The defined synthesis of OMS in MOFs is the basis for targeted functionalization through grafting, the coordination of weakly binding species and increased (supramolecular) interactions with guest molecules.

New acetylenedicarboxylate (ADC) and chlorofumarate (Fum-Cl) based hafnium-metal–organic frameworks have been synthesized by alternatively reacting acetylenedicarboxylic acid in DMF or water with appropriate hafnium salt, in the presence of acetic acid modulator. The two materials of respective ideal formulas [Hf6O4(OH)4(ADC)6] (Hf-HHU-1) and [Hf6O4(OH)4(Fum-Cl)6] (Hf-HHU-2) have been structurally characterized by powder X-ray diffraction to be UiO-66 isostructural, consisting of octahedral [Hf6O4(OH)4]12+ secondary building units each connected to other units by 12 ADC or Fum-Cl linkers into a microporous network with fcu topology. This structure was confirmed by Rietveld refinement. Hf-HHU-2 is formed by in situ hydrochlorination of acetylenedicarboxylic acid to chlorofumarate. Its presence has been determined by combined Raman spectroscopy, solid-state NMR, scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopies. Hf-HHU-1 and Hf-HHU-2 exhibit very high hydrophilicity as revealed by their water sorption profiles, meanwhile Hf-HHU-2 adsorbs CO2 with an isosteric heat of 39 kJ mol–1. Hf-HHU-2 also adsorbs molecular iodine vapor exclusively as polyiodide anions due to grafted chloro-functions on the pores surface. It has been observed that defective nanodomains with reo tolopology can be introduced in the structure of Hf-HHU-2 by variation of the linker to metal-salt molar ratio.

The report is the first broader evaluation of the gas sorption properties of CAU-23 for the adsorptives CO 2 , H 2 , CH 4 , and SO 2 . CAU-23 is of intermediate porosity among Al-MOFs with specific BET surface areas of the order of MIL-100 > MIL-53 > CAU-23 > MIL-160 > MIL-53-TDC > Alfum > CAU-10-H and total pore volumes of the order of MIL-100 > MIL-53 > CAU-23 > Alfum = MIL-160 > MIL-53-TDC > CAU-10-H. CO 2 uptake (3.97 mmol g À 1 , 293 K) and H 2 uptake (10.25 mmol g À 1 , 77 K) of CAU-23 are second in the series and only slightly smaller than for MIL-160. The CH 4 uptake of CAU-23 (0.89 mmol g À 1 , 293 K) is unremarkable in comparison with the other Al-MOFs. The SO 2 uptake (8.4 mmol g À 1 , 293 K) follows the porosity and higher SO 2 uptakes were only observed for MIL-53 and MIL-100. CAU-23 is one of the best Al-MOFs for high-pressure sorption of CO 2 , with an uptake of 33 wt.-% at 20 bar, 293 K. Gas sorption measurements at two different temperatures gave near zero-coverage enthalpy of adsorptions, ~Hads 0 for CO 2 of À 22 kJ mol À 1 and of SO 2 for À 38 kJ mol À 1 which is at the low end of the other Al-MOFs (À 22 to À 39 kJ mol À 1 for CO 2 ; À 41 to À 51 kJ mol À 1 for SO 2 ), yet ~Hads increases for CAU-23 with CO 2 and SO 2 to À 25 and À 57 kJ mol À 1 , respectively. For CO 2 /CH 4 and SO 2 /CO 2 separation, ideal adsorbed solution theory (IAST) predicted gas selectivities of 5 and 27-50 (depending on molar ratio and model), respectively, in line with 4.5-6.3 and 17-50, respectively, with most of the other Al-MOFs, where only MIL-53-TDC with 83 and MIL-160 with 126 gave a higher SO 2 /CO 2 selectivity at a molar ratio of 0.5.

The prototypal [M2(EtBCP)2(DABCO)0.5] MOFs, compliant with isoreticular expansion in two-dimensions, show flexibility manifested by a two-step CO2 adsorption isotherm, which might be associated to the “lever-action” of the metal-phosphonate moieties.

The two‐dimensional (2D) cobalt‐carboxylate framework of the hxl type with the formula [Co3(bdc)3(DMA)3]·DMA was synthesized in a mixture of the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate [BMIm][BF4], HBF4 and N,N‐dimethylacetamide (DMA) via solvothermal reaction. The structure of [Co3(bdc)3(DMA)3]·DMA (bdc2– = benzene‐1,4‐dicarboxylate) consists of an hourglass trinuclear secondary building unit (SBU) with the first octahedral (oct)‐octahedral and square‐pyramidal (sq‐pyr) coordinated cobalt atoms in the sequence Cooct–Cooct–Cosq‐pyr with terminally coordinated DMA molecules. These SBUs are bridged by six bdc2– ligands into a two‐dimensional layered structure.