The Complexity of Comparative Adsorption of C6 Hydrocarbons (Benzene, Cyclohexane, n-Hexane) at Metal-Organic Frameworks.

The relatively stable MOFs Alfum, MIL-160, DUT-4, DUT-5, MIL-53-TDC, MIL-53, UiO-66, UiO-66-NH2, UiO-66(F)4, UiO-67, DUT-67, NH2-MIL-125, MIL-125, MIL-101(Cr), ZIF-8, ZIF-11 and ZIF-7 were studied for their C6 sorption properties. An understanding of the uptake of the larger C6 molecules cannot simply be achieved with surface area and pore volume (from N2 sorption) but involves the complex micropore structure of the MOF. The maximum adsorption capacity at p p0-1 = 0.9 was shown by DUT-4 for benzene, MIL-101(Cr) for cyclohexane and DUT-5 for n-hexane. In the low-pressure range from p p0-1 = 0.1 down to 0.05 the highest benzene uptake is given by DUT-5, DUT-67/UiO-67 and MIL-101(Cr), for cyclohexane and n-hexane by DUT-5, UiO-67 and MIL-101(Cr). The highest uptake capacity at p p0-1 = 0.02 was seen with MIL-53 for benzene, MIL-125 for cyclohexane and DUT-5 for n-hexane. DUT-5 and MIL-101(Cr) are the MOFs with the widest pore window openings/cross sections but the low-pressure uptake seems to be controlled by a complex combination of ligand and pore-size effect. IAST selectivities between the three binary mixtures show a finely tuned and difficult to predict interplay of pore window size with (critical) adsorptive size and possibly a role of electrostatics through functional groups such as NH2.

Increase of network hydrophilicity from sql to lvt supramolecular isomers of Cu-MOFs with the bifunctional 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate linker.

The bifunctional linker 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid (H2mpba) was used for the synthesis of new (square lattice) sql 2D metal-organic frameworks (MOFs) [Cu(Hmpba)2]·L (L = DMF or ACN) in a solvent-mixture of dimethylformamide/water and acetonitrile/water. These sql 2D MOFs are supramolecular isomers of the lvt 3D network [Cu(Hmpba)2]·4MeOH·1H2O (lvt-MeOH) that was synthesized previously by Richardson and co-workers. All these frameworks are potentially porous structures with solvent molecules included in the channels of the as synthesized materials. After activation all three materials showed good CO2 adsorption capacity, demonstrated here for lvt-MeOH for the first time, with a saturation uptake of 113 cm3 g-1 (lvt-MeOH-act.), 111 cm3 g-1 (sql-DMF-act.) and 90 cm3 g-1 (sql-ACN-act.) at 195 K. The flexibility of the lvt-MeOH-act. network is evidenced by a gate-opening effect seen in the CO2 measurement at 195 K and under gravimetric high-pressure CO2 adsorption. According to the water and ethanol sorption measurements the new sql frameworks can be categorized as hydrophobic materials in contrast to the hydrophilic lvt framework. In the lvt-MeOH structure the crystal solvent can be replaced with water to yield the structurally authenticated water-only network lvt-H2O containing 3D arrays of S4-symmetric (H2O)20 clusters.

rtl-M-MOFs (M = Cu, Zn) with a T-shaped bifunctional pyrazole-isophthalate ligand showing flexibility and S-shaped Type F-IV sorption isotherms with high saturation uptakes for M = Cu.

Two new rtl-MOFs rtl-[Cu(HIsa-az-dmpz)] and rtl-[Zn(HIsa-az-dmpz)] have been synthesized by using the new bifunctional ligand 5-(4-(3,5-dimethyl-1H-pyrazolyl)azo)isophthalic acid (H3Isa-az-dmpz). Both frameworks are potentially porous structures with DMF molecules included in the channels of the as synthesized materials. The flexible MOF rtl-[Cu(HIsa-az-dmpz)] undergoes a reversible phase change into a closed form upon activation. Consequently, rtl-[Cu(HIsa-az-dmpz)] shows S-shaped Type F-IV adsorption profiles or a gate-opening effect at cryogenic temperatures with high saturation uptakes of 360 cm3 g-1 for N2 at 77 K and 310 cm3 g-1 for CO2 at 195 K. These profiles together with the reversibility could be reproduced upon repeated measurements on the same materials. The gravimetric high-pressure CO2 adsorption shows a gate-opening at ∼10 bar with an uptake of 332 mg g-1. rtl-[Zn(HIsa-az-dmpz)] undergoes an irreversible transformation into a non-porous phase upon activation.

Microwave-assisted dry-gel conversion-a new sustainable route for the rapid synthesis of metal-organic frameworks with solvent re-use.

Microwave-assisted dry-gel conversion (MW-DGC) combines the advantages of concentrated reactants in DGC with fast heating by microwave irradiation. This novel combination allows drastically decreasing the amount of solvent needed for synthesis and reaction times with the energy needed. Furthermore, MW-DGC allows for the recovery and re-use of the reaction solvent and thereby can significantly reduce the overall solvent waste in the syntheses of the four important MOFs MIL-100(Fe) (Basolite F300), UiO-66, MIL-140A and aluminium fumarate (Alfum, Basolite A520). All the MOF products obtained from MW-DGC showed satisfying yields, crystallinity and porosity in comparison with the industrial benchmarks Basolite F300 and Basolite A520. Moreover, MW-DGC also advantageously leads to a hierarchical micro-mesoporous Alfum material different to that from other synthesis methods.

Realizing the Potential of Acetylenedicarboxylate by Functionalization to Halofumarate in ZrIV Metal-Organic Frameworks.

A strategy was developed to obtain from acetylenedicarboxylic acid either an acetylenedicarboxylate-based ZrIV metal-organic framework (MOF) with fcu topology or a halo-functionalized-MOF-801 through in situ ligand hydrohalogenation. The new materials feature exceptionally high hydrophilicity and CO2 /H2 adsorption energetics. The acetylenedicarboxylate linker and its functionalizable triple-bond discloses its potential in the engineering of microporous materials with targeted properties.

Environmentally benign dry-gel conversions of Zr-based UiO metal-organic frameworks with high yield and the possibility of solvent re-use.

Herein we report an alternative synthesis method for Zr-based UiO metal-organic frameworks (MOFs), namely dry-gel conversion (DGC). It was possible to synthesize nano- to microsized UiO-66, UiO-66-NH2 and UiO-67 with high crystallinity, high surface area and increased yield using only one-sixth or less of the solvent volume compared to the solution synthesis on the same scale. Additionally, it is shown that solvent re-use is possible over at least five synthesis runs making the DGC method an ecological and extremely solvent-economical route to obtain Zr-based UiO-MOFs with reproducible results.

An analysis of the single-stage tympanoplasty with over-underlay grafting in tympanosclerosis.

OBJECTIVES: Our objective was to analyze the results of tympanosclerosis surgery using over-underlay tympanoplasty and to find out the effect of single-stage surgery on hearing results. MATERIALS AND METHODS: Forty-two patients who were operated on for tympanosclerosis between July 1998 and February 2002 were included in the study. These were one-stage tympanoplasties, because second-stage operations and revisions were not included. Operative records and audiograms of the patients were obtained. Of the patients, 48% had bilateral tympanosclerosis. In three (7.1%) of the patients, tympanosclerosis and cholesteatoma occurred concomitantly. The cog was present in eight (20%) of 40 mastoidectomies. Körner's septum was present in nine (22.5%) patients. The graft take rate was 95.2%. RESULTS: The pre- and postoperative air-bone gap values of the patients were not significantly different (p > 0.05). Thirty-three percent of the patients met the successful hearing criteria (air-bone gap <20 dB). However, 47% had an air-bone gap closure between 20 dB and 30 dB, whereas 20% had a gap of more than 30 dB. CONCLUSION: Single-stage surgery does not result in a satisfactory hearing improvement in most of the patients with tympanosclerosis. Only one third of the patients, most of whom had a mobile stapes, had satisfactory hearing results. Mobilization of a fixed stapes is not an effective option for hearing restoration in tympanosclerosis. Second-stage surgery for stapedectomy and placement of a prosthesis-like piston or total ossicular replacement prosthesis should be considered to obtain better hearing results in tympanosclerosis.