Solvent-induced secondary building unit (SBU) variations in a series of Cu(II) metal-organic frameworks derived from a bifunctional ligand

The role of auxiliary solvents in the formation of metal-organic frameworks (MOFs) has been studied for a series of copper-based framework systems. Herein we show the formation of three different 3D ordered frameworks with the formulae {[Cu-4(cpt)(4)Cl-4]center dot 2DMF center dot dioxane center dot 3H(2)O}(n) (1), {[Cu-8(cpt)(4)(Hcpt)(2)Cl-7-(mu(3)-OH)(2)(H2O)(4)]Cl-3 center dot 4CH(3)CN}(n) (2), and {[Cu-8(cpt)(4)Cl-4(mu(3)-OH)(2)(mu(4)-O)(2)]Cl-2 center dot 4H(2)O center dot 2CH(3)CN center dot 3MeOH}(n) (3) [Hcpt = 4-(4-carboxyphenyl)-1,2,4-triazole], respectively, from the same reaction mixture through varying auxiliary solvents of the medium. These MOFs were fully characterized by single-crystal X-ray diffraction, showing interesting secondary building unit (SBU) variations. The varied SBUs not only bring different framework architectures to these MOFs, but also affect their framework stability. Gas sorption studies of MOF3 reveal high CO2-N-2 selectivity at 298 K and 0.16 bar (a typical partial pressure of CO2 in an industrial flue gas). A high isosteric heat of adsorption (Q(st)) at zero loading (53 kJ mol(-1)) was also observed in MOF 3.