Mixed matrix membranes containing fluorescent coordination polymers for detecting Cr2O72- with high sensitivity, stability and recyclability.

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.

Three coordination polymers built by quaternary-ammonium-modified isophthalic acid.

Three coordination polymers based on quaternary-ammonium-modified isophthalic acid, namely, catena-poly[[[aqua-µ2-bromido-di-µ3-hydroxido-methanoldinitratotetracopper(II)]-bis{µ4-5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylato}] nitrate], {[Cu4Br(C19H28NO5)2(NO3)2(OH)2(CH4O)(H2O)]NO3}n, 1, poly[µ3-bromido-µ2-bromido-bromido-µ3-hydroxido-{µ4-5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylato}tricopper(II)], [Cu3Br3(C19H28NO5)(OH)]n, 2, and poly[bromido{µ3-5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylato}zinc(II)], [ZnBr(C19H28NO5)]n, 3, were obtained by solvothermal reactions. Coordination polymer (CP) 1 contains tetranuclear Cu4 units, in which the four Cu atoms are linked by two µ3-OH- groups into a Cu4(OH)2 cluster, which are in turn linked by 5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylate (cpa-) ligands into a chain structure. CP 2 also contains a tetranuclear Cu4(OH)2 cluster and these are linked with CuBr3 units into chains. The chains are then connected by cpa- ligands into a two-dimensional layered structure. CP 3 contains a two-dimensional layer structure built by binuclear Zn2 units and cpa- ligands. The Br- counter-anions of the quaternary ammonium groups all take part in the construction of the polymeric networks.

Three metal-organic framework isomers of different pore sizes for selective CO2 adsorption and isomerization studies.

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 CO2 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 CdII, 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 CO2 over N2 and CH4, 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 CO2 adsorption. The effects of hydrothermal reaction conditions and additives on the structures and the formation of the MOF isomers were also studied.