Jeong Hwa Song

Superprotonic Conductivity of a UiO‐66 Framework Functionalized with Sulfonic Acid Groups by Facile Postsynthetic Oxidation

Facile postsynthetic oxidation of the thiol-laced UiO-66-type framework UiO-66(SH)2 enabled the generation of UiO-66(SO3 H)2 with sulfonic acid groups covalently linked to the backbone of the system. The oxidized material exhibited a superprotonic conductivity of 8.4×10(-2)  S cm(-1) at 80 °C and 90 % relative humidity, and long-term stability of the conductivity was observed. This level of conductivity exceeds that of any proton-conducting MOF reported to date and is equivalent to the conductivity of the most effective known electrolyte, Nafion.

Homodiamine-functionalized metal–organic frameworks with a MOF-74-type extended structure for superior selectivity of CO2 over N2

A porous Mg2(dondc) framework (H4dondc = 1,5-dioxido-2,6-naphthalenedicarboxylic acid) with open metal sites was prepared and functionalized with primary or secondary diamines (en = ethylenediamine, mmen = N,N′-dimethylethylenediamine, or ppz = piperazine). The CO2 adsorption was substantial under post-combustion flue gas conditions as compared to other reported metal–organic frameworks. Interestingly, the IR spectroscopic measurements demonstrated that the CO2 adsorption mechanism is based on the combination of physisorption and chemisorption. The CO2 adsorption capacity of 1-mmen was greater than that of 1-en and 1-ppz, which can likely be attributed to the basicity of the free amine groups tethered to the open coordination sites. Ultrahigh selectivity and superior dynamic separation of CO2 over N2 were evident in 1-ppz. Such exceptional CO2 uptake and CO2/N2 selectivity of diamine-functionalized materials hold potential promise for post-combustion CO2 capture applications.

Cost‐Effective, High‐Performance Porous‐Organic‐Polymer Conductors Functionalized with Sulfonic Acid Groups by Direct Postsynthetic Substitution

We demonstrate the facile microwave-assisted synthesis of a porous organic framework 1 and the sulfonated solid (1S) through postsubstitution. Remarkably, the conductivity of 1S showed an approximately 300-fold enhancement at 30 °C as compared to that of 1, and reached 7.72×10-2  S cm-1 at 80 °C and 90 % relative humidity. The superprotonic conductivity exceeds that observed for any conductive porous organic polymer reported to date. This material, which is cost-effective and scalable for mass production, also revealed long-term performance over more than 3 months without conductivity decay.

Switching of Slow Magnetic Relaxation Dynamics in Mononuclear Dysprosium(III) Compounds with Charge Density.

The symmetry around a Dy ion is recognized to be a crucial parameter dictating magnetization relaxation dynamics. We prepared two similar square-antiprismatic complexes, [Dy(LOMe)2(H2O)2](PF6) (1) and Dy(LOMe)2(NO3) (2), where LOMe = [CpCo{P(O)(O(CH3))2}3], including either two neutral water molecules (1) or an anionic nitrate ligand (2). We demonstrated that in this case relaxation dynamics is dramatically affected by the introduction of a charged ligand, stabilizing the easy axis of magnetization along the nitrate direction. We also showed that the application of either a direct-current field or chemical dilution effectively stops quantum tunneling in the ground state of 2, thereby increasing the relaxation time by over 3 orders of magnitude at 3.5 K.

Phase Transformation, Exceptional Quenching Efficiency, and Discriminative Recognition of Nitroaromatic Analytes in Hydrophobic, Nonporous Zn(II) Coordination Frameworks

Five-fold interpenetrated Zn(II) frameworks (1 and 2) have been prepared, and an irreversible phase transformation from 1 to 2 is found to occur through a dissolution-recrystallization process. Compound 1 exhibits the highest quenching efficiency (>96%) for nitrobenzene at 7 ppm among luminescent coordination polymers. Selective discrimination of nitroaromatic molecules including o-nitrophenol (o-NP), p-nitrophenol (p-NP), 2,4-dinitrophenol (DNP), and 2,4,6-trinitrophenol (TNP) is realized in 1 and 2 as a result of the fact that the framework-analyte interaction affords characteristic emission signals. This observation is the first case of a nonporous coordination framework for such discriminative detection. Notably, significant hydrophobicity is evident in the framework 1 because of its surface roughness, which accounts for the enhanced quenching ability.

A conductive porous organic polymer with superprotonic conductivity of a Nafion-type electrolyte

As potential solid electrolytes in fuel cells, porous organic polymers show compelling proton conductivities (up to ∼10−2 S cm−1), but even higher performance is required for real applications. In this work, we prepared a biphenyl-based organic polymeric framework of 1E with a larger surface area as an extended version of a phenyl-based polymer. The construction of the framework from C–C covalent bonds allows exceptional stability to be realized under the operating conditions of fuel cells. Successful post-synthetic modification of 1E afforded the sulfonated material 1ES. Notably, the conductivity of 1ES was ∼104 orders of magnitude greater than that of 1E at 30 °C and 90% relative humidity (RH). The conductivity of 1ES reached 1.59 × 10−1 S cm−1 at 80 °C and 90% RH, which is superior to those observed for any porous organic polymer conductors reported so far and even surpasses that of Nafion. This polymer, simply prepared and scalable for mass production, was stable at 80 °C and 90% RH for more than 4 months without conductivity loss.

Control of Interchain Antiferromagnetic Coupling in Porous Co(II)-Based Metal–Organic Frameworks by Tuning the Aromatic Linker Length: How Far Does Magnetic Interaction Propagate?

Three MOF-74-type Co(II) frameworks with one-dimensional hexagonal channels have been prepared. Co(II) spins in a chain are ferromagnetically coupled through carboxylate and phenoxide bridges. Interchain antiferromagnetic couplings via aromatic ring pathways operate over a Co-Co length shorter than ∼10.9 Å, resulting in a field-induced metamagnetic transition, while being absent over lengths longer than ∼14.7 Å.

Two- and three-dimensional Zn(II) coordination polymers constructed from mixed ligand systems: interpenetration, structural transformation and sensing behavior

Four Zn(II) coordination compounds (1–4) were prepared solvothermally by reacting Zn2+ ions and organic linkers of dim and carboxylic acid-based ligands. Two-dimensional structures (1 and 2), which are extended to three-dimensional frameworks with the assistance of multiple hydrogen bonding interactions, are formed by employing isophthalate-based organic ligands. 4-fold (3) and 3-fold (4) interpenetrations occur when organic linkers that have carboxylic acid groups located oppositely are used. Interestingly, the interpenetrating nets undergo phase transformation via two pathways involving solvent exchange/resolvation and solvent exchange/activation/resolvation, which reveals that the structures are flexible. Photoluminescence properties show the selective fluorescence quenching of 3 and 4 in nitrobenzene (NB) among the tested solvents. Such quenching is substantial even at low NB concentrations, which is associated with the existence of Lewis basic sites in the interpenetrating framework.