Thermally Robust 3-D Co-DpyDtolP-MOF with Hexagonally Oriented Micropores: Formation of Polyiodine Chains in a MOF Single Crystal

Abstract

A new porphyrin-based Co-MOF, [Co(DpyDtolP)] 6 ·12H 2 O (I) composed of DpyDtolP (5,15-di(4-pyridyl)-10,20-di(4-methylphenyl)porphyrin) was prepared in a high yield and structurally characterized by X-ray crystallography. DpyDtolP is a ditopic N-donor ligand with a large space or gap between the two pyridyl groups at the 5-and 15-positions of the porphyrin backbone. Unlike the pyridyl groups, the 4-tolyl groups in DpyDtolP could not be involved in coordination toward the metal ion. Nevertheless, the presence of these two 4-tolyl groups led to a new infinite three-dimensional framework: Co-MOF (I) with exceptionally high thermal stability at elevated temperature. The single crystals of I maintained their crystallinity even after vacuum drying at 250 °C. The resulting dried single crystals diffracted X-ray to give the same structural solution as the as-prepared crystals. The robust framework of I contained micropores that were periodically arranged in a hexagonal symmetry. While the evacuated I moderately sorbed N 2 at 77 K, it sorbed 142.8 cm 3 g -1 (6.37 mmol g -1 ) of CO 2 at 196 K. The CO 2 sorption isotherms exhibited a very clear step in both the adsorption and desorption branches. A slight hysteretic behavior was observed between the two branches. Furthermore, the crystal structure of CO 2 captured I (I_CO 2 ) revealed that the linear arrangement of the CO 2 molecules occupying the inside of micropores, thereby indicating the effective CO 2 capture by evacuated I.The evacuated I was also found to be ideal for the encapsulation of iodine molecules in cyclohexane to provide iodine-captured I (I_I 2 ), which was also characterized by X-ray crystallography. The linear arrangement of polyiodine chains in the micropores was observed, and a single crystal of I_I 2 exhibited electrically conducting behavior. The encapsulation amount of iodine was dependent on the crystal sizes of I. Additionally, the separately prepared microscale sample, micro-I, with a much reduced particle dimension than the bulk I exhibited an enhanced uptake of iodine under the same conditions.

Electrically Conductive Porous Metal–Organic Frameworks

“…[37] Weight analysis established that the I 2 loading is small, indicating that the charge transport is through the framework rather than through the I 2 guest molecules. [38,39] Thei ncrease in conductivity was ascribed to the partial oxidation of [Ni(pdt) 2 ]…”

“…[37] Weight analysis established that the I 2 loading is small, indicating that the charge transport is through the framework rather than through the I 2 guest molecules. [38,39] Thei ncrease in conductivity was ascribed to the partial oxidation of [Ni(pdt) 2 ] 2À by I 2 ,w hich provides loosely bound unpaired electrons as charge carriers.T hese studies demonstrate the benefit of using redox-active building units,w hich may allow for improved electrical conductivity via doping. Another strategy to realize through-bond charge transport is based on extended inorganic 1D chains or 2D sheets formed by the metal ions and the coordinating atoms of the organic ligands.T hese can be considered as dimensionally reduced versions of their bulk inorganic counterparts,such as metal oxides,m etal pnictides,a nd metal chalcogenides.T his strategy requires proper symmetry,s patial, and energy overlap of the orbitals of the metal ions and the coordinating atoms,t he energy overlap may be inferred from the relative electronegativities of the atoms involved.…”

Two Coordination Polymers and Their Silver(I)‐Doped Species: Synthesis, Characterization, and High Catalytic Activity for the Photodegradation of Various Organic Pollutants in Water

“…The average Cd–O bond length of 2.273(2) Å is shorter than that found in [Cd(tpcb) 0.5 (1,3‐bdc)] [2.337(4) Å; tpcb = tetrakis(4‐pyridyl)cyclobutane], but longer than that found in [Cd 3 L 2 (hbmb)(H 2 O) 2 ] · 2.5H 2 O {2.226 Å; hbmb = 1,1′‐(1,6‐hexane)bis(2‐methylbenzimidazole)} . In 2· 1.5H 2 O, the mean Co–N bond length [2.160(2) Å] is shorter than that observed in [Co(DpyDtolP)] 6 · 12H 2 O {2.259(2) Å; DpyDtolP = 5,15‐di(4‐pyridyl)‐10,20‐bis(4‐methylphenyl)porphyrin}, but longer than that found in [Co 2 (tipm)(1,3‐bdc) 2 ] · 0.5CH 3 CN {2.012(2) Å; tipm = tetrakis[4‐(1‐imidazolyl)phenyl]methane}. [10b] The average Co–O bond length of 2.016(19) Å is shorter than that of [Co 3 (btc) 2 (bimb) 2 ] · 4H 2 O [2.134(3) Å], but longer than that of [Co 2 (tipm)(1,3‐bdc) 2 ] · 0.5CH 3 CN [1.972(3) Å].…”

Face‐Capped M4L4 Tetrahedral Metal–Organic Cage: Iodine Capture and Release, Ion Exchange, and Electrical Conductivity

“…The weight of crystals increased up to 150 mg and reached equilibrium after 350 hours, amounting to 33.3 wt % total uptake (Figure a) with 7 iodine molecules in each cell unit. This value is among the highest values for the absorption of I 2 by MOCs and analogues such as porous MOFs . To confirm that the uptake of iodine occurs in the void of the crystal instead of on the surface, a control experiment was performed in which the ligand TABP and the crystal MOC‐19 were simultaneously exposed to iodine vapor under the same conditions (Figure S4).…”

“…On the other hand, the increasing risk of radioactive iodine in the waste of the nuclear industry is dangerous to the health of humans, and this waste is very difficult to deal with because of iodine's long half‐life time of 15.7 million years . Recently, the capture of iodine and its derivatives by metal–organic cages (MOCs), metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) has been vigorously investigated, showing fascinating prospects . For example, Zeng's group reported a highly stable MOF which exhibits kinetics of iodine loading and release similar to activated carbon .…”