A series of four novel alkaline earth metal-organic frameworks constructed of Ca(ii), Sr(ii), Ba(ii) ions and tetrahedral MTB linker: structural diversity, stability study and low/high-pressure gas adsorption properties.

A series of four novel microporous alkaline earth metal-organic frameworks (AE-MOFs) containing methanetetrabenzoate linker (MTB) with composition {[Ca(μ-MTB)]·2DMF·4HO} (UPJS-6), {[Ca(μ-O)(μ-MTB)(HO)]·4DMF·4HO} (UPJS-7), {[Sr(μ-MTB)]·4DMF·7HO} (UPJS-8) and {[Ba(μ-MTB)(HO)]·2DMF·4HO} (UPJS-9) (UPJS = University of Pavol Jozef Safarik) have been successfully prepared and characterized. The framework stability and thermal robustness of prepared materials were investigated using thermogravimetric analysis (TGA) and high-energy powder X-ray diffraction (HE-PXRD). MOFs were tested as adsorbents for different gases at various pressures and temperatures. Nitrogen and argon adsorption showed that the activated samples have moderate BET surface areas: 103 m g (N)/126 m g (Ar) for UPJS-7'', 320 m g (N)/358 m g (Ar) for UPJS-9'' and UPJS-8'' adsorbs only a limited amount of N and Ar. It should be noted that all prepared compounds adsorb carbon dioxide with storage capacities ranging from 3.9 to 2.4 wt% at 20 °C and 1 atm, and 16.4-13.5 wt% at 30 °C and 20 bar. Methane adsorption isotherms show no adsorption at low pressures and with increasing pressure the storage capacity increases to 4.0-2.9 wt% of CH at 30 °C and 20 bar. Compounds displayed the highest hydrogen uptake of 3.7-1.8 wt% at -196 °C and 800 Torr among MTB containing MOFs.