Hierarchically ordered homochiral metal-organic frameworks built from exceptionally large rectangles and squares

Hierarchically ordered homochiral metal-organic frameworks were built from the Cu(II) connecting point and the new (R)-6,6'-dichloro-2,2'-diethoxy-1,1'-binaphthyl-4,4'-bis(p-ethynylpyridine) bridging ligand (L). [Cu(3)L(4)(DMF)(6)(H(2)O)(3)(ClO(4))][ClO(4)](5).10DMF.10EtOH.7H(2)O (1) adopts a unique three-dimensional framework structure via simultaneous interlocking and interpenetration of one-dimensional ladders formed by linking rectangles of 24.8 x 48.6 A(2) in dimensions, whereas [Cu(3)L(5)(DMF)(8)][ClO(4)](6).6DMF.8EtOH.Et(2)O.6H(2)O (2) exhibits an interesting network topology by threading two-dimensional coordination square grids with one-dimensional coordination polymers.     

Construction of two 3D homochiral frameworks with 1D chiral pores via chiral recognition

The reactions of a pair of enantiomers of macrocyclic nickel(II) complexes with racemic penicillamine generated two 3D hydrogen-bonded homochiral frameworks of {[Ni(f-(SS)-L)](2)(l-pends)(ClO(4))(2)}(n) (Λ-1) and {[Ni(f-(RR)-L)](2)(d-pends) (ClO(4))(2)}(n) (Δ-1). The frameworks possess 1D tubular pores and opposite right/left-handed helical porous surfaces (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; pends(2-) = penicillaminedisulfide anion).     

Homochiral 3D metal-organic frameworks from chiral 1D rods: 6-way helical packing

The chiral 3D MOFs resulted from the packing of chiral 1D SBBs were studied. It was demonstrated that the final packing pattern is sensitively dependent on the dimension of SBBs. In addition, we were able to identify a new plywood-like network from ligand 2H(2) exhibiting an unprecedented six-way chiral helical packing motif, which extends the list of invariant rod packings.     

Two luminescent enantiomorphic 3D metal-organic frameworks with 3D homochiral double helices

Two enantiomorphic Cd(II) coordination polymers with three-dimensional homochiral double helices have been assembled respectively from two tripodal enantiopure amino acid derivatives, which exhibit (3,4)-connected (6(3))(6(3).10(3)) topology and strong purple fluorescence.     

A homochiral triple helix constructed from an axially chiral bipyridine

A homochiral triple helix was self-assembled from an axially chiral bipyridine and a linear metal-connecting point, which further assembles into a 2D network via infinite pi...pi stacking interactions and acts as a host for the inclusion of guest molecules.     

3D metal-organic frameworks based on elongated tetracarboxylate building blocks for hydrogen storage

Two 3D metal-organic frameworks (MOFs) with a new biphenol-derived tetracarboxylate linker and Cu(II) and Zn(II) metal-connecting points were synthesized and characterized by single-crystal X-ray crystallographic studies. The two isostructural MOFs exhibit distorted PtS network topology and show markedly different framework stability. The porosity and hydrogen uptake of the frameworks were determined by gas adsorption experiments.     

2D conductive metal-organic frameworks for electronics and spintronics

Two-dimensional(2D) materials showcase great potentials in both fundamental research and technology development, thanks to their unique chemical and physical properties that are usually not available in corresponding bulk counterparts. As an emerging class of 2D materials, 2D conductive metal-organic frameworks(2D c-MOFs) exhibit the characteristics of pre-designable and tunable structures, excellent crystallinity, intrinsic porosity and superior conductivity. During the past decade, 2D c-MOFs have been rapidly developed in electronics, sensors, energy storage devices, etc. In this review, the electrical, magnetic and quantum properties of 2D c-MOFs are surveyed in detail. Their applications in semiconductor, metal, superconductor, topological insulator and porous magnet are highlighted. We envision that the combination of 2D c-MOFs with quantum materials could evoke rich physics, flexible chemistry and potential applications in both electronics and spintronics.     

A pair of 3D homochiral metal-organic frameworks: spontaneous resolution, single-crystal-to-single-crystal transformation and selective adsorption properties

A novel achiral hexacarboxylic ligand L was synthesized. Spontaneous resolution occurred during the reaction of L with Eu(NO(3))(3) to produce a pair of enantiomers of 1a and 1b with a formula of [EuL(NO(3))(3)(H(2)O)]·13H(2)O, which possesses 1D chiral open channels formed by triple-stranded helical chains. When heated to 60 °C, 1a releases coordinated and partial lattice H(2)O molecules to give a complex of [EuL(NO(3))(3)]·4H(2)O (1a'), accompanied by a single-crystal-to-single-crystal transformation from 1a to 1a', with the space group changing from P2(1) to P3(1)2. The dehydrated 1 can selectively adsorb water over organic solvents and exhibits reversible water adsorption upon dehydration and hydration.     

Chemoenzymatic synthesis of chiral 4,4'-bipyridyls and their metal-organic frameworks

The first enantiopure 4,4'-bipyridyls, , , and have been prepared in four or five steps via bacterial dioxygenase-catalysed cis-dihydroxylation of 4-chloroquinoline and C-C coupling; ligands and are found to be effective building blocks for the preparation of chiral metal-organic frameworks as demonstrated with the rational synthesis of two pillared-grid structures [Zn(2)(fumarate)(2)(L)], which exhibit interesting structural and dynamic aspects.     

Construction of robust open metal-organic frameworks with chiral channels and permanent porosity

Four new metal-organic frameworks (MOFs) containing chiral channels have been synthesized using an achiral, triazine-based trigonal-planar ligand, 4,4',4' '-s-triazine-2,4,6-triyltribenzoate (TATB), and an hourglass secondary building unit (SBU): Zn3(TATB)2(H2O)2.4DMF.6H2O (1); Cd3(TATB)2(H2O)2.7DMA.10H2O (2); [H2N(CH3)2][Zn3(TATB)2(HCOO)].HN(CH3)2.3DMF.3H2O (3); [H2N(CH3)2][Cd3(TATB)2(CH3COO)].HN(CH3)2.3DMA.4H2O (4). MOFs 1 and 2 are isostructural and possess (10,3)-a nets containing large chiral channels of 20.93 and 21.23 A, respectively, but are thermally unstable due to the easy removal of coordinated water molecules on the SBU. Replacement of these water molecules by formate or acetate generated in situ leads to 3 and 4, respectively. Formate or acetate links SBUs to form infinite helical chains bridged by TATB to create three-dimensional anionic networks, in which one of the two oxygen atoms of the formate or acetate is uncoordinated and points into the void of the channels. This novel SBU-stabilization and channel-functionalization strategy may have general implications in the preparation of new MOFs. Thermogravimetric analysis (TGA) shows that solvent-free 3' is thermally stable to 410 degrees C, while TGA studies on samples vapor-diffused with water, methanol, and chloroform show reversible adsorption. MOF 3 also has permanent porosity with a large Langmuir surface area of 1558 m2/g. All complexes exhibit similar strong luminescence with a lambdamax of approximately 423 nm upon excitation at 268.5 nm.     

Puckered-boat conformation hexameric water clusters stabilized in a 2D metal-organic framework structure built from CuII and 1,2,4,5-benzenetetracarboxylic acid

1,2,4,5-Benzenetetracarboxylic acid (btcH(4)) reacts with Cu(NO(3))(2).6H(2)O to form 2D coordination polymeric structure [[Cu(2)(btc)(Py)(4).2H(2)O].4H(2)O](n), 1, in the presence of pyridine from water at room temperature. Puckered-boat-shaped hexameric water clusters resulting from four free water molecules and two water molecules coordinating to metal ions join these sheets to make a 3D network. These water clusters behave as pillars to join those sheets which is the key factor stabilizing the 3D network. Thermal analysis, X-ray powder diffraction, and X-ray structure analysis have been used to characterize this compound. Crystal data for 1 follow: triclinic space group P1, a = 8.905(3) A, b = 11.137(4) A, c = 17.484(2) A, alpha = 82.342(6) degrees, beta = 81.312(3) degrees, gamma = 82.361(4) degrees V= 1687.5(1)A(3), Z = 2, R1 = 0.0331, wR2 = 0.0886, S =1.066.     

Temperature-controlled chiral and achiral copper tetrazolate metal-organic frameworks: syntheses, structures, and I2 adsorption

Four tetrazole-based three-dimensional (3D) metal-organic frameworks (MOFs), {[Cu(II)(btz)]·0.5H(2)O}(n) (1), [Cu(II)(btz)](n) (1'), {[Cu(II)(btz)]·0.5I(2)}(n) (1'·0.5I(2)), and [Cu(II)Cu(I)(2)(btz)(2)](n) (2) [H(2)btz = 1,5-bis(5-tetrazolo)-3-oxapentane)], have been successfully obtained and characterized by crystallography. Compound 1 features a chiral porous framework. The bulk crystallization of 1 is composed of enantiomers 1a (P4(1)) and 1b (P4(3)), which has been demonstrated by the crystal structure analyses of nine crystals of 1 randomly selected. The Cotton effect displayed in the solid-state circular dichroism spectrum of 1 is therefore attributed to enantiomeric excess rather than enantiopurity. The completely dehydrated phase of 1, that is, 1', can adsorb 0.5 I(2) molecule per formula unit to yield compound 1'·0.5I(2), which has been supported by single-crystal X-ray diffraction, elemental analysis, and thermogravimetric analysis. The locations of I(2) in the pores were unambiguously determined, and the interactions between I(2) molecules and the pore structures were investigated. Compound 2 crystallizes in an achiral C2/c space group. Interestingly, the formations of chiral 1 and achiral 2 significantly depend on the reaction temperature. Between 80 and 140 °C, we got compound 1 as the only product. At 150 °C, both 1 and 2 were in coexistence in the final product. From 160 to 180 °C, only compound 2 was obtained. More interestingly, treatment of the crystals of 1 or the mixture of 1 and 2 obtained at 150 °C in their mother liquor at 170 °C yielded the crystals of 2 in a single phase.     

Structure, luminescence, and adsorption properties of two chiral microporous metal-organic frameworks

Two 3D chiral multifunctional microporous MOFs, Zn3(BTC)2(DMF)3(H2O).(DMF)(H2O) (1) and Cd(4)(BTC)3(DMF)2(H2O)2.6(H2O) (2) (H(3)BTC = 1,3,5-benzenetricarboxylic acid and DMF = N,N'-dimethylformamide), have been synthesized in the presence of organic bases tributylamine (TBA) and triethylamine (TEA), respectively. 1 (C(30)H(38)N(4)O(18)Zn(3)) crystallizes in the tetragonal P4(1)2(1)2 space group (a = 13.6929(19) A, c = 50.664(10) A, V = 9499(3) A(3), and Z = 8). 2 (C33H39N2O28Cd4) crystallizes in the tetragonal P4(3)22 space group (a = 10.3503(4) A, c = 52.557(3) A, V = 5630.4(4) A(3), and Z = 4). X-ray crystallography reveals that 1 consists of a 3D open framework with the (6(3))(4)(6(2).8(2).10(2))(6.(4)8(2))(2) topology, but 2 exhibits a 3D open network with the (4(2).5)(2)(4.(4)5.(10)6.(8)7.(4)8(2)) topology. The solid-state excitation-emission spectra show that the strongest excitation peaks for 1 and 2 are at 341 and 319 nm, and their emission spectra mainly show strong peaks at 410 and 405 nm, respectively. The amounts adsorbed of 1 (2) are 169 mg/g (126 mg/g) for H2O, 137 mg/g (102 mg/g) for C2H5OH, and 133 mg/g (99 mg/g) for CH3OH, which are equivalent to the adsorption of about 62 (34) H2O, 20 (11) C2H5OH, and 28 (16) CH3OH per unit cell, respectively.     

Three-component reactions leading to 2D and 3D metal-organic frameworks assembled on dinickel-carboxylate secondary building units

Three-component reactions involving Ni(II) ions and dicarboxylate and bipyridyl ligands under hydrothermal conditions produce two novel metal-organic coordination polymers formulated empirically as [Ni(PDA)(BPE)] (1) and [Ni₂(PDA)₂(BPP)(H₂O)]·2.5H₂O (2), where PDA = 1,4-phenylenediacetate, BPE = 1,2-bis(4-pyridyl)ethane, and BPP = 1,3-bis(4-pyridyl)propane. Both compounds possess 2D or 3D metal-organic frameworks (MOFs) that are assembled on dinickel-carboxylate secondary building units. Compound 1 has a condensed 3D MOF, whereas 2 contains void between 2D MOFs where guest water molecules reside. Both compounds demonstrate antiferromagnetic coupling between Ni(II) ions.     

Construction of open metal-organic frameworks based on predesigned carboxylate isomers: from achiral to chiral nets

The four-connected carboxylate ligand N,N,N',N'-tetrakis(4-carboxyphenyl)-1,4-phenylenediamine (TCPPDA) exists as three stereoisomers: a pair of enantiomers (deltaD2- and lambdaD2-TCPPDA) and a diastereomer (C2h-TCPPDA). TCPPDA was predesigned for the construction of isomeric coordination networks. Reactions of M(NO3)2 (M=Cu, Zn, Co) or Nd(NO)3 with TCPPDA under solvothermal conditions gave rise to five novel porous metal-organic frameworks: [Cu2(D2-tcppda)(H2O)2].2 DMSO.6H2O (1), [Cu2(C2h-tcppda)(H2O)2].2DMSO.6H2O (2), [Co3(D2-Htcppda)2].4DEF.5H2O (3), [Nd2(D2-tcppda)(C2h-tcppda)0.5(DMSO)3]3 DMSO5 H2O (4), and [Zn4O(D2-tcppda)1.5].DMF.H2O (5) (DMSO=dimethyl sulfoxide, DEF=diethylformamide, DMF=dimethylformamide). Complexes 1 and 2 are supramolecular isomers, in which all the ligands adopt pseudotetrahedral (both deltaD2- and lambdaD2-TCPPDA) and rectangular (C2h-TCPPDA) geometries, respectively. Both compounds connect paddlewheel secondary building units (SBUs) to form three-dimensional porous networks possessing PtS and NbO nets, respectively. In 3, all ligands possess pseudotetrahedral (both deltaD2- and lambdaD2-TCPPDA) geometry and link hourglass SBUs to form a three-dimensional porous framework. Compound 4 contains all three stereoisomers (C2-, deltaD2-, and lambdaD2-TCPPDA), thus, has both pseudotetrahedral and rectangular geometries. D2-TCPPDA connects the binuclear neodymium units to generate a two-dimensional layer, further linked by C2h-TCPPDA to create a three-dimensional open framework. In 5, all the ligands possess pseudotetrahedral geometry (D2-TCPPDA), as found in 1 and 3. However, all the TCPPDA ligands in 5 appear as either the deltaD2 or the lambdaD2 form, thus, the whole structure is homochiral. Complex 5 crystallizes in the I4(1)32 space group and the octahedral SBU in 5 is connected by the enantiopure TCPPDA to generate a three-dimensional porous network possessing the corundum Al2O3 net. Complexes 1, 2, and 5 possess permanent porosity, and 4 and 5 exhibit strong luminescence at lambdamax=423 and 424 nm, respectively, upon excitation at 268.5 nm.     

Three novel isomeric zinc metal-organic frameworks from a tetracarboxylate linker

Three porous supramolecular isomers (IZE-1, IZE-2, and IZE-3) with the same framework component [Zn(2)(EBTC)(H(2)O)(2)] (EBTC = 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylate) were successfully constructed by finely tuning the reaction condition. Although both IZE-1 and IZE-2 are constructed from the linear EBTC subunits and one kind of regular [Zn(2)(CO(2))(4)] paddlewheels, their frameworks exhibit two different (3,4)-c net of fof (sqc1575) and sqc1572, respectively, resulting in cavities with different size and shape. However, as for isomer IZE-3, the EBTC ligands are bent and one-half of the [Zn(2)(CO(2))(4)] paddlewheels are distorted, leading to a novel (3,4,4)-c hyx net with point symbol (6.7(2))(4)(6(2).8(2).10(2))(7(2).8(2).11(2)) and vertex symbol (6.7.7)(4)(7(2).7(2).8.8.12.12)(6.6.8.8.10(2).10(2)). Quantum chemical calculations by DFT indicate that the three isomers have very close thermodynamic stabilities, which may explain that subtle condition change leads to variation of the frameworks. Further theoretical semiempirical investigation on the interactions between solvent molecules and compounds shows different hydrogen binding patterns in good agreement with the experimental observations. Furthermore, they exhibit good solid-state luminescence properties with long lifetime.     

Separation of CO2 from CH4 using mixed-ligand metal-organic frameworks

The adsorption of CO2 and CH4 in a mixed-ligand metal-organic framework (MOF) Zn 2(NDC) 2(DPNI) [NDC = 2,6-naphthalenedicarboxylate, DPNI = N, N'-di-(4-pyridyl)-1,4,5,8-naphthalene tetracarboxydiimide] was investigated using volumetric adsorption measurements and grand canonical Monte Carlo (GCMC) simulations. The MOF was synthesized by two routes: first at 80 degrees C for two days with conventional heating, and second at 120 degrees C for 1 h using microwave heating. The two as-synthesized samples exhibit very similar powder X-ray diffraction patterns, but the evacuated samples show differences in nitrogen uptake. From the single-component CO2 and CH4 isotherms, mixture adsorption was predicted using the ideal adsorbed solution theory (IAST). The microwave sample shows a selectivity of approximately 30 for CO2 over CH4, which is among the highest selectivities reported for this separation. The applicability of IAST to this system was demonstrated by performing GCMC simulations for both single-component and mixture adsorption.     

One dense and two open chiral metal-organic frameworks: crystal structures and physical properties

Three 3D robust homochiral helical coordination polymers, [Cu(2,2',3,3'-H2odpa)(bpy)] (1), {[Ni4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)16} (2), and {[Co4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)14} (3), have been hydrothermally synthesized from a flexible ligand of 2,2',3,3'-odpda (2,2',3,3'-oxydiphthalic dianhydride). Compound 1 crystallized in space group P3(1)21 and has a rare chiral dense qzd 7.(5)9 topology that incorporates single helical substructures with the same accessibility, whereas compounds 2 and 3 crystallized in the space group C2 and possessed isostructural 3D chiral open frameworks based on the homochiral 2D sheets and 4,4'-bpy pillars. TGA and PXRD analyses show that the porous framework of 2 is stable after the removal of solvent water molecules. In contrast, 3 changed its structure to an amorphous one because of the simultaneous loss of solvent and coordination water molecules. 1 is nearly paramagnetic, whereas weak ferromagnetic interactions between M(II) (M = Ni, Co) ions have been found in 2 and 3.