The reactions of isonicotinic acid analogues, 4-quinolinecarboxylic acid (HL1) and 9-acridinecarboxylic acid (HL2) with M(NO3)2 (M = ZnII and CdII) in the presence of Et3N in MeOH (or EtOH) led to the formation of four new complexes, [Zn(L1)2(H2O)]∞ (1), [Zn(L2)2(MeOH)2]3·(H2O)1.5 (2) and [Cd(L2)2(MeOH)2]3·(H2O)1.5 (3) and [Cd(L2)2(EtOH)2]3·(H2O)0.5 (4). Single crystal X-ray diffraction analyses revealed that the ZnII and CdII complexes of the same ligand (L1 or L2) are isostructural, with 1 taking a 1D chain structure, with 2–4 being trinuclear complexes. In such complexes, the carboxylate groups adopt a bidentate syn,syn-bridging coordination fashion to bridge adjacent metal centers. The N donors do not take part in the coordination, but form O–H⋯N hydrogen bonds with the coordinated water or MeOH (or EtOH), leading to the formation of 3D frameworks. The effects of π–π stacking and the structural differences between these complexes and those with isonicotinic acid were also discussed.
The oxygen evolution reaction (OER) in water splitting plays a critical role in some clean energy production systems. Transition-metal oxides as one of the most common OER electrocatalysts have been widely explored; however, their activity is limited by low electrical conductivity, slow mass transfer, and inadequate active sites. Herein, we develop a feasible strategy in which layered two-dimensional metal–organic frameworks (2D MOFs) act as templates to construct metal oxide/carbon (MOx/C, M = Co, Ni, and Cu) nanosheet arrays for the OER. Because of improved conductivity and more exposed active sites afforded by their 2D structures with rich hierarchical pores and the incorporation with porous carbon, these 2D MOF-derived MOx/C arrays present high electrocatalytic activities and good durability. Particularly, Co3O4/CBDC, NiO/CBDC, and Cu2O/S–CTDC exhibit low overpotentials of 208, 285, and 313 mV at the current density of 10 mA cm–2, respectively, outperforming all previously reported corresponding metal oxide-based catalysts.
To explore the relationships between the structures of ligands and their complexes, we have synthesized and characterized a series of metal complexes with two structurally related ligands, 9-acridinecarboxylic acid (HL(1)) and 4-quinolinecarboxylate acid (HL(2)), [Cu(2)(mu(2)-OMe)(2)(L(1))(2)(H(2)O)(0.69)](n) 1, [Cu(2)(L(1))(4)(CH(3)OH)(2)] 2, [Cu(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 3, [Mn(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 4, [Co(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 5, [Cu(L(2))(2)](n) 6, [Mn(L(2))(2)(H(2)O)](n) 7, and [Co(L(2))(2)(H(2)O)](n) 8. 1 is a three-dimensional (3D) polymer with an interpenetrating NbO type network showing one-dimensional (1D) channels, whereas 2 and 3 take bi- and trinuclear structures, respectively, because of the differences in basicity of the reaction systems in preparing the three complexes. 4 and 5 have trinuclear structures similar to that of 3. In 1-5, ligand L(1) performs different coordination modes with N,O-bridging in 1 and O,O'-bridging in 2-5, and the metal ions also show different coordination geometries: square planar in 1, square pyramidal in 2, and octahedral in 3-5. 6 has a two-dimensional structure containing (4,4) grids in which L(2) adopts the N,O-bridging mode and the Cu(II) center takes square planar geometry. 7 and 8 are isostructural complexes showing 1D chain structures, with L(2) adopting the O,O-bridging mode. In addition, the intermolecular O-H...N hydrogen bonds and pi-pi stacking interactions further extend the complexes (except 1 and 6), forming 3D structures. The magnetic properties of 2-7 have been investigated and discussed in detail.
Abstract In principle, porous physisorbents are attractive candidates for the removal of volatile organic compounds such as benzene by virtue of their low energy for the capture and release of this pollutant. Unfortunately, many physisorbents exhibit weak sorbate–sorbent interactions, resulting in poor selectivity and low uptake when volatile organic compounds are present at trace concentrations. Herein, we report that a family of double-walled metal–dipyrazolate frameworks, BUT-53 to BUT-58, exhibit benzene uptakes at 298 K of 2.47–3.28 mmol g −1 at <10 Pa. Breakthrough experiments revealed that BUT-55, a supramolecular isomer of the metal–organic framework Co(BDP) (H 2 BDP = 1,4-di(1 H -pyrazol-4-yl)benzene), captures trace levels of benzene, producing an air stream with benzene content below acceptable limits. Furthermore, BUT-55 can be regenerated with mild heating. Insight into the performance of BUT-55 comes from the crystal structure of the benzene-loaded phase (C 6 H 6 @BUT-55) and density functional theory calculations, which reveal that C–H···X interactions drive the tight binding of benzene. Our results demonstrate that BUT-55 is a recyclable physisorbent that exhibits high affinity and adsorption capacity towards benzene, making it a candidate for environmental remediation of benzene-contaminated gas mixtures.
To investigate the influences of the geometries of pendant carboxylate ligands and some intramolecular/intermolecular weak interactions on the structures of transition metal complexes, five new Cd(II) complexes, Cd2(HL1)2(L2)4 (1), Cd2(HL1)2(L3)4 (2), {[Cd2(HL1)(L4)4(H2O)2](H2O)}∞ (3), [Cd(L1)(L5)]∞ (4), and Cd2(L1)2(HL1)2(L4)2 (5) (HL1 = 3-(2-pyridyl)pyrazole, HL2 = benzoic acid, HL3 = naphthalene-carboxylic acid, HL4 = 9-anthracene-carboxylic acid, and HL5 = isonicotinic acid), have been synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. 1 and 2 have a similar dinuclear structure, which is further assembled to form a one-dimensional (1D) chain by π···π stacking and/or hydrogen-bonding interactions. 3 possesses a 1D chain structure that is further interlinked via intermolecular π···π stacking, resulting in a two-dimensional (2D) network, while 4 has a 2D (4,4) network with channel dimension of 9.34 × 9.34 Å2 and further assembles into a three-dimensional (3D) network by interlayer π···π stacking. 5 also possesses a dinuclear structure and then forms a 2D network through intermolecular π···π stacking and C−H···O hydrogen-bonding interactions. Interestingly, 3 and 5 were obtained simultaneously in the same reaction system. The structural differences of those complexes show the influences of the geometries of the pendant carboxylate ligands. This result also shows that intramolecular/intermolecular weak interactions play important roles in the formation of coordination architectures, especially in the aspect of linking multinuclear discrete subunits or low-dimensional entities into high-dimensional supramolecular frameworks. In addition, complexes 1, 2, and 4 exhibit blue emission in the solid state at room temperature.
Constructing stable palladium(II)-based metal–organic frameworks (MOFs) would unlock more opportunities for MOF chemistry, particularly toward applications in catalysis. However, their availability is limited by synthetic challenges due to the inertness of the Pd–ligand coordination bond, as well as the strong tendency of the Pd(II) source to be reduced under typical solvothermal conditions. Under the guidance of reticular chemistry, herein, we present the first example of an azolate Pd-MOF, BUT-33(Pd), obtained via a deuterated solvent-assisted metal metathesis. BUT-33(Pd) retains the underlying sodalite network and mesoporosity of the template BUT-33(Ni) and shows excellent chemical stability (resistance to an 8 M NaOH aqueous solution). With rich Pd(II) sites in the atomically precise distribution, it also demonstrates good performances as a heterogeneous Pd(II) catalyst in a wide application scope, including Suzuki/Heck coupling reactions and photocatalytic CO2 reduction to CH4. This work highlights a feasible approach to reticularly construct noble metal based MOFs via metal metathesis, in which various merits, including high chemical stability, large pores, and tunable functions, have been integrated for addressing challenging tasks.
Abstract The development of ethane (C 2 H 6 )‐selective adsorbents for ethylene (C 2 H 4 ) purification, although challenging, is of prime industrial importance. Pillared‐layer metal‐organic frameworks (MOFs) possess facilely tunable pore structure and functionality, which means they have excellent potential for high‐performance C 2 H 6 /C 2 H 4 separation applications. Herein, we report a family of isostructural pillared‐layer MOFs with various metal centers M and co‐ligands L, M 2 (D‐cam) 4 L 2 (denoted M‐cam‐L; M = Cu, Co, Ni; L = pyz, apyz, dabco), with a variety of pore surface properties. All of the M‐cam‐L materials exhibit preferential adsorption for C 2 H 6 over C 2 H 4 . In particular, Ni‐cam‐pyz exhibits the highest C 2 H 6 capture capacity (68.75 cm 3 g −1 at 1 bar and 298 K), Cu‐cam‐dabco possesses the greatest C 2 H 6 /C 2 H 4 adsorption selectivity (2.3), and the lowest isosteric heat of adsorption is demonstrated for Cu‐cam‐pyz (20.1 kJ mol −1 ). Dynamic column breakthrough experiments also confirmed the excellent separation performance of M‐cam‐pyz and M‐cam‐dabco materials. The synthesis route of the M‐cam‐L materials is easily scaled‐up under laboratory conditions, and hence this class of MOFs is promising for practical C 2 H 4 purification.
To improve phycocyanin holo-α subunit (cpcA) production from Escherichia coliBL21 (DE3) cells, culture medium was screened and optimized using the statistical experimental designs of Plackett-Burman and response surface methodology. In the first step, one-factor-at-a-time method was used to evaluate the effect of carbon sources and nitrogen sources on the yield of cpcA. A two-level Plackett-Burman design was then adopted to select the most important nutrients influencing the cpcA production, which showed that beef extract, KH2PO4 and K2HPO4·3H2O were the most significant ingredients (P< 0.05). Finally, response surface Box-Behnkendesign was employed to develop a mathematical model to identify the optimum concentrations of the key components for higher cpcA production, which revealed these as follows: beef extract (2.22%, w/v), KH2PO4 (0.52%, w/v), K2HPO4·3H2O(0.94%, w/v). The high correlation between the predicted and observed values indicated the validity of the model. CpcA yield increased significantly with optimized medium (47.62 mg/L) when compared with original medium (2.72 mg/L).
Key words: Phycocyanin holo-α subunit, Plackett-Burman design, optimization, response surface methodology.
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