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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. [ABSTRACT FROM AUTHOR]

We report a systematic study on the possibility of forming mixed-linker metal–organic frameworks (MOFs) spanning between the aluminum MOFs CAU-23 and MIL-160 with their 2,5-thiophenedicarboxylate (TDC) and 2,5-furandicarboxylate (FDC) linkers, respectively. The planned synthesis of a mixed-linker MOF, combining TDC and FDC in the framework turned out to yield a rather largely intricate mixture of CAU-23 and MIL-160. This is due to the different opening angles of 150° for TDC versus 120° for FDC and the concomitant cis–trans versus cis-only OH-bridges in the infinite secondary building unit {Al(μ-OH)(O2C–)} chains. At the same time, the CAU-23 phase is accompanied by the polymorphic MIL-53-TDC phase with trans-only OH-bridges. The measurement of water vapor sorption isotherms was the method of choice to confirm the formation of mixed MOFs instead of mixed-linker phases. Thereby, the water sorption isotherms indicate the simultaneous formation of both MOF phases, albeit they do not exclude mixed-linker MOFs which may have formed at low levels of substitution. The differentiation via powder X-ray diffractometry (PXRD), IR-spectroscopy and nitrogen sorption was either not conclusive enough or impossible, due to similarities of the neat MOF phases. The synthesized MOF mixtures within the TDC : FDC ratios of 38 : 62 up to 82 : 18 exhibit two or three uptake steps in the water sorption isotherm, with the first two corresponding to an overlay from the individual water sorption isotherm of CAU-23 and MIL-160 and a third one from the additional MIL-53-TDC. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]