Dohyun Moon

Luminescent Li-Based Metal–Organic Framework Tailored for the Selective Detection of Explosive Nitroaromatic Compounds: Direct Observation of Interaction Sites

A luminescent lithium metal-organic framework (MOF) is constructed from the solvothermal reaction of Li(+) and a well-designed organic ligand, bis(4-carboxyphenyl)-N-methylamine (H(2)CPMA). A Li-based MOF can detect an explosive aromatic compound containing nitro groups as an explosophore, by showing a dramatic color change with concurrent luminescence quenching in the solid state. The detection sites are proven directly through single-crystal-to-single-crystal transformations, which show strong interactions between the aromatic rings of the electron-rich CPMA(2-) molecules and the electron-deficient nitrobenzene.

Diamine-functionalized metal–organic framework: exceptionally high CO2 capacities from ambient air and flue gas, ultrafast CO2 uptake rate, and adsorption mechanism

A framework en-Mg2(dobpdc) (1-en; en = ethylenediamine) functionalized with the primary amine en was prepared via postmodification. From synchrotron PXRD data, it is revealed that the cell parameters change upon grafting of en and CO2 uptake. The adsorbed CO2 amount of 1-en is 4.57 mmol g−1 (16.7 wt%) at 25 °C and 1 bar and decreases to 3.00 mmol g−1 (11.7 wt%) at 150 °C. Noticeably, 1-en shows a significant CO2 uptake (3.62 mmol g−1, 13.7 wt%) at 0.15 bar, which is comparable to the CO2 partial pressure of a post-combustion flue gas. The CO2 capacity of 1-en at 0.39 mbar, close to atmospheric CO2 concentration, is 2.83 mmol g−1 (11.1 wt%), which marks the highest amount among MOFs. The isosteric heat of adsorption (−Qst) of 1-en in CO2 capture corresponds to 49–51 kJ mol−1, which is supported by DFT calculations (−52.8 kJ mol−1). These results suggest that the adsorption of CO2 onto the free amines of en leads to the formation of a carbamic acid. Adsorption–desorption cyclings of CO2 at the real dilute concentrations of air and flue gas are established with almost retaining CO2 capacities, which could provide superior potential for practical application in CO2 capture. The adsorption rate of CO2 in 1-en exceeds that in some other tested porous materials. The recyclability in CO2 uptake for 1-en is maintained even after exposure to humidity.

Characterization of Vinylgold Intermediates: Gold‐Mediated Cyclization of Acetylenic Amides

Vinylgold intermediates involved in various gold-catalyzedreactions are known to undergo proto-deauration in thepresence of a proton source. The unexpected result drew ourattention on the chemistry of vinylgold intermediatesinvolved and thus prompted us to investigate the gold-mediated cyclization in detail with simple substrates, N-(propargyl)benzamides. Described herein is identification ofthe vinylgold(III) intermediates involved and their reactionpathways, all of which expands our present understanding onthe vinylgold intermediates.The treatment of N-(propargyl)benzamide (1) with anequimolar amount of AuCl

CO2 capture from humid flue gases and humid atmosphere using a microporous coppersilicate

Grabbing CO2 from wet gas streams It is a challenge to extract CO2 from typical gas streams, such as the flue gas from a power plant. This is because any water in the stream tends to prevent CO2 absorption and may also degrade the absorbing material. Datta et al. developed a microporous copper silicate that avoids these problems. Most other materials have sites that absorb both water and CO2 at the same sites, and in that fight, the water tends to win. Although their material still absorbs water, it has separate sites for the CO2 absorption. It also shows good stability despite the absorbed water and can be reused. Science, this issue p. 302 A material with different sites for CO2 and water absorption can extract CO2 from moist gas streams. Capturing CO2 from humid flue gases and atmosphere with porous materials remains costly because prior dehydration of the gases is required. A large number of microporous materials with physical adsorption capacity have been developed as CO2-capturing materials. However, most of them suffer from CO2 sorption capacity reduction or structure decomposition that is caused by co-adsorbed H2O when exposed to humid flue gases and atmosphere. We report a highly stable microporous coppersilicate. It has H2O-specific and CO2-specific adsorption sites but does not have H2O/CO2-sharing sites. Therefore, it readily adsorbs both H2O and CO2 from the humid flue gases and atmosphere, but the adsorbing H2O does not interfere with the adsorption of CO2. It is also highly stable after adsorption of H2O and CO2 because it was synthesized hydrothermally.

High mobility organic single crystal transistors based on soluble triisopropylsilylethynyl anthracene derivatives

A series of new anthracene based semiconductors are designed and synthesized. By substituting appropriate acenes at the 2,6-positions of triisopropylsilylethynyl anthracene (NMR, IR, DSC and TGA spectra and crystallographic information of TIPSAntBT and TIPSAntNa), two different derivatives were prepared. Especially, TIPSAntNa (naphthalene as a side group) showed superior performance when it was used as channel material. A hole mobility as high as 3.7 cm2 V−1 s−1 was obtained from single crystal OFETs. To elucidate the origin of this high performance, we carried out comparative studies to investigate the direct relationship between the molecular-packing parameters and the field-effect mobility in single-crystal OFETs because the performance of such single-crystal OFETs is not affected by defects and grain boundaries. Comparing TIPSAN single crystal OFETs having four different acene derivatives, and applying the concept of molecular overlap ratio along the long/short axis, we could show that the effective π-stacking area dominantly determines the field-effect mobility of π-stacked materials. In the case of TIPSAntNa, a large π-stacking area and a small π-stacking distance enabled the highest field-effect mobility.

Novel 48-membered hexadecanuclear and 60-membered icosanuclear manganese metallamacrocycles.

Either an S 8 symmetrical 48-membered hexadecanuclear or an S 10 symmetrical 60-membered icosanuclear manganese metallamacrocycle was self-assembled using a manganese ion and a ditopic pentadentate ligand. This was either N-4-phenylbenzoylsalicylhydrazide (H 3pbshz) containing a rigid rod-shaped, bulky biphenyl residue as a terminal N-acyl group or N-3,3-diphenylpropionylsalicylhydrazide (H 3dppshz) containing a flexible beta-branched N-acyl group, but with two sterically bulky phenyl residues at the Cbeta position. The backbone of these metal-organic assemblies is a repeating unit consisting of a -[Mn-N-N-] link that extends to complete either the 48-membered cyclic structure involving 16 manganese(III) centers and 16 ditopic linker ligands or the 60-membered cyclic structure involving 20 manganese(III) centers and 20 ditopic linker ligands (depending on the ligand used). Even though the nuclearity of the metallamacrocycles was different, the successive manganese centers were in the same chiral sequence, ...(LambdaLambdaDeltaDelta)(LambdaLambdaDeltaDelta)....

Reversible fluorescence switching and topochemical conversion in an organic AEE material: polymorphism, defection and nanofabrication mediated fluorescence tuning

2-(4-(Diphenylamino)-2-methoxybenzylidene) malononitrile (DPAMBM), an organic aggregation enhanced emission material, showed an external stimulus mediated reversible phase change (crystalline to amorphous) and fluorescence switching as well as multiple factor mediated fluorescence tuning in the solid state. Polymorphic crystals obtained from CH3CN (DPAMBM-1) and CH3OH (DPAMBM-2) exhibited fluorescence at 588 nm and 538 nm, respectively. Single crystal analysis showed a slightly twisted molecular conformation between aminophenyl (donor) and malononitrile (acceptor) and the molecules are well separated in the crystal lattice. Whereas linear molecular conformation and strong intermolecular interaction with anti-parallel dipole arrangement were observed in DPAMBM-2. Slight breaking and strong grinding of DPAMBM-1 crystals showed blue shifting of fluorescence to 571 nm and 562 nm, respectively. Interestingly, annealing/solvent vapor exposure further blue shifts the fluorescence to 545 nm and converts the ground powder to DPAMBM-2. Strong grinding of DPAMBM-2 red shifted the fluorescence to 562 nm and annealing/vapor exposure switched back to 545 nm. DPAMBM-2 was converted to DPAMBM-1 by annealing at 120 °C that tuned the fluorescence from 538 nm to 572 nm and mechanical grinding and annealing further blue shifts the fluorescence to 545 nm. Nanofabrication of DPAMBM also showed fluorescence tuning from 562 nm to 536 nm due to morphological changes. Thus DPAMBM showed a rare combination of gradual fluorescence tuning from 588 nm to 536 nm and an external stimulus controlled phase change with fluorescence switching between 545 nm and 562 nm.

Porphyrin Boxes: Rationally Designed Porous Organic Cages

The porphyrin boxes (PB-1 and PB-2), which are rationally designed porous organic cages with a large cavity using well-defined and rigid 3-connected triangular and 4-connected square shaped building units are reported. PB-1 has a cavity as large as 1.95 nm in diameter and shows high chemical stability in a broad pH range (4.8 to 13) in aqueous media. The crystalline nature as well as cavity structure of the shape-persistent organic cage crystals were intact even after complete removal of guest molecules, leading to one of the highest surface areas (1370 m(2) g(-1)) among the known porous organic molecular solids. The size of the cavities and windows of the porous organic cages can be modulated using different sized building units while maintaining the topology of the cages, as illustrated with PB-2. Interestingly, PB-2 crystals showed unusual N2 sorption isotherms as well as high selectivity for CO2 over N2 and CH4 (201 and 47.9, respectively at 273 K at 1 bar).

Steric control of the nuclearity of metallamacrocycles: formation of a hexanuclear gallium metalladiazamacrocycle and a hexadecanuclear manganese metalladiazamacrocycle†‡

An S6-symmetric hexanuclear gallium metalladiazamacrocycle, [Ga(III)(6)L2(6)S6] with a -(lamda delta)(lamda delta)-chiral sequence and an S-symmetric hexadecanuclear manganese metalladiazamacrocycle, [Mn(III)(16)L2(16)S16] with a -(lamda lamda delta delta)(lamda lamda delta delta)-chiral sequence were prepared using the same N2-trans-cinnamoyl-2-hydroxy-3-naphthoylhydrazide (H3L2) as a bridging pentadentate ligand between the metal centers for the formation of a macrocyclic system.

Exploration of Gate-Opening and Breathing Phenomena in a Tailored Flexible Metal–Organic Framework

Flexible metal-organic frameworks (MOFs) show the structural transition phenomena, gate opening and breathing, upon the input of external stimuli. These phenomena have significant implications in their adsorptive applications. In this work, we demonstrate the direct capture of these gate-opening and breathing phenomena, triggered by CO2 molecules, in a well-designed flexible MOF composed of rotational sites and molecular gates. Combining X-ray single crystallographic data of a flexible MOF during gate opening/closing and breathing with in situ X-ray powder diffraction results uncovered the origin of this flexibility. Furthermore, computational studies revealed the specific sites required to open these gates by interaction with CO2 molecules.