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The excessive use of fossil energy has caused the CO2 concentration in the atmosphere to increase year by year. MOFs are ideal CO2 adsorbents that can be used in CO2 capture due to their excellent characteristics. Studies of the structure-activity relationship between the small structural differences in MOFs and the CO2 adsorption capacities are helpful for the development of efficient MOF-based CO2 adsorbents. Therefore, a series of pillar-layered MOFs with similar structural and different functional groups were designed and synthesized. The CO2 adsorption tests were carried out at 273 K to explore the relationship between the small structural differences in MOFs caused by different functional groups and the CO2 adsorption capacities. Significantly, compound 6 which contains a pyridazinyl group has a 30.9% increase in CO2 adsorption capacity compared to compound 1 with no functionalized group.

Three coordination polymers (CPs) were synthesized by using CdII, fluorescent 9,10-di(4-pyridyl)anthracene (dpa), and cyclohexane-1,4-dicarboxylic acid (H2cda), and they are [Cd2(dpa)2(cda)Cl2]n (1), [Cd(dpa)2(cda)]n (2) and [Cd(dpa)(cda)(H2O)]n (3). Both 1 and 2 are fluorescent and contain nonporous layers. 3 is an isomer of 2 and contains a porous diamondoid network. Fluorescent mixed matrix membranes were prepared by dispersing the particles of 1 or 2 within the matrix of polymethyl methacrylate, and showed high sensitivity and selectivity for detecting Cr2O72- in water. Both stability and recyclability of the MMMs were remarkably higher than those of the CP powders.

In this work, inspired by a water-assisted three-dimensional supramolecular structure 1, we use a mixed-ligand strategy to form a 3D pillared-layered matrix by the introduction of linear ligands to compete against the water molecules. The resulting analogue microporous MOFs of 2-H, 2-F and 2-N, decorated with different functional groups, similarly show the CO2 uptake. Thanks to the negligible N2 adsorption capacity, enhanced selective adsorption towards CO2 is achieved in compound 2-N. That is, we present here an alternative plan for the high CO2 selective adsorption performance. In addition, the structure stability and moderate affinity for CO2 of these microporous MOFs endow them with excellent reusability.

Metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) with tunable pore sizes, shapes and functionalities have excellent prospects in many applications, such as carbon capture. Molecular sieving can usually enable very high CO 2 adsorption selectivity but has rarely been achieved, because it is difficult to precisely control the pore size in the range of 3-4 Å. We report here three MOF isomers built from Cd II , terephthalic acid and 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine with the same stoichiometric ratio, among which 1 and 2 are framework-catenation isomers and 2 and 3 are framework-topological isomers. 1 contains 2-fold interpenetrated networks (topology of pcu) and 1D ultra-micropores and shows highly selective adsorption of CO 2 over N 2 and CH 4 , which is mainly ascribed to the molecular sieving effect of the framework. 2 contains a pcu network with 3D interconnected micropores, and 3 contains a kag network with much larger pores of 15 Å. Framework isomerization, in this case, was shown to be a feasible way of tuning the pore size of a MOF for selective CO 2 adsorption. The effects of hydrothermal reaction conditions and additives on the structures and the formation of the MOF isomers were also studied.

Tetrazole-based molecules have numerous bridging coordination modes which afford great synthetic possibilities for the preparation of porous metal-tetrazolate architectures for many applications, such as carbon capture. We reported here three tetrazole-based MOFs: 1, {[Cu 12 (ttz) 8/3 Cl 5 (H 2 O) 16 ] 11+ ·11Cl - } n (H 3 ttz = N 2 ,N 4 ,N 6 -tris(4-(1H-tetrazol-5-yl)phenyl)-1,3,5-triazine-2,4,6-triamine), contains highly positively charged Cu 12 clusters and the largest mesopores (32 Å) among the reported MOFs based on a tri-topic tetrazole ligand. 2 and 3 are two MOF isomers built by using Cu II and 2-(1H-tetrazol-5-yl)pyrimidine. 3 contains nonporous layers, while 2 contains 1D channels and showed high selectivity for adsorbing CO 2 , which should be attributed to the high density of free nucleophilic tetrazole N atoms on the pore surfaces. We found that the isomerization between 2 and 3 was caused by the diverse coordination modes of tetrazole-based ligands and can be controlled in synthesis processes.

Metal-organic frameworks (MOFs) are an exciting class of porous crystallized materials, which have attracted great interest in sustainable energy and environmental remediation. Magnetite (Fe3O4) is one of the best-known magnetic materials and has been extensively studied with respect to properties involving high saturation magnetization, biocompatibility and low toxicity. The combination of MOFs and Fe3O4 has shown its potential applications in drug delivery, catalysis and wastewater treatment. However, only classical porous MOFs are used to encapsulate magnetic nanoparticles, such as MIL-100(Fe), ZIF-8, UiO-66 and so on. Herein, we firstly synthesized a new MOF ZTB-1 and surveyed its applications in magnetic materials. As a result, a highly water-stable MOF-based magnetic material Fe3O4@ZTB-1 has been obtained, and it was for the first time used as an excellent adsorbent for the fast adsorption of Congo red (CR) from aqueous solutions, exhibiting an adsorption capacity of 458 mg CR per gram. The electrostatic interactions and hydrogen bond are responsible for binding of CR with Fe3O4@ZTB-1. The magnetic material Fe3O4@ZTB-1 shows a potential application in dyeing wastewater treatment.

A novel luminescent cobalt-organic framework was assembled and employed as a chemosensor for the detection of metal ions via fluorescence enhancement and quenching. The sensing mechanism was based on the exposed pyridyl and carboxyl functional sites in the MOF structure, which interacted with metal ions via Lewis acid-base interactions and electrostatic interactions.

Two metal-organic frameworks (MOFs), [Zn(BIPA)(tfbdc)]n (1) and {[Cd(BIPA)(tfbdc)(H2O)]·DMF}n (2), were hydrothermally synthesized using the self-assembly of the "V-shape" BIPA ligand (bis(4-(1H-imidazol-1-yl)phenyl)amine) and the H2tfbdc ligand (2,3,5,6-tetrafluorobenzene-1,4-dicarboxylic acid) with Zn/Cd metal salts. 1 is a 2D hcb framework and 2 is a 2D sql network. Their applications in detecting metal and inorganic ions were also explored. The results indicate that 1 exhibits dual-responsive photoluminescence sensing for Fe3+ and Cr2O72- ions while 2 can detect Hg2+ and Cr2O72- ions.

The combination of π-conjugated fluorophores within a hybrid system gives rise to a triphenylamine-functionalized material [Zn(bpba)(NO3)] (1) (Hbpba = 4-(bis(4-(pyridin-4-yl)phenyl)amino)benzoic acid). Compound 1 features a 2D + 2D → 2D parallel polycatenation structure with 63-hcb net. Photophysical studies revealed that the title phase showed superior sensitivity towards p-nitroaniline (p-NA) with a low detection limit (down to ∼0.10 ppm). Specifically, following a new detection route, vapor-sensing experiments using a saturated ethanol solution of nitroaromatic isomers have been established for the first time. Highly sensitive and selective detection of p-NA by the proposed material with a rapid response time (t = 30 s, QE > 90.0%) as compared to that via the control isomers (t = 60s, QE < 6.0%) demonstrates an attractive feasible route and a promising luminescent sensor for nitroaromatic detection.

Three zinc metal-organic frameworks (MOFs), {ZnL(chd)} n (1), {[Zn(L) 0.5 (oba)]·DMF·H 2 O} n (2) and {[Zn(L) 0.5 (sdb)]·H 2 O} n (3) [L = E,E-2,5-dihexyloxy-1,4-bis-(2-pyridin-vinyl)-benzene; H 2 chd = 1,4-cyclohexanedicarboxylic acid, H 2 oba = 4,4'-oxybisbenzoic acid, H 2 sdb = 4,4'-sulfonyldibenzoic acid], have been hydrothermally synthesized. We explored their applications in detecting ions, and the result shows that they all show highly selective sensing for Fe 3+ and Cr 2 O 7 2- ions.

Enantiomorphism and enantioselectivity are critical in biology and many other applications. Herein, we report two 3D chiral MOFs {[Zn 6 (MIDPPA) 3 (1,2,4-btc) 3 (NO 2 ) 3 (H 2 O) 3 ](H 2 O) 7 } n (1L and 1R) based on achiral ligands with high enantiomeric excess and a novel topological type. The internal mechanism of spontaneous chiral symmetry breaking, during the crystallization of chiral MOFs based on achiral ligands, is elucidated for the first time from both structural and theoretical aspects. Hydrogen bonds are found to play a key role in the spontaneous symmetry breaking of chiral MOFs. Also, DFT calculations support our findings from the aspects of total energies and HOMO-LUMO energy gaps. Both 1L and 1R, exhibiting green fluorescence, present a non-centrosymmetric polar packing arrangement, resulting in good ferroelectric behaviors and second-order nonlinear optical effects.

Four Cd(ii)-based compounds (1-4) were synthesized from solvothermal reactions involving the in situ aldimine condensation of an o-diamino-functionalized precursor 3,6-di(4H-imidazol-4-yl)benzene-1,2-diamine (L), Cd(NO 3 ) 2 ·4H 2 O and aldehyde. Two modes of cycloaddition ([4 + 1] cycloaddition and [4 + 2] cycloaddition) occurred during condensation, causing the in situ generation of two benzimidazole derivative ligands (L1 and L3) and a quinoxaline derivative ligand (L2). Furthermore, the chemical selectivity of the condensation was studied, where the condensation of o-diamino and the aldehyde is more stable and easy to operate. This strategy enriches the synthesis method of MOFs. Additionally, compound 2 containing uncoordinated quinoxaline N atoms showed excellent luminescent sensitivity for Fe 3+ detection.

A new copper-based coordination compound Cu 2 (2,2'-bipy) 2 (pfbz) 4 (1) (where 2,2'-bipy = 2,2'-bipyridine; pfbz = pentafluorobenzoate), was hydrothermally synthesized and structurally characterized. Compound 1 having a binuclear structure consists of two copper cations and two oxygen atoms alternately in a plane square arrangement. In the presence of very small amounts of H 2 O 2 , the catalytic properties of compound 1 for the degradation of methyl orange (MO) are excellent in the absence of UV-visible radiation. Moreover, compound 1 presents suitable properties for degradation of Congo red (CR). Our results indicated that the five-coordinated copper compound, 1, will be a promising candidate for efficient degradation of organic dyes.

Three new coordination polymers have been synthesized based on three linear pyridine ligands with different side chains and one flexible V-shaped dicarboxylate co-ligand: {[Co(L1) 0.5 (sdb)]} n (1), {[Co(L2) 0.5 (sdb)]·1.5H 2 O} n (2) and {[Co(L3) 0.5 (sdb)]·2DMF} n (3) (L1 = E,E-2,5-dioctyloxy-1,4-bis-[2-pyridin-vinyl]-benzene; L2 = E,E-2,5-dibutoxy-1,4-bis-[2-pyridin-vinyl]-benzene; L3 = E,E-2,5-dimethoxy-1,4-bis-[2-pyridin-vinyl]-benzene; H 2 sdb = 4,4'-sulfonyldibenzoic acid). Complexes 1-3 are 4-connected sql nets with a point symbol of {4 4 ·6 2 }. The interpenetration forms and porosity of frameworks have been well controlled by side chain prolongation. A larger steric hindrance for the pendant -O n Oct and -O n But groups leads to a larger repulsive force between the layers and effective construction of inclined polycatenations. A smaller steric hindrance for the pendant -Me group leads to the formation of a parallel stacked network. Therefore, compounds 1 and 2 feature 3D structures with inclined polycatenation (2D + 2D → 3D); compound 3 exhibits a non-interpenetrated 2D + 2D → 2D parallel stacked network. These complexes have been characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction measurements. In addition, the gas adsorption properties of the compounds have also been explored.

Chiral coordination polymers have attracted much attention due to their special properties and significant applications. In this work, we synthesized two non-centrosymmetric ligands, N,N-bis(4-(1H-imidazol-1-yl)phenyl)-4-(pyridin-4-yl)aniline (DIMPPA) and N-(4-(1H-imidazol-1-yl)phenyl)-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl)phenyl)aniline (MIDPPA), via structural modification of two reported centrosymmetric ligands; after that achiral → chiral induction occurred in the construction of three coordination polymers namely {[Cd(DIMPPA)(5-OH-bdc)](H2O)}n (1), {[Co(DIMPPA)(5-OH-bdc)](H2O)}n (2) and {[Cd2(MIDPPA)2(D-ca)2(H2O)2](H2O)5}n (3), when replacing the reported centrosymmetric ligands with non-centrosymmetric ligands (5-OH-H2bdc = 5-hydroxyisophthalic acid, D-H2ca = D-camphoric acid). Isostructural complexes 1 and 2 exhibit chiral 2D → 3D frameworks with the coexistence of polyrotaxane and parallel polycatenation features. Complex 3 shows two-fold interpenetrating 3D chiral architecture with cds-type topology. The luminescence emissions of both complexes 1 and 3 are mostly assignable to the internal π→π* electron transition in DIMPPA and MIDPPA, respectively. Complex 3 can satisfy the fundamental requirement of second-order nonlinear optical materials.

Three new Co-based MOFs with a nanosized tetradentate pyridine ligand, N,N,N′,N′-tetrakis(4-(4-pyridine)-phenyl) biphenyl-4,4′-diamine (TPPBDA) and carboxylate co-ligands, [Co(TPPBDA)(NO3)2]n·2H2O (1), [Co2(TPPBDA)(bpdc)2 (H2O)]n·2DMA (2) and [Co(TPPBDA)0.5(hfipbb)(H2O)]n·3.5H2O (3) (H2bpdc = biphenyldicarboxylic acid, H2hfipbb = 4,4′-(hexafluoroisopropylidene)bis-(benzoic acid), DMA = N,N-dimethylacetamide) have been synthesized under hydrothermal conditions. For complex 1, a large cavity causes a 4-fold interpenetration of the network, which can be classified as a type IIIa mode of interpenetration. Complex 2 reveals a non-interpenetrating three-dimensional (3D) framework based on the [Co2(μ2-H2O)(CO2)2] unit. Complex 3 is also a 2-fold interpenetrating 3D net based on the [Co2(CO2)2] cluster. These mononuclear or dinuclear cluster units are interconnected by TPPBDA and carboxylate co-ligands, resulting in interesting structural diversities and various degrees of interpenetration.

Four coordination polymers with different metal ions have been synthesized based on a rigid linear pyridine and a flexible V-shaped dicarboxylate ligand (L = 4,4'-(2,5-dimethoxy-1,4-phenylene)dipyridine; H2OBA = 4,4'-oxydibenzoic acid): {[Co(L)(OBA)]·2H2O}n (1), [Zn(L)(OBA)·2H2O]n (2), {[Ni(L)(OBA)]·DMF·H2O}n (3), [Cd(L)(OBA)]·DMF·H2O}n (4). The reaction conditions are similar except for the metal ions for complexes 1-4. Complexes 1 and 2 present a 3D unprecedented hxg-d-4-Cccm net, but 3 and 4 are 4-connected sql nets with a point symbol {4(4)·6(2)}. These complexes were characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction measurements. The UV-visible spectra, fluorescence, and gas adsorption properties of the compounds were also explored.

Five new metal complexes, {[Ni(DIDP)(m-bdc)(H2O)]·5H2O}n (1), {[Zn(DIDP)(hfipbb)]·2DMA}n (2), {[Zn(DIDP)(4,4'-sdb)]·H2O}n (3), {[Co(DIDP)(p-bdc)]}n (4), and {[Co2(DIDP)(hfipbb)2]·H2O}n (5), have been synthesized by reactions of the corresponding metal ions with a V-shaped ligand 2,8-di(1H-imidazol-1-yl)dibenzothiophene (DIDP) and different aromatic dicarboxylic acids, namely isophthalic acid (m-H2bdc), terephthalic acid (p-H2bdc), 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), and 4,4'-sulfonyldicarboxylic acid (4,4'-H2sdb), respectively. The structures of the complexes were determined by X-ray single-crystal diffraction. Complex 1 is a 1D chain structure containing a one-dimensional channel along the a direction and is further extended via O-H···S hydrogen bonds and C-H···π stacking interactions into a 3D framework. Complex 2 exhibits a quasi 2D + 2D → 2D with parallel polycatenation of 2D (4, 4) nets. Complex 3 displays an unusual 2D + 2D → 3D parallel polycatenated framework based on a 2D 6(3)-hcb network. Complex 4 shows a 2D 4-connected {4(4)·6(2)}-sql network containing a one-dimensional channel along the b direction. The adjacent 2D networks are further extended via C-H···O hydrogen bonds into a 3D supramolecular framework. Complex 5 features a 2-fold interpenetrating 3D framework with a 6-connected {4(12)·6(3)} pcu topology. Furthermore, the thermal stability for 1-5 and luminescence properties of 2 and 3 have been studied. Moreover, the solid-state UV-visible spectroscopy experiments show that complexes 1-5 are all optical semiconductors with band gaps of 3.06, 3.18, 3.23, 2.98, and 3.17 eV, respectively.

The solvothermal reactions of 1,1'-oxybis[3,5-di-4-pyridine]-benzene (L) and transition metal cations (Co and Ni) afford five novel coordination polymers in the presence of flexible bridging ligands (4,4'-H2nba = 4,4'-dicarboxydiphenylamine, H2cam = d-camphoric acid, 4,4'-H2sdb = 4,4'-sulfonyldibenzoic acid, H2chdc = 1,4-trans-cyclohexanedicarboxylic acid), namely {[Co2L2(OH)2(nba)]·2DMF}n (), {[CoL(cam)(H2O)]}n (), {[Co3(L)(4,4'-sdb)3(H2O)]·1.5CH3CN·4H2O}n (), {[Ni3(L)(4,4'-sdb)3(H2O)]·1.5CH3CN·4H2O}n (), and {[Ni2L2(chdc)2(H2O)2]·(H2O)3}n () (DMF = N,N-dimethylformamide). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, and powder X-ray diffraction. Complex reveals a 2-fold interpenetrating three-dimensional (3D) framework with the Schläfli symbol {4·8·10(4)}{4·8·10} topology. Compound crystallizes in the achiral space group with the d-camphorate ligand racemized. Compounds and reveal similar structure with the {3·4(4)·6}{3(2)·4(8)·5(9)·6(9)} topology based on a linear trinuclear building block M3(OOCR)6 (M = Co(ii) or Ni(ii)). Compound is a wavy sheet, where both carboxylate and L ligands act as bidentate ligands. Moreover, UV-Visible absorption spectra of complexes , and the magnetic properties of have been investigated.

Three new isomorphic coordination polymers of Co(2+), Zn(2+) ions with flexible multicarboxylic acid ligand of the cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid (H(4)L), [Co(4)L(2)(H(2)O)(8)]·3H(2)O (1), [Zn(4)L(2)(H(2)O)(8)]·3H(2)O (2) and [Co(0.8)Zn(3.2)L(2)(H(2)O)(8)]·3H(2)O (3), have been synthesized under hydrothermal conditions and by means of controlling the pH of the reaction mixtures (with an initial pH of 6.0 for 1, 4.0 for 2, and 5.0 for 3, respectively). In the crystal of 1, two crystallographically different Co(2+) ions (Co1 and Co2) form a negatively-charged coordination polymeric chain, which contains a centrosymmetric, linear, trinuclear Co(2+) cluster (Co(3)L(2)) subunit; another crystallographically independent Co(2+) ion (Co3) coordinated to six water molecules acts as a counter ions to link the neighboring coordination polymeric chains via intermolecular H-bond interactions. The Co(2+) ions in 1 were completely and partially replaced by Zn(2+) ions to give 2 and 3, respectively. Complex 3 shows a novel molecular alloy nature, due to the random distributions of the Co(2+) and Zn(2+) ions. Three isomorphic complexes exhibit distinct thermal decomposition mechanisms. The deprotonated cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid ligands decompose at 420-750 °C to give the residue CoO in 1, ZnO + C in 2 and CoO + ZnO in 3. Complex 1 shows a complicated magnetic behavior with co-existence of antiferromagnetic exchange interactions between neighboring Co(2+) ions as well as strong spin-orbital coupling interactions for each Co(2+) ion; complex 3 exhibits a magnetically isolated high-spin Co(2+) ion behavior with strong spin-orbital coupling interactions., (© The Royal Society of Chemistry 2011)

The self-assembly of 3,5-pyrazoledicarboxylic acid (H3pdc) and metal salts under hydrothermal conditions leads to the formation of a series of novel NaI-CuII-LnIII heterometallic coordination polymers, [[Na(H2O)4]2[Cu(pdc)2Ln(H2O)5]2 x 3H2O]n [Ln = La (1); Sm (2); Pr (3); Nd (4) and pdc3- = 3,5-pyrazoledicarboxylate]. X-Ray structure analyses show that these complexes all exhibit pairs of infinite, unexpected, cationic and anionic chains. It is the first successful attempt to construct unprecedented NaI-CuII-LnIII heterometallic coordination polymers with both infinite cationic and anionic chains. These four complexes show homologous thermal stabilities. The different magnetic properties of are also been reported in this paper.