Metal-Organic Frameworks with Hexakis(4-carboxyphenyl)benzene: Extensions to Reticular Chemistry and Introducing...

Nine metal-organic frameworks have been prepared with the hexagon-shaped linker 1,2,3,4,5,6-hexakis(4-carboxyphenyl)benzene (H₆cpb) by solvothermal reactions in dimethylformamide (dmf) or dimethylacetamide (dmac) with acetic acid or formic acid as modulators: [Bi₂(cpb)(acetato)₂(dmf)₂]·2dmf CTH-6 forms a rtl-net; 2(H₂NMe₂)[Cu₂(cpb)] CTH-7 forms a kgd-net; [Fe₄(cpb)(acetato)₂(dmf)₄] CTH-8 and [Co₄(cpb)(acetato)₂(dmf)₄] CTH-9 are isostructural and form yav-nets; 2(HNEt₃)[Fe₂(cpb)] CTH-10 and the two polymorphs of 2(H₂NMe₂)[Zn₂(cpb)]·1.5dmac, Zn-MOF-888 and CTH-11, show kgd-nets; [Cu₂(cpb)(acetato)₂(dmf)₂]·2dmf, CTH-12, forms a mixed coordination and hydrogen-bonded sql-net; and 2(H₂NMe₂)[Zn₂(cpb)] CTH-13, a similarly mixed yav-net. Surface area values (Brunauer-Emmett-Teller, BET) range from 34 m² g^-1 for CTH-12 to 303 m² g^-1 for CTH-9 for samples activated at 120 °C in dynamic vacuum. All compounds show normal (10-fold higher) molar CO₂ versus N₂ uptake at 298 K, except the 19-fold CO₂ uptake for CTH-12 containing Cu(II) dinuclear paddle-wheels. We also show how perfect hexagons and triangles can combine to a new 3D topology laf, a model of which gave us the idea of foldable network topologies, as the laf-net can fold into a 2D form while retaining the local geometry around each vertex. Other foldable nets identified are cds, cds-a, ths, sqc163, clh, jem, and tfc covering the basic polygons and their combinations. The impact of this concept on "breathing" MOFs is discussed. I₂ sorption, both from gas phase and from MeOH solution, into CTH-7 were studied by time of flight secondary ion mass spectrometry (ToF-SIMS) on dried crystals. I₂ was shown to have penetrated the crystals, as layers were consecutively peeled off by the ion beam. We suggest ToF-SIMS to be a method for studying sorption depth profiles of MOFs.