC, Al
2O
3, SiO
2 and MgO are stable in Pb
17Li but not lithium and Cr
2O
3 is unstable in both breeders.
Reaction of 4,4′-bipyridine-N,N′-dioxide (L) with a variety of transition-metal salts in MeOH affords a range of coordination polymer products. For the complexes FeCl3(μ-L)∞, 1, and ...(Cu(L)2(OHMe)2(μ-L)·2PF6·n(solv))∞, 2, 1D chain structures are observed, whereas (Mn(μ-L)3·2ClO4)∞, 3, and (Cu(μ-L)3·2BF4)∞, 4, both show 2D sheet architectures incorporating an unusual 36-hxl topology. The more common 44-sql topology is observed in Cd(ONO2)2(μ-L)2∞, 5, (Cu(OHMe)2(μ-L)2·2ZrF5)∞, 6, (Cu(L)2(μ-L)2·2EF6)∞ (7 E = P; 8 E = Sb), and (Et4NCu(OHMe)0.5(μ-L)2(μ-FSiF4F)0.5·2SbF6·n(solv))∞, 9. In 6, the ZrF5− anion, formed in situ from ZrF62−, forms 1D anionic chains (ZrF5−)∞ of vertex-linked octahedra, and these chains thread through a pair of inclined polycatenated (Cu(OHMe)2(μ-L)22+)∞ 44-sql grids to give a rare example of a triply intertwined coordination polymer. 9 also shows a 3D matrix structure with 44-sql sheets of stoichiometry (Cu(L)22+)∞ coordinatively linked by bridging SiF62− anions to give a structure of 5-c 44.66-sqp topology. The mononuclear Cu(L)6·2BF4 (10) and Cd(L)6·2NO3 (11) and binuclear complexes (Cu(L)(OH2))2(μ-L)2)·2SiF6·n(solv), 12, are also reported. The majority of the coordination polymers are free of solvent and are nonporous. Thermal treatment of materials that do contain solvent results in structural disintegration of the complex structures giving no permanent porosity.
A robust 3-D porous structure of formula Ln2(PDC)3(DMF)2∞ has been constructed from lanthanide cations (Ln = Er3+ or Y3+) and the non-linear anionic bridging ligand, pyridine-3,5-dicarboxylate ...(PDC2-) in dimethylformamide (DMF). The solvated framework polymers {M2(PDC)3(DMF)2·n(solv)}∞ (M = Er, Y) undergo a solid-state, crystal-to-crystal reaction upon heating and are converted via loss of both sorbed and coordinated solvent and rearrangement of the framework core to give a desolvated and porous form with retention of structural integrity. This structural transfer is the first crystallographically characterized system with lanthanide metal ions. These porous products are shown to be effective absorbants for H2, N2, and benzene.
Reaction of ScX3 (X=NO3−, CF3SO3−, ClO4−) with 4,4′‐bipyridine‐N,N′‐dioxide (L) affords topologically distinct six‐connected three‐dimensional coordination frameworks, {Sc(L)3(NO3)3}∞ (1), ...{Sc(L)3(CF3SO3)3(CH3OH)2.7(H2O)3}∞ (2), {Sc(L)3(ClO4)3}∞ (3) and {Sc(L)4(H2O)2(ClO4)3}∞ (4). Compounds 1, 2 and 3 are networks based on octahedrally co‐ordinated ScO6 centres bound through six oxygen atoms from six separate N‐oxide ligands L. Compounds 1 and 3 are doubly interpenetrated and have α‐polonium‐type structures of 41263 topology based upon three intersecting (4,4) nets. The structure of 2 is unusual and shows parallel, co‐planar layers of (4,4) nets connected in a criss‐crossed fashion to afford a new 48668 topology. In 4 only four ligands L bind to each ScIII centre with two additional water molecules bridging metal nodes. Significantly, the bridges formed by L do not sit in a plane and if connections through L are considered alone the resultant structure is a diamondoid array typically based upon a tetrahedral connecting node at Sc. Five interpenetrating diamondoid networks are observed that are cross‐bridged by water molecules to form a single three‐dimensional array of 4867 topology. Compound 4 can also be viewed as incorporating two intersecting (4,4) grids based upon two ligands L and two bridging waters. Thus, variation of anion, solvent and conditions critically affects the structures of products formed, and the series of polymers reported herein illustrates how tectons based upon (4,4) grids can be combined and distorted to form non‐NaCl topologies and even cross‐bridged, multiply interpenetrated diamondoid materials. Both compounds 2 and 4 represent unusual examples of self‐penetrated coordination frameworks.
ScIII nodes with 4,4′‐bipyridine‐N,N′‐dioxide afford either doubly‐interpenetrated α‐polonium‐type structures of 41263 topology as in NaCl (see picture, left), or alternatively non‐NaCl structures incorporating either criss‐crossed connected co‐planar layers of (4,4) nets in a 48668 topology, or a diamondoid array based upon a tetrahedral node (see picture, right). In the latter, bridging water molecules bridge the five interpenetrated diamondoid frameworks into a single self‐penetrating three‐dimensional array of 4867 topology.
A family of Cu(II)-based metal-organic frameworks (MOFs) has been synthesized using three pyridyl-isophthalate ligands, H₂L¹ (4′-(pyridin-4-yl)biphenyl-3,5-dicarboxylic acid), H₂L² ...(4″-(pyridin-4-yl)-1,1′: 4′,1″-terphenyl-3,5-dicarboxylic acid) and H₂L³ (5-4-(pyridin-4-yl)naphthalen-1-ylbenzene-1,3-dicarboxylic acid). Although in each case the pyridyl-isophthalate ligands adopt the same pseudo-octahedral Cu₂(O₂CR)₄N₂ paddlewheel coordination modes, the resulting frameworks are structurally diverse, particularly in the case of the complex of Cu(II) with H₂L³, which leads to three distinct supramolecular isomers, each derived from Kagomé and square nets. In contrast to Cu(L²) and the isomers of Cu(L³), Cu(L¹) exhibits permanent porosity. Thus, the gas adsorption properties of Cu(L¹) were investigated with N₂, CO₂ and H₂, and the material exhibits an isosteric heat of adsorption competitive with leading MOF sorbents for CO₂. Cu(L¹) displays high H₂ adsorption, with the density in the pores approaching that of liquid H₂. This article is part of the themed issue 'Coordination polymers and metal—organic frameworks: materials by design'.
A family of Cu(II)-based metal-organic frameworks (MOFs) has been synthesized using three pyridyl-isophthalate ligands, H2L1 (4′-(pyridin-4-yl)biphenyl-3,5-dicarboxylic acid), H2L2 ...(4′′-(pyridin-4-yl)-1,1′:4′,1′′-terphenyl-3,5-dicarboxylic acid) and H2L3 (5-4-(pyridin-4-yl)naphthalen-1-ylbenzene-1,3-dicarboxylic acid). Although in each case the pyridyl-isophthalate ligands adopt the same pseudo-octahedral Cu2(O2CR)4N2 paddlewheel coordination modes, the resulting frameworks are structurally diverse, particularly in the case of the complex of Cu(II) with H2L3, which leads to three distinct supramolecular isomers, each derived from Kagomé and square nets. In contrast to Cu(L2) and the isomers of Cu(L3), Cu(L1) exhibits permanent porosity. Thus, the gas adsorption properties of Cu(L1) were investigated with N2, CO2 and H2, and the material exhibits an isosteric heat of adsorption competitive with leading MOF sorbents for CO2. Cu(L1) displays high H2 adsorption, with the density in the pores approaching that of liquid H2.
This article is part of the themed issue ‘Coordination polymers and metal–organic frameworks: materials by design’.
Significant successes have been made over recent years in preparing co-ordination framework polymers that show macroscopic material properties, but in the vast majority of cases this has been ...achieved with
d-block metal-based systems. Lanthanide co-ordination frameworks also offer attractive properties in terms of their potential applications as luminescent, non-linear optical and porous materials. However, lanthanide-based systems have been far less studied to date than their
d-block counterparts. One possible reason for this is that the co-ordination spheres of lanthanide cations are more difficult to control and, in the absence of design strategies for lanthanide co-ordination frameworks, it is significantly more difficult to target materials with specific properties. However, this article highlights some of the exciting possibilities that have emerged from the earliest investigations in this field with new topological families of compounds being discovered from relatively simple framework components, including unusual eight, seven and five-connected framework systems. Our own research, as well as others, is leading to a much greater appreciation of the factors that control framework formation and the resultant observed topologies of these polymers. As this understanding develops targeting particular framework types will become more straightforward and the development of designed polyfunctional materials more accessible. Thus, it can be seen that lanthanide co-ordination frameworks have the potential to open up previously unexplored directions for materials chemistry. This article focuses on the underlying concepts for the construction of these enticing and potentially highly important materials.
Lanthanide co-ordination frameworks provide unique and enticing structural features and have the potential to open up previously unexplored directions for materials chemistry.
Coordination framework polymers derived from lanthanide metal ions with N,N ‘-dioxide ligands (4,4‘-bipyridine-N,N‘-dioxide, pyrazine-N,N‘-dioxide, 1,2-bis(pyridin-4-yl)ethane-N,N‘-dioxide, ...trans-1,2-bis(pyridin-4-yl)ethene-N,N‘-dioxide) exhibit such intricate architectures that a new strategy is required to appreciate and understand their structures. Rather than analyzing the overall structure in terms of the connectivity of individual metal nodes, which can lead in some cases to extremely complex topological treatments, our new strategy is based on the visualization of the structures as combinations of interconnected layered 2-D sheets or subnet tectons. Despite the diversity and relative complexities of many of the structures discussed here, they can all be described by the interconnection of just two types of 2-D subnet tectons, 44 square grids or 63 hexagonal grids. The interconnection of these layered sheets with bridging N,N ‘-dioxide molecules gives rise to both 2-D bilayer and 3-D network extended structures depending upon the relative dispositions of the interconnecting N,N ‘-dioxide ligands. Thus, 2-D bilayers result when the N,N ‘-dioxide ligands that bridge two subnet tectons are located on the same side of the sheet, while 3-D networks are formed when the bridging N,N ‘-dioxide ligands are located on both sides of the sheet. This analysis allows ready identification and interpretation of some of the most highly connected and complex architectures yet observed in materials chemistry.
New ternary and quaternary nitride halides, Ba2N(X,X′) (X = F, Cl, Br; X′ = Br, I), have been synthesized from the high temperature reactions of barium subnitride with the respective barium halides ...under an inert atmosphere. The former include the first fully characterized barium nitride halides for X other than F, and the latter are the first examples of barium nitride mixed halides. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques. The heavier ternary and quaternary nitride halides (X, X′ = Cl, Br, I) crystallize in the hexagonal space group R3̅m, with the anti-α-NaFeO2 structure. Ba2NF forms with both an anti-α-NaFeO2 structure, in which N3– and F– are ordered and an anion-disordered simple rock salt structure. The hexagonal polymorph of Ba2NF is the only example to date of a nitride fluoride adopting this layered structure. Both the ternary and the quaternary compounds display very weak, temperature independent paramagnetism.
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