Minhak Oh

A Twofold Interpenetrating Porous Metal−Organic Framework with High Hydrothermal Stability: Structure and Gas Sorption Behavior

A twofold interpenetrating polyhedron-based metal-organic framework with high hydrothermal stability was prepared using a rigid and bent C(2)-symmetric ligand containing two 3,5-benzenedicarboxylate units, which have large surface area and high uptake capacities for various gas molecules.

A two-fold interpenetrated (3,6)-connected metal–organic framework with rutile topology showing a large solvent cavity

A two-fold interpenetrated metal–organic framework (MOF), [(Zn4O)2L4(DMF)2(H2O)3], was prepared using the tritopic ligand 4,4′,4′′-[1,3,5-benzenetriyltris(carbonylimino)]trisbenzoic acid (H3L) and zinc nitrate. The MOF, based on the hexatopic tetranuclear Zn4O(COO)6 secondary building unit, has a (3,6)-connected network with an rtl topology and a large solvent cavity.

Hybrid bimetallic metal-organic frameworks: modulation of the framework stability and ultralarge CO2 uptake capacity.

A series of isostructural hybrid bimetallic metal-organic frameworks (MOFs), Ni(x)M(1-x)-ITHDs [M = Zn(II), Co(II)], have been prepared via a conventional solvothermal reaction in the presence of varying mole ratios of Ni(II)/Zn(II) or Ni(II)/Co(II) mixed metal ions. While a critical amount of the doped Ni(II) ion (more than ≈0.2 mol fraction) is needed to have any enhancement of the framework stability of the hybrid bimetallic NixZn1-x-ITHDs, even a very small amount of the doped Ni(II) ion (≈0.1 mol fraction) produced a full enhancement of the framework stability of the hybrid bimetallic Ni(x)Co(1-x)-ITHDs. The highly porous and rigid Ni(x)Co(1-x)-ITHDs activated via a conventional vacuum drying process shows a Brunauer-Emmett-Teller specific surface area of 5370 m(2) g(-1), which is comparable to that of pure Ni-ITHD. The CO2 uptake capacities of Ni-ITHD and Ni(0.11)Co(0.89)-ITHD (2.79 and 2.71 g g(-1), respectively) at 1 bar and 195 K are larger than those of any other reported MOFs under similar conditions and the excess CO2 uptake capacity at 40 bar and 295 K (≈1.50 g g(-1)) is comparable to those of other MOFs, which are activated via the supercritical carbon dioxide drying process, with similar pore volumes.

Crystal-to-Crystal Transformations of a Series of Isostructural Metal− Organic Frameworks with Different Sizes of Ligated Solvent Molecules

Isostructural 3D metal-organic frameworks (MOFs) [Zn2(BTC)(NO3)S3] [where BTC = 1,3,5-benzenetricarboxylate; S = EtOH (1), DMF (2), DMA (3), or DEF (4)] of a 3-connected srs net topology have been prepared in the presence of serine as a template. The MOFs show different framework stabilities depending on the sizes of the ligated solvent molecules and undergo a crystal-to-crystal transformation at ambient conditions into a 1D chain structure either directly or via different types of intermediates depending on the ligated solvent molecules and the sample handling conditions. A single crystal of the MOF with the ligated DMF molecules, [Zn2(BTC)(NO3)(DMF)3] (2), is stable in Mg(II)- and Co(II)-DMF solutions; however, it transforms into a single particle-like microcrystalline aggregate of Cu-HKUST-1 in a Cu(II)-DMF solution.

A microporous metal–organic framework constructed from a 1D column made of linear trinuclear manganese secondary building units

A metal–organic framework (MOF) was prepared based on a 1D column made of a linear trinuclear manganese cluster as a secondary building unit (SBU), where the SBU is connected to two adjacent SBUs by carboxylates to form a 1D column and the column is further connected to four adjacent 1D columns via the SBUs to form a microporous MOF of pcu network topology.

An unprecedented twofold interpenetrated layered metal–organic framework with a MoS2-H topology

An unprecedented twofold interpenetrated layered metal–organic framework with a two-dimensional 3,6-connected net topology has been prepared using a tricarboxylic acid as a 3-connected node and a Zn4O(COO)6 cluster as a 6-connected node, where the ligand flexibility and the combination of π–π stacking and hydrogen bonding interactions render the 6-connected node into a topological trigonal prismatic node.

Isoreticular MOFs based on a rhombic dodecahedral MOP as a tertiary building unit

The solvothermal reactions of a Zn(II) ion with ligands containing two 1,3-benzene dicarboxylate residues linked via bent organic linkers with different flexibilities resulted in the isoreticular metal–organic frameworks (MOFs) PMOF-4 and PMOF-5 based on a rhombic dodecahedral metal–organic polyhedron (MOP) as a tertiary building unit (TBU). The rhombic dodecahedral MOP was built using six [Zn2(COO)4] clusters as a 4-c secondary building unit (SBU) and eight [Zn2(COO)3] clusters as a 3-c SBU. The network of the isoreticular MOFs based on the rhombic dodecahedral Zn–MOP is a 3,3,4-c net with a zjz topology, which is different from those of similar MOFs, PMOF-3 and PCN-12, based on a cuboctahedral Cu–MOP as a 24-c TBU. However, both 24-c TBUs in all MOFs were quadruply interlinked to six neighboring TBUs to form the same underlying pcu topology.

TiO2 Composites for Efficient Poly(3-thiophene acetic acid) Sensitized Solar Cells

The effect of TiO 2 mesoporous structures sensitized with poly(3-thiophene acetic acid) (PTAA) on the photovoltaic performance was investigated. In contrast to conventional Ru-complex dye-sensitized solar cells (DSCs), the cell efficiency (η) of PTAA-sensitized solar cells exhibited strong dependence on the Ti0 2 pore structures. Incorporation of up to 40 wt % large TiO 2 nanoparticles (L-Ti0 2 ) into small TiO 2 nanoparticles (S-TiO 2 ) increased η, in spite of a reduction in dye loading due to a decrease in surface area. The highest η of 2.36 ± 0.04% was obtained for a TiO 2 film comprised of S-TiO 2 (60 wt %) and L-TiO 2 (40 wt %). Electrochemical impedance measurements suggested that the 25% increase in η for the DSC comprised of 40 wt % L-Ti02 resulted not from rapid diffusion of the redox electrolyte through the larger pores, but instead was due to the higher electron density in the conduction band of TiO 2 . It was inferred, therefore, that the highest η obtained for the DSC comprised of 40 wt % L-TiO 2 was due to the high degree of anchoring of COOH groups. This inference was further confirmed by obtaining an η of 2.92 ± 0.06%, the highest η ever reported for a polymer-dye based DSC, using a low-molecular weight PTAA sensitizer.