Pore Environment Optimization of Microporous Metal-Organic Frameworks with Huddled Pyrazine Pillars for C2H2/CO2 Separation.

Metal-organic frameworks (MOFs) have been proven promising in addressing many critical issues related to gas separation and purification. However, it remains a great challenge to optimize the pore environment of MOFs for purification of specific gas mixtures. Herein, we report the rational construction of three isostructural microporous MOFs with the 4,4',4"-tricarboxyltriphenylamine (H3TCA) ligand, unusual hexaprismane Ni6O6 cluster, and functionalized pyrazine pillars [PYZ-x, x = -H (DZU-10), -NH2 (DZU-11), and -OH (DZU-12)], where the building blocks of Ni6O6 clusters and huddled pyrazine pillars are reported in porous MOFs for the first time. These building blocks have enabled the resulting materials to exhibit good chemical stability and variable pore chemistry, which thus contribute to distinct performances toward C2H2/CO2 separation. Both single-component isotherms and dynamic column breakthrough experiments demonstrate that DZU-11 with the PYZ-NH2 pillar outperforms its hydrogen and hydroxy analogues. Density functional theory calculations reveal that the higher C2H2 affinity of DZU-11 over CO2 is attributed to multiple electrostatic interactions between C2H2 and the framework, including strong C≡C···H-N (2.80 Å) interactions. This work highlights the potential of pore environment optimization to construct smart MOF adsorbents for some challenging gas separations.

Interpenetrated metal-organic frameworks with enhanced photoluminescence for selective recognition of m-xylene from xylene isomers.

Two novel luminescent metal-organic frameworks (MOFs), [Zn3(TCA)2(BPB)2]n (DZU-101, where H3TCA = 4,4',4''-tricarboxyltriphenylamine and BPB = 1,4-bis(pyrid-4-yl)benzene) and [Zn3(TCA)2(BPB)DMA]n (DZU-102), based on the same ligands and metal ions were synthesized by regulating the amount of water in the solvothermal reaction system. Structural analyses show that the two MOFs have pillar-layered frameworks with Zn3 clusters connected by the TCA3- and BPB ligands. Interestingly, DZU-102 possessed a two-fold interpenetrated framework distinct from the individual network of DZU-101. As a result, DZU-102 showed a visual fluorescence color change from chartreuse to azure in m-xylene, while the fluorescence color was turquoise in p-/o-xylene with no change. Furthermore, compared with p/o-xylene, the fluorescence emission peak of DZU-102 in m-xylene suspension produced an obvious blue shift. Moreover, selective fluorescence sensing experiments were also carried out, which demonstrated that the degree of peak shift was related to the concentration of m-xylene, indicating the potential application of DZU-102 in fluorescence sensing of m-xylene from xylene isomers and further revealed the application of structural interpenetration for luminescence tuning of MOFs.

Mechanism of hysteresis in shock wave reflection.

This paper reports on the mechanism of the hysteresis in the transition between regular and Mach shock wave reflections. We disclose that, for a given inflow Mach number, a stable reflection configuration should maintain the minimal dissipation. As the wedge angle varies, the set of the minimal dissipation points forms the valley lines in the dissipation landscape, and these valley lines compose the hysteresis loop. The saddle-nodes, intersections of the ridge line, and the valley lines are actually the transition points. Additionally, the predicted reflection configurations agree well with the experimental and numerical results, validating this theory.

Synthesis and in vitro antitumor activity evaluation of copper(II) complexes with 5-pyridin-2-yl-[1,3]dioxolo[4,5-g]isoquinoline derivatives.

Seven Cu(II) complexes with 5-pyridin-2-yl-[1,3]dioxolo[4,5-g]isoquinoline derivatives as ligands: [Cu2(L1)2Cl4] (1), [Cu(L2)Cl2] (2), [Cu(L1)(NO3)2] (3), [Cu(L2)(NO3)2] (4), [Cu(L3)Cl2] (5), [Cu(L3)Br2] (6) and [Cu(L3)(NO3)2] (7){L1=9-nitro-5-pyridin-2-yl-[1,3]dioxolo[4,5-g]isoquinoline, L2=4-nitro-5-pyridin-2-yl-[1,3]dioxolo[4,5-g]isoquinoline, L3=9-bromo-5-pyridin-2-yl-[1,3]dioxolo[4,5-g]isoquinoline}, were synthesized and characterized. Their in vitro anticancer activities against T-24, MGC-80-3, HeLa, Hep-G2, A549 and SK-OV-3 were evaluated. Compared with their corresponding ligands, most of these complexes exhibited enhanced anticancer activities in contrast to their corresponding ligands and copper salt. Among them, complexes 1 and 3 displayed selective cytotoxicity to HeLa cells comparing with normal liver cell HL-7702, with IC50 values of 5.03 ±â€¯1.20 µM and 10.05 ±â€¯0.52 µM, respectively. Complexes 1 and 3 inhibited telomerase activity by interacting with c-myc promoter elements, and therefore exerted their antitumor activity. Furthermore, complexes 1 and 3 could trigger cell apoptosis via disruption of mitochondrial pathway through notably increased reactive oxygen species (ROS) levels, loss of mitochondrial membrane potential (Δψm), increase of the cytochrome c and apaf-1, decrease of bcl-2, and activation of caspases 3/9. Complexes 1 and 3 exhibited enhanced cytotoxicity, presenting synergetic effect after the ligands coordinated to copper(II) center.