Enhanced gas-sorption properties of a high surface area, ultramicroporous magnesium formate

The direct solvothermal reaction of Mg(NO 3 ) 2 ·6H 2 O in dimethylformamide at 130 °C leads to the formation of highly crystalline α-[Mg 3 (O 2 CH) 6 ] with an expanded unit cell. Successful pore activation was performed after heating the material at 240 °C under dynamic vacuum. In contrast to literature reports, the pores in the activated solid are accessible to nitrogen molecules and the corresponding BET surface area is 496 m 2 g −1 , very close to the geometric area calculated from the single crystal structure. A detailed gas-sorption study (N 2 , Ar, H 2 , CO 2 , CH 4 and NH 3 ) is reported. The material is ammonia stable showing a reversible uptake of 5.4 mmol g −1 at 298 K, while the corresponding CO 2 uptake is 2.2 mmol g −1 with moderate CO 2 /CH 4 (4.6) selectivity but high CO 2 /N 2 (23) and CH 4 /N 2 (5.2) selectivity. The latter is among the highest values reported to date in the entire family of porous materials. The H 2 uptake at 77 K is 1.2 wt% which is the highest among the reported values for various magnesium formates.