RESUMEN
A new Cotton@Fe-BTC composite formed by Fe-BTC (BTC-H3: trimesic acid) metal framework (Fe-BTC MOF loading as high 38 wt %) supported by cellulose fiber is synthesized in aqueous media using a simple and green preparation method, described for the first time in this manuscript. This new strategy relies on the synergetic effect of the pure cellulose and MOFs frameworks resulting in hybrid nanofibers of MOFs@cellulose composite. A complete characterization of the composite material reveals its structural similarity to MIL-100(Fe), a Fe-BTC material. The Cotton@Fe-BTC composite potential use as an eco-friendly and low-cost adsorbent was evaluated for its adsorptive performance for the removal of dye belonging to the triarylmethane dye family (Malachite Green (MQ), Brilliant Green (BG), Pararosaniline (PR), Basic Fuchsine (BF), Crystal Violet (CV), Methyl Green (Met-G), Victoria Blue B (VB), Acid Fuchsin (AF) and Aniline Blue (AB)) in aqueous solution. The fast kinetics and high dye removal efficiencies (>90%) obtained in aqueous solutions. The structure of Cotton@Fe-BTC network, contributed to the remarkable adsorption properties towards a variety of triphenylmethanedye. The interparticle studies showed two main steps in the dye adsorption processes, with the exception of AF and BG. The equilibrium adsorption capacities qe (mg/g) follow the order: AF (3.64)
RESUMEN
Two polymorphic malonato-bridged copper(II) complexes of formula ([Cu(bpy)(H2O)][Cu(bpy)(mal)(H2O)])-(ClO4)2 (1 and 2) (bpy = 2,2'-bipyridine and mal = malonate dianion) have been prepared and their structures solved by X-ray diffraction methods. Compound 1 crystallizes in the monoclinic space group P2(1)/a, with a = 23.743(3) A, b = 9.7522(5) A, c = 27.731(2) A, beta = 114.580(10) degrees, and Z = 4. Compound 2 crystallizes in the orthorhombic space group Pbcn, with a = 23.700(5) A, b = 25.162(5) A, c = 9.693(5) A, and Z = 4. The structures of 1 and 2 are made up of uncoordinated perchlorate anions and malonate-bridged zigzag copper(II) chains grouped in an isosceles triangle running parallel to the b (1) and c (2) axes. These chains are built by a [Cu(bpy)(mal)(H2O)] unit acting as bis-monodentate ligand toward two [Cu(bpy)(H2O)] adjacent units through its OCCCO skeleton in an anti-anti conformation, whereas the OCO carboxylate bridges exhibit the anti-syn conformation. Compounds 1 and 2 contain four crystallographically independent copper(II) atoms, but the environment of all of them is distorted square pyramidal: the axial position is occupied by a water molecule, whereas the equatorial plane is formed by a chelating bpy and either a bidentate malonate or two carboxylate oxygens from two malonate groups. The equatorial Cu-O(mal) (1.911(4)-1.978(4) (1) and 1.897(5)-1.991(4) A (2)) and Cu-N(bpy) (1.983(4)-2.008(5) (1) and 1.971(6)-2.007(6) A (2)) bonds are somewhat shorter than the axial Cu-O(w) one (2.257(5)-2.524(5) (1) and 2.236(5)-2.505(6) A (2)). The angles subtended at the copper atom by the chelating bpy vary in the ranges 80.9(2)-81.8(2) degrees (1) and 80.4(2)-82.1(2) degrees (2), values which are somewhat smaller than those of the chelating malonate (80.4(2)-82.1(2) degrees (1) and 93.0(2)-93.6(2) degrees (2)). The intrachain copper-copper separations through the OCCCO fragment are 8.227(1) (1) and 8.206(2) A (2), whereas those through the OCO bridging unit are 4.579(1)-5.043(1) (1) and 4.572(2)-5.040(2) A (2). The magnetic behavior of 1 and 2 in the temperature range 2.0-290 K is very close, and it corresponds to an overall ferromagnetic coupling, the chi MT versus T curve exhibiting a maximum at 18 K. The analysis of the magnetic data through a numerical expression derived for the real topology of 1 and 2, that is, chains of isosceles triangles with two intrachain exchange pathways J1 (exchange coupling through the OCO carboxylate) and J2 (exchange coupling through the OCCCO malonate), indicates the occurrence of ferro- (J1 = +4.6 cm-1) and antiferromagnetic couplings (J2 = -4.2 cm-1). The magnetic coupling through these exchange pathways is further analyzed and substantiated by density functional theory calculations on a malonate-bridged trinuclear copper(II) model system.
