Synthesis, Characterization, and Adsorption Studies of Nickel(II), Zinc(II), and Magnesium(II) Coordination Frameworks of BTTB

Three porous metal organic frameworks {[Ni(H2BTTB)center dot(H2O)(2)]center dot(DIOX)(2)}(n) (1), {[Zn(H2BTTB)]center dot(DEF)(3)center dot(H2O)(2)}(n) (2), and {[Mg(H2BTTB)center dot(C2H5OH)(2)]center dot(DEF)(4)}(n) (3) based on the 4,4',4 '',4'''-benzene-1,2,4,5-tetrayltetrabenzoic acid (H4BTTB) ligand have been synthesized under solvothermal conditions (DIOX = dioxane). These three MOFs show structural diversities: compound 1 is a two-dimensional (2D) grid layer, compound 2 is a 2-fold interpenetrated 3D framework with a pillared-layer structure, and compound 3 is a noninterpenetrated 3D framework with a (4, 4)-connected binodal net. Compound 1 and compound 2 have BET surface areas of 391 and 447 m(2)/g, respectively; however, the surface area of compound 3 cannot be experimentally determined. All three MOFs have a higher adsorption preference for CO2 over N-2 and CH4. Ideal adsorbed solution theory was used to estimate binary adsorption selectivities. Compound 2 shows the highest capacity for all three gases, whereas compound 1 shows the highest selectivity for CO2 over CH4 and N-2. Compound 1 exhibits a selectivity of similar to 30 for CO2 over N-2 in equimolar mixtures.