Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ...ultramicroporous material sql‐SIFSIX‐bpe‐Zn exhibits an induced fit binding mechanism when exposed to acetylene, C2H2. The resulting phase change affords exceptionally strong C2H2 binding that in turn enables highly selective C2H2/C2H4 and C2H2/CO2 separation demonstrated by dynamic breakthrough experiments. sql‐SIFSIX‐bpe‐Zn was observed to exhibit at least four phases: as‐synthesised (α); activated (β); and C2H2 induced phases (β′ and γ). sql‐SIFSIX‐bpe‐Zn‐β exhibited strong affinity for C2H2 at ambient conditions as demonstrated by benchmark isosteric heat of adsorption (Qst) of 67.5 kJ mol−1 validated through in situ pressure gradient differential scanning calorimetry (PG‐DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C2H2 induced fit transformation, binding positions and the nature of host‐guest and guest‐guest interactions.
We introduce the new flexible physisorbent sql‐SIFSIX‐bpe‐Zn and reveal that it exhibits an induced fit structural change that results in extraordinary affinity for C2H2 that in turn enables high selectivity for separation of C2H2 over C2H4 and CO2.
We report that linker ligand substitution involving just one atom induces a shape‐memory effect in a flexible coordination network. Specifically, whereas SIFSIX‐23‐Cu, Cu(SiF6)(L)2n, ...(L=1,4‐bis(1‐imidazolyl)benzene, SiF62−=SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX‐23‐CuN, Cu(SiF6)(LN)2n (LN=2,5‐bis(1‐imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO2. As‐synthesized SIFSIX‐23‐CuN, α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N2 (77 K), rather it reverted to α induced by CO2 at 195, 273 and 298 K. CO2 desorption resulted in α′, a shape‐memory phase which subsequently exhibited type‐I isotherms for N2 (77 K) and CO2 as well as strong performance for separation of CO2/N2 (15/85) at 298 K and 1 bar driven by strong binding (Qst=45–51 kJ/mol) and excellent CO2/N2 selectivity (up to 700). Interestingly, α′ reverted to β after re‐solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX‐23‐CuN.
Linker engineering of a flexible SiF62− (SIFSIX) pillared network via single atom substitution profoundly changes the sorption behavior and affords a kinetically stable shape‐memory material. The ‘memorized’ open phase efficiently purifies a CO2/N2 (15/85) mixture in a manner which would be infeasible for the nonporous variant.
C3 hydrocarbons (HCs), especially propylene and propane, are high‐volume products of the chemical industry as they are utilized for the production of fuels, polymers, and chemical commodities. Demand ...for C3 HCs as chemical building blocks is increasing but obtaining them in sufficient purity (>99.95%) for polymer and chemical processes requires economically and energetically costly methods such as cryogenic distillation. Adsorptive separations using porous coordination networks (PCNs) could offer an energy‐efficient alternative to current technologies for C3 HC purification because of the lower energy footprint of sorbent separations for recycling versus alternatives such as distillation, solvent extraction, and chemical transformation. In this review, we address how the structural modularity of porous PCNs makes them amenable to crystal engineering that in turn enables control over pore size, shape, and chemistry. We detail how control over pore structure has enabled PCN sorbents to offer benchmark performance for C3 separations thanks to several distinct mechanisms, each of which is highlighted. We also discuss the major challenges and opportunities that remain to be addressed before the commercial development of PCNs as advanced sorbents for C3 separation becomes viable.
The study of porous coordination networks (PCNs) for their ability to purify C3 hydrocarbons (HCs) represents a subject of growing interest thanks to the potential for reduction of the energy footprint of these high‐volume energy‐intensive separations. This review highlights recent advances in our understanding of sorbent‐sorbate binding in PCNs and how this has enabled the setting of new benchmarks for separation performance, setting the stage for further improvements.
Although crystal engineering strategies are generally well explored in the context of multicomponent crystals (cocrystals) formed by neutral coformers (molecular cocrystals), cocrystals comprised of ...one or more salts (ionic cocrystals, ICCs) are understudied. We herein address the design, preparation, and structural characterization of ICCs formed by phenolic moieties, a common group in natural products and drug molecules. Organic and inorganic bases were reacted with the following phenolic coformers: phenol, resorcinol, phloroglucinol, 4-methoxyphenol, and 4-isopropylphenol. Nine ICCs were crystallized, each of them sustained by the phenol–phenolate supramolecular heterosynthon (PhOH···PhO–). Such ICCs are of potential utility, and there are numerous examples of phenolic compounds that are biologically active, some of which suffer from low aqueous solubility. The propensity to form ICCs sustained by the PhOH···PhO– supramolecular heterosynthon was evaluated through a combination of Cambridge Structural Database (CSD) mining, structural characterization of nine novel ICCs, and calculation of interaction energies. Our analysis of these 9 ICCs and the 41 relevant entries archived in the CSD revealed that phenol groups can reliably form ICCs through charge-assisted PhOH···PhO– interactions. This conclusion is supported by hydrogen-bond strength calculations derived from CrystalExplorer that reveal the PhOH···PhO– interaction to be around 3 times stronger than the phenol–phenol hydrogen bond. The PhOH···PhO– supramolecular heterosynthon could therefore enable crystal engineering studies of a large number of phenolic pharmaceutical and nutraceutical compounds with their conjugate bases.
Closed-to-open structural transformations in flexible coordination networks are of potential utility in gas storage and separation. Herein, we report the first example of a flexible SiF6 2–-pillared ...square grid material, Cu(SiF6)(L)2 n (L = 1,4-bis(1-imidazolyl)benzene), SIFSIX-23-Cu. SIFSIX-23-Cu exhibits reversible switching between nonporous (β1) and several porous (α, γ1, γ2, and γ3) phases triggered by exposure to N2, CO2, or H2O. In addition, heating β1 to 433 K resulted in irreversible transformation to a closed polymorph, β2. Single-crystal X-ray diffraction studies revealed that the phase transformations are enabled by rotation and geometrical contortion of L. Density functional theory calculations indicated that L exhibits a low barrier to rotation (as low as 8 kJmol–1) and a rather flat energy surface. In situ neutron powder diffraction studies provided further insight into these sorbate-induced phase changes. SIFSIX-23-Cu combines stability in water for over a year, high CO2 uptake (ca. 216 cm3/g at 195 K), and good thermal stability.
We have demonstrated for the first time that isostructural homochiral metal-organic frameworks (MOFs) can be synthesized directly from chiral ligands and indirectly from achiral ligands via ...spontaneous resolution combined with cooperative chirality induction, respectively. Moreover, the usage of different ligands leads to distinct proton conduction behaviors.
In China, breast cancer is currently the most common malignancy and the sixth leading cause of cancer death in women. But, the characteristics of breast cancer in the whole population are not ...determined. The aim of this study was to perform a detailed study on pathologic characteristics of breast cancer representing the whole population in China during 1999–2008 and to compare the difference in invasive breast cancer between the Western and Chinese. We randomly collected 4,211 inpatient at seven hospitals in representative geographical regions of China during 1999–2008. All the hospitals had the ability of comprehensive cancer treatment. The pathologic characters including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status were surveyed. The shift of pathologic characters was evaluated and the data from China were also compared with those of the Western, both using Chi‐square test. We found as follow. (i) The median age of the patients was 48 years and showed the similar characters of Asia. (ii) Breast cancer in China showed more invasive ductal carcinoma with larger tumor size, later stage, lower ER and PR expression and higher HER2 overexpression than those in the Western (p < 0.001). (iii) Both tumor size and stage at diagnosis decreased year by year (p < 0.001). Breast cancer in China showed more aggressive behavior than those in western countries, although tumor size and stage at diagnosis decreased by year during 1999–2008. We addressed the urgent needs for employ race‐specific breast cancer screen, diagnosis methods, and therapeutic models in China.
The first polyoxometalate-based metal-organic nanotube constructed via covalent bonds has been synthesized. POM anions stick the metal-organic nanotubes to build 3D nanotubular arrays. The stability, ...magnetic and proton conducting properties are investigated.
A 4
.6
.8 topology hybrid ultramicroporous material (HUM), {Cu
F(SiF
)(L)
·G}
, (L = 4,4'-bisimidazolylbiphenyl, G = guest molecules), 1, formed by cross-linking interpenetrated 3D four-connected ...CdSO
-type nets with hexafluorosilicate anions is synthesized and evaluated in the context of gas sorption and separation herein. 1 is the first HUM functionalized with two different types of fluorinated sites (SiF
and F
anions) lining along the pore surface. The optimal pore size (≈5 Å) combining mixed and high-density electronegative fluorinated sites enable 1 to preferentially adsorb C
H
over CO
and C
H
by hydrogen bonding interactions with a high C
H
isosteric heat of adsorption (Q
) of ≈42.3 kJ mol
at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for C
H
/CO
and C
H
/C
H
that surpasses many well-known sorbents. Dynamic breakthrough experiments are conducted to confirm the practical separation capability of 1, which reveal an impressive separation factor of 6.1 for equimolar C
H
/CO
mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of C
H
stems from the chelating fix of C
H
between SiF
anion and coordinated F
anion.
A 44.610.8 topology hybrid ultramicroporous material (HUM), {Cu1.5F(SiF6)(L)2.5·G}n, (L = 4,4'-bisimidazolylbiphenyl, G = guest molecules), 1, formed by cross-linking interpenetrated 3D ...four-connected CdSO4-type nets with hexafluorosilicate anions is synthesized and evaluated in the context of gas sorption and separation herein. 1 is the first HUM functionalized with two different types of fluorinated sites (SiF6 2- and F- anions) lining along the pore surface. The optimal pore size (≈5 Å) combining mixed and high-density electronegative fluorinated sites enable 1 to preferentially adsorb C2H2 over CO2 and C2H4 by hydrogen bonding interactions with a high C2H2 isosteric heat of adsorption (Qst) of ≈42.3 kJ mol-1 at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for C2H2/CO2 and C2H2/C2H4 that surpasses many well-known sorbents. Dynamic breakthrough experiments are conducted to confirm the practical separation capability of 1, which reveal an impressive separation factor of 6.1 for equimolar C2H2/CO2 mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of C2H2 stems from the chelating fix of C2H2 between SiF6 2- anion and coordinated F- anion.
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