Amine-functionalized MIL-53(Al) for CO2/N2 separation: Effect of textural properties

A high-quality amine-functionalized metal organic framework, amino-MIL-53(Al), was synthesized by a solvothermal method in DMF and evaluated as an adsorbent for CO2/N-2 separation both at ambient and high-pressure conditions. The textural properties of the amino-MIL-53(Al) gradually improved as the synthesis time was extended, and the optimized sample showed excellent crystallinity accompanied by a high surface area (937 m(2) g (1)) and large pore volume (0.53 cm(3) g (1)), both of which being significant improvements over the literature values reported by Kapteijn et al. (675 m(2) g (1) and 0.22 cm3 g (1)). The amino-MIL-53(Al) framework exhibited the typical breathing behavior of both CO2 and N-2 during high-pressure gas adsorption measurements. This characteristic was affected not only by the adsorption temperatures but also by the textural properties of the adsorbents. The amino-MIL-53(Al) framework achieved both high CO2 sorption capacities (82 and 302 mg g (1) at 0.1 and 3.0 MPa, respectively) and high selectivity against N-2 (> 30 at 2.0 MPa) at 298 K due to the open-metal sites and free-standing amino groups. The heat of adsorption for CO2 near zero coverage by amino-MIL 53(Al) was ca. 60 kJ mol (1) compared to ca. 50 kJ mol (1) by MIL-53 (Al), providing evidence of the contribution of the amino groups towards CO2 adsorption. Repeated pressure swing adsorption-desorption cycles six times between 0.5 and 2.0 MPa both at 298 and 323 K showed no deterioration in the CO2 adsorption capacity. Reversible adsorbent regeneration was also maintained for a total duration of 240 min. (C) 2012 Elsevier Ltd. All rights reserved.