Modification of a cobalt–aluminophosphate (Co/Al ∼ 1) with a multidimensional pore system via coupled partial detemplation and solid state ion exchange with alkali metals for the adsorption of light gases

SBE type metal substituted aluminophosphates (MeAPOs) are materials with multidimensional pore frameworks that are highly unstable to oxidative and high temperature conditions due to the large content of transition metal centers. Nevertheless, in this study we have shown that it is possible to effectively functionalize these materials using coupled vacuum assisted partial detemplation and solid-state ion exchange (PD/SSIE) at mild temperatures. A cobalt-rich SBE type aluminophosphate (CoAPO (SBE); Co/Al ∼ 1) was detemplated and SSIE with either Na+ or Li+ in an attempt to modify its surface while preserving the framework and textural characteristics. The resulting porous materials were also tested for the equilibrium adsorption of CO2 to elucidate the level of adsorbate–adsorbent interactions and, therefore, the potential for gas separation processes via adsorption. The best ambient temperature CO2 loading capacities were observed in the sodium-SBE variants at both low and high partial pressure ranges. Furthermore, this adsorbent material exhibited good selectivity toward CO2 over CH4 or N2, particularly at low partial pressure and likely due to the interaction of accessible sodium extraframework cations with the strong quadrupole moment of the CO2 molecules. Although the adsorbent materials discussed here have yet to display capacities that match those of some commercial porous materials, the findings could serve as a platform for the development of MeAPOs with multidimensional pore systems and superior surface characteristics.

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► Produced first CoAPO (SBE) adsorbent materials containing extraframework cations.
► Framework and textural properties were preserved despite SBE framework low stability.
► Sodium based materials exhibited better CO2 adsorption loadings and selectivity.