Strontium-coordination polymers based on tetrafluorophthalic and phthalic acids: mechanochemical synthesis, ab initio structures determination, and spectroscopic characterization

Abstract

Two strontium-based dicarboxylate systems [Sr(oBDC-F)(HO)] (1) and [{Sr(oBDC)(HO)}·HO] (2) were synthesized mechanochemically via milling of Sr(OH)·8HO with tetrafluorophthalic acid (HoBDC-F) or phthalic acid (HoBDC), respectively. The new structures were determined ab initio from the powder X-ray diffraction (PXRD) data. Both compounds 1 and 2 crystallize in the monoclinic space group P2/c as two-dimensional coordination polymers (2D-CPs). The determined structures were validated by extended X-ray absorption (EXAFS) data. Compounds 1 and 2 show different thermal stabilities. The fluorinated CP 1 is decomposed at 300 °C while the nonfluorinated CP 2 transforms into a new phase after thermal treatment at 400 °C. The two hydrated CPs exhibit small surface areas which increase after the thermal post-treatment for 1 but remains unchanged for the dehydrated sample of 2. Dynamic vapor sorption (DVS) experiments indicate that both the dehydrated and hydrated samples of 2 depict no significant differences in their adsorption isotherms. The DVS of water indicates that the phase transition after thermal post-treatment of 2 is irreversible.

Chemistry of alkaline earth metals: It is not all ionic and definitely not boring!

“…Nona-coordinated strontium ions are for instance found in metal-organic frameworks using (tetrafluoro-)phthalic acid as main ligand and water as co-ligand [97].…”

Metal-Organic Framework (MOF)—A Universal Material for Biomedicine

“…Al-Terkawi et al synthesized dicarboxylate metal-organic compounds based on alkali earth metals using the mechanochemical method. The mechanochemical synthesis was carried out by grinding the precursors Sr(OH) 2 -8H 2 O with tetrafluorophthalic acid or phthalic acid in a molar ratio of 1:1 [67]. In addition, it has been shown that the water content has a key influence on the grinding time and condition of the resulting MOFs: the lower the water content, the longer the grinding time required [68].…”

Mechanochemistry of fluoride solids: from mechanical activation to mechanically stimulated synthesis

“…Standard analytical methods like X-ray diffraction, solidstate NMR and FTIR spectroscopies, but also methods of thermal analysis, elemental analysis, BET measurements and methods of dynamic gas absorption (DVS, dynamic vapour sorption) were employed. Structure determinations were performed from X-ray diffraction powder data, since (4) the mechanochemical synthesis does not allow the formation of single crystals [86][87][88][89][90][91][92]. Figure 13 gives an insight into the structure of Ca(Sr)(p-BDC-F 4 )•4H 2 O, as one representative example of the numerous new compounds.…”