High Adsorption Capacity and Selectivity of SO2 over CO2 in a Metal-Organic Framework.

Herein, we report a new metal-organic framework (MOF), namely, ECUT-77, which is built on rod-shaped secondary building units, showing a high Brunauer-Emmett-Teller surface area of 760.3 cm2/g, a pore volume of 0.4 cm3/g, and an aperture of about 1 nm. This MOF enables both high SO2 adsorption capacity up to 8.0 mmol/g at 0.92 bar and room temperature and a high SO2/CO2 selectivity of 44, resulting in excellent SO2 separation upon a ECUT-77 column from a SO2/CO2 mixture containing 2000 ppm of SO2.

The MOF+ Technique: A Significant Synergic Effect Enables High Performance Chromate Removal.

A significant synergic effect between a metal-organic framework (MOF) and Fe2 SO4 , the so-called MOF+ technique, is exploited for the first time to remove toxic chromate from aqueous solutions. The results show that relative to the pristine MOF samples (no detectable chromate removal), the MOF+ method enables super performance, giving a 796 Cr mg g-1 adsorption capacity. The value is almost eight-fold higher than the best value of established MOF adsorbents, and the highest value of all reported porous adsorbents for such use. The adsorption mechanism, unlike the anion-exchange process that dominates chromate removal in all other MOF adsorbents, as unveiled by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), is due to the surface formation of Fe0.75 Cr0.25 (OH)3 nanospheres on the MOF samples.

Significant Enhancement of C2 H2 /C2 H4 Separation by a Photochromic Diarylethene Unit: A Temperature- and Light-Responsive Separation Switch.

A dual temperature- and light-responsive C2 H2 /C2 H4 separation switch in a diarylethene metal-organic framework (MOF) is presented. At 195 K and 100 kPa this MOF shows ultrahigh C2 H2 /C2 H4 selectivity of 47.1, which is almost 21.4 times larger than the corresponding value of 2.2 at 293 K and 100 kPa, or 15.7 times larger than the value of 3.0 for the material under UV at 195 K and 100 kPa. The origin of this unique control in C2 H2 /C2 H4 selectivity, as unveiled by density functional calculations, is due to a guest discriminatory gate-opening effect from the diarylethene unit.

Photoswitching CO2 capture and release in a photochromic diarylethene metal-organic framework.

We demonstrate herein a promising pathway towards low-energy CO2 capture and release triggered by UV and visible light. A photosensitive diarylethene ligand was used to construct a photochromic diarylethene metal-organic framework (DMOF). A local photochromic reaction originating from the framework movement induced by the photoswitchable diarylethene unit resulted in record CO2-desorption capacity of 75% under static irradiation and 76% under dynamic irradiation.

Optimization of reaction conditions towards multiple types of framework isomers and periodic-increased porosity: luminescence properties and selective CO2 adsorption over N2.

Three new metal-organic frameworks (MOFs) were prepared by solvo(hydro)thermolysis and further characterized as framework isomers. The structural transformation from non-porous to porous MOFs and the purity of these products can be modulated by controlling the reaction temperature. The periodic-increased porosity observed was further confirmed by CO2 adsorption isotherms. Owing to the presence of acylamide groups in the pore walls and the flexible nature of the skeleton of these MOFs, highly selective CO2 adsorption over N2 was observed, as well as structure-dependent periodic varieties in luminescence properties.

Determination of trace lithium in uranium compounds by adsorption on activated alumina using a micro-column method.

A novel method using a micro-column packed with active alumina as solid phase was proposed for separation of trace lithium from uranium compounds prior to determination. The method is based on a preliminary chromatographic separation of the total amount of uranium. This separation involves passing the solution containing sodium carbonate through active alumina and then eluting the trace lithium retained by the solid phase with a solution of sulfuric acid. Two modes, off-line and on-line micro-column preconcentration, were performed. In conjunction with atomic absorption spectrometry, this on-line preconcentration technique allows a determination of lithium at 10(-9) level. Both off-line and on-line mode operation conditions were investigated in separation and determination of trace lithium by micro-column method (length of column bed, flow rate, etc.). The adsorption capacity of activated alumina was found to be 343 microg g(-1) for lithium. Under the optimal operation condition, the detection limit (DL) of on-line preconcentration corresponding to three times the standard deviation of the blank (S/N = 3) was found to be 1.3 ng mL(-1) and the RSD of this method is 3.32% (n = 5). The on-line calibration graph was linear over the range 20 - 200 ng mL(-1). A good preconcentration factor 820 was achieved by experiment under the on-line mode. The developed method was applied to the analysis of trace lithium in nuclear grade uranium compounds.

Applying MOF+ technique for in situ preparation of a hybrid material for hydrogenation reaction.

In this study, we present the first case of applying the MOF+ technique for in situ preparation of a hybrid material, namely, Zn-MOF-74@ (Pd@Fe2O3). This as-synthesized material can well maintain both the integrity of the framework and porosity. Notably, Zn-MOF-74@(Pd@Fe2O3) exhibits outstanding catalytic performance in the hydrogenation reaction of alkene and semihydrogenation reaction of phenylacetylene, thus providing a new guideline for the design of MOF-based hybrid materials for catalytic purpose.

Coumarin-modified microporous-mesoporous Zn-MOF-74 showing ultra-high uptake capacity and photo-switched storage/release of U(VI) ions.

Driven by an energy crisis but consequently puzzled by various environmental problems, uranium, as the basic material of nuclear energy, is now receiving extensive attentions. In contrast to numerous sorbents applied in this field, metal-organic framework (MOFs), as a renovated material platform, has only recently been developed. How to improve the adsorption capacity of MOF materials towards U(VI) ions, as well as taking advantage of the nature of these MOFs to design photo-switched behaviour for photo-triggered storage/release of U(VI) ions are at present urgent problems and great challenges to be solved. Herein, we show a simple and facile method to target the goal. Through coordination-based post-synthetic strategy, microporous- mesoporous Zn-MOF-74 was easily functionalized by grafting coumarin on coordinatively unsaturated Zn(II) centers, yielding a series of coumarin-modified Zn-MOF-74 materials. The obtained samples displayed ultra-high adsorption capacity for U(VI) ions from water at pH value of 4 with maximum adsorption capacities as high as 360 mg/g (the record value in MOFs) and a remarkable photo-switched capability of 50 mg/g at pH value of 4. To the best of knowledge, and in contrast to the well-known photo-switched behaviour towards CO2, dye (propidium iodide), as well as fluorescence observed in MOFs, this is the first study that shows a photo-switched behaviour towards radioactive U(VI) ions in aqueous solution.

MOF catalysis of Fe(II)-to-Fe(III) reaction for an ultrafast and one-step generation of the Fe2O3@MOF composite and uranium(vi) reduction by iron(ii) under ambient conditions.

Herein, we demonstrate that Zn-MOF-74 enables the ultrafast and one-step generation of the Fe2O3@MOF composite once Zn-MOF-74 contacts with FeSO4 solution. This unique reaction can be further applied in catalysis of U(vi) reduction by Fe(ii) under ambient conditions. The results provide a highly renovated strategy for U(vi) reduction by Fe(ii) just under ambient conditions, which completely subvert all established methods about U(vi) reduction by Fe(ii) in which O2- and CO2-free conditions are absolutely required.

An acylamide metal-organic framework with an unprecedented four-connecting trinodal topology and amide oxygen coordination.

The three-dimensional Zn(II) coordination polymer poly[[bis(µ2-benzene-1,4-dicarboxylato){µ4-N(1),N(3),N(5)-tris[(pyridin-3-yl)methyl]benzene-1,3,5-tricarboxamide}dizinc(II)] monohydrate], {[Zn2(C8H4O4)2(C27H24N6O3)]·H2O}n, is characterized by a rare (4,4,4)-connected (4.6(2).7(2).8)(4.6(2).7(3))(4(2).6(2).7(2)) topology. The tricarboxamide ligand adopts an unprecedented tetradentate coordination mode, with one carboxamide O atom participating in the coordination. The polymer was further characterized by thermogravimetric and solid-state luminescence analysis.

Exceptional temperature-dependent coordination sites from acylamide groups.

Herein, through altering the reaction temperature, the coordination mode of the acylamide ligand is well controlled with or without the oxygen coordination site. The resulting two new coordination polymers have the formulas Cd3(L)2(bdc)3·4(H2O) (1) and Cd(L)(bdc)·2(H2O) (2) (L = N(1),N(4)-bis(pyridin-3-ylmethyl)terephthalamide, H2bdc = terephthalic acid).

Solvent-induced reversible single-crystal-to-single-crystal transformations observed in lanthanide complexes.

In this work, a rare 0D→0D single-crystal-to-single-crystal transformation (SCSC) is observed in lanthanide compounds, which is triggered by the removal or retake of solvent molecules. This advantage prompted us to explore the magnetic property of them, and some interesting magnetic properties are obtained.

Framework isomers controlled by the speed of crystallization: different aggregation fashions of Zn(II) and 1,2,4-triazol-3-amine, distinct (3,4)-connected self-penetrating nets, and various pore shapes.

In this work, we report two exceptional framework isomers, Zn(L)(bdc)(0.5)·0.25H2O (1, HL = 1,2,4-triazol-3-amine, H2bdc = terephthalic acid) and Zn(L)(bdc)(0.5)·0.17H2O (2), where their formation is controlled by different speeds of crystallization. Further structural studies reveal that this operation of controlling the speed of crystallization may play a profound role in determining the aggregation fashions of Zn(II) ions and L(-) ligands, resulting in the various layers, viz. a 4·8(2) net vs. a 4·6·12 net. Importantly, this work also presents two previously unobserved (3,4)-connected self-penetrating matrixes.

A microporous metal-organic framework containing an exceptional four-connecting 4(2)6(4) topology and a combined effect for highly selective adsorption of CO2 over N2.

Reported here is a new microporous metal-organic framework, namely [Zn(2)(L)(btc)(Hbtc)] [NH(2)(CH(3))(2)]·(DMF)(2)(H(2)O)(4) (1), which is synthesized solvo(hydro)thermally by the self-assembly of Zn(NO(3))(2), N(4),N(4)-di(pyridin-3-yl)-[1,1'-biphenyl]-4,4'-dicarboxamide (L) and 1,3,5-benzenetricarboxylate acid (H(3)btc). Its topology can be described as a four-connecting 4(2)6(4) matrix containing both tetrahedral metal and ligand nodes. Interestingly, such a matrix has the same topology symbol as that observed in the well known sodalite (SOD) net, but the td10 of 434 is different from the td10 of 791 for the SOD net, indicative of an exceptional four-connecting 4(2)6(4) net. Another outstanding point is the highly selective adsorption of CO(2) over N(2), possibly contributed by a combined effect from the charged skeleton, the existence of functional groups of -CONH- and -COOH in 1.

Functionalizing the pore wall of chiral porous metal-organic frameworks by distinct -H, -OH, -NH2, -NO2, -COOH shutters showing selective adsorption of CO2, tunable photoluminescence, and direct white-light emission.

This work presents a prototype of chiral porous metal-organic framework with the porous wall decorated by different functional groups. The special structure in conjunction with the gas adsorption results reveals some relationship between CO2 adsorption and functional points. Moreover, outstanding tunable photoluminescence and direct white-light emission is observed.

Solvent-induced supramolecular isomers, structural diversity, and unprecedented in situ formation of both inorganic and organic ions in inorganic-organic mercury(II) complexes.

Reported here is, for the first time, an important study of solvent effect on structural diversity in inorganic-organic mercury(II) complexes. As a result, the first supramolecular isomer in mercury(II) complexes is obtained. Importantly, a previously unobserved in situ generation of both inorganic (Cl(-)) and organic ([CH(3)-L1-CH(3)](2+)) ions was also observed.

The application of single-crystal-to-single-crystal transformation towards adjustable SMM properties.

Reversible single-crystal-to-single-crystal transformation (SCSC) was for the first time observed between 4f-based molecular magnets.

A self-catenated network containing unprecedented 0D + 2D → 2D polycatenation array.

Herein, we report a new acylamide ligand and its application in the construction of a metal-organic framework. The resultant acylamide metal-organic framework, namely [Zn(2)(L)(OH)(btc)](n) (1, L = N(1),N(4)-bis(pyridin-3-ylmethyl) naphthalene-1,4-dicarboxamide, H(3)btc = benzene-1,3,5-tricarboxylic acid), was obtained by hydrothermal synthesis. The outstanding structural feature of it is the 0D + 2D → 2D polycatenation array containing a self-catenated feature which has never previously been observed. To the best of our knowledge, the coexistence of self-catenation and polycatenation phenomena is highly exceptional.

A series of 1D Dy(III) compound showing slow magnetic relaxation: synthesis, structure, and magnetic studies.

In this work, we present the synthesis, structure, and magnetic studies of three 1D homo-spin Dy(III) compounds in detail. For 1, one crystallography-independent Dy(III) site is contained and the coordination surrounding is a distorted square-antiprism geometry. Within 2, four crystallography-independent Dy(III) sites with largely distorted square-antiprism geometry are observed. As for 3, two crystallography-independent Dy(III) sites showing bicapped triangular-prism geometry are involved. The magnetic studies suggest weak ferromagnetic interactions for 1 and weak antiferromagnetic interactions for 2 and 3. Their dynamic magnetic properties are investigated by means of alternating current (ac) susceptibility measurement, revealing their slow magnetic relaxation. Moreover, a field-dependent ac signal is observed in 1, when by applying a static dc = 1000 Oe field, strong frequency-dependent ac signals and the peak of out-of-phase (χ'') can be clearly found. Ultimately, by fitting the Arrhenius law the energy barrier and relaxation time are estimated.

Chiral 1D Dy(III) compound showing slow magnetic relaxation.

Herein, we present one chiral Dy(III) compound, namely Dy(L)(3)(1, HL = 2-methylbenzoic acid), synthesized from the achiral HL ligand. Within 1, along a direction the seven-coordinated Dy(III) ion are bridged by double L carboxylate and single L oxygen to give rise to the 1D helical chain. The magnetic studies suggest small intra-chain ferromagnetic interactions. Alternating current (AC) magnetic measurements show a frequency dependence of magnetic susceptibilities in both in-phase, χ', and out-of-phase, χ''. However, no obvious peak can be found even under 1000 Oe static field, suggesting the prevalence of quantum tunnelling effect at low temperature.