Metal organic polyhedra (MOP) are single, tunable molecular cages that can be used for CO2 sorption at high pressure and high temperature.  The thermally and chemically stable MOP-18 was synthesized and tested for gas sorption as a crystal and dispersed in a polymer matrix at pressures up to 60 bars at 35 �C and at 70 �C.  Gas sorption isotherms for CO2, H2, N2, and CH4 were acquired for the MOP-18 crystals, a Matrimid� membrane, and a 23 wt% MOP-18/Matrimid� mixed-matrix membrane (MMM).  The MOP-18 crystals showed CO2 adsorption of 2 mmol/g at 35 �C and 50 bar and 1 mmol/g at 70 �C and 50 bar, but no significant adsorption for H2, N2, and CH4.  The low gas adsorption in MOP-18 crystals was attributed to the blockage of the MOP pores by the alkyl chains of the linker.  In contrast, in the MMM, the alkyl chains of the linker extend from the core exposing the pore aperture of the molecular cage, thus allowing for significant CO2 sorption starting at 30 bar at either 35 �C or at 70 �C.  The amount of CO2 adsorbed by the MOP-18 in the membrane at 50 bar was found to be 22 mmol/g, higher than the amount adsorbed by activated carbon (6-8 mmol/g) and tetraethylenepentamine (21 mmol/g).  The isotherms also showed that at 50 bar the MMM was still adsorbing CO2 and did not reach a plateau, suggesting that the CO2 adsorption capacity of MOP-18 may be even higher than 22 mmol/g.

Carbon dioxide sorption in metal organic polyhedras at high pressure and high temperature

248th National Meeting (2014)

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