Mg²⁺ embedded MIL-101(Cr)-NH₂ framework for improved CO₂ adsorption and CO₂/N₂ selectivity

Abstract

The development of a CO₂-selective adsorbent with high CO₂, uptake capacity and CO₂/N₂: selectivity is a challenge. In this work, Mg²⁺-embedded MIL-101(Cr)-NH₂, frameworks (Mg@MCrN) were simply prepared via a facile one step synthesis. The results indicated that the incorporation of a proper amount of Mg²⁺ into the host MIL- 101(Cr)-NH₂, increased the porosity of the resultant adsorbent. Noticeably, the temperature-programmed desorption of CO₂ (TPD-CO₂) analysis revealed that the prepared Mg@MCrN contained new metal active sites along with coordinately unsaturated Cr(III) sites and amine (NH₂) sites of the framework. At 100 kPa and 25°C, the prepared Mg@MCrN-0.2 exhibited the highest CO₂, uptake capacity and CO₂/N₂ selectivity of ca ~3.04 mmol.g¹ and ca.~ 60, respectively, surpassing the parent MOF and many other CO₂ benchmark adsorbents. Moreover, the CO₂ adsorption capacity over the Mg²⁺-incorporated MIL-101(Cr)-NH₂ remained even after 5 cycles of adsorption-desorption under pressure swing from 0 to 100 kPa. This work opens a new perspective for developing efficient CO₂ selective materials.