Adsorption and Separation of Light Gases on an Amino‐Functionalized Metal–Organic Framework: An Adsorption and In Situ XRD Study

Abstract

The NH(2)-MIL-53(Al) metal-organic framework was studied for its use in the separation of CO(2) from CH(4), H(2), N(2)C(2)H(6) and C(3)H(8) mixtures. Isotherms of methane, ethane, propane, hydrogen, nitrogen, and CO(2) were measured. The atypical shape of these isotherms is attributed to the breathing properties of the material, in which a transition from a very narrow pore form to a narrow pore form and from a narrow pore form to a large pore form occurs, depending on the total pressure and the nature of the adsorbate, as demonstrated by in situ XRD patterns measured during adsorption. Apart from CO(2), all tested gases interacted weakly with the adsorbent. As a result, they are excluded from adsorption in the narrow pore form of the material at low pressure. CO(2) interacted much more strongly and was adsorbed in significant amounts at low pressure. This gives the material excellent properties to separate CO(2) from other gases. The separation of CO(2) from methane, nitrogen, hydrogen, or a combination of these gases has been demonstrated by breakthrough experiments using pellets of NH(2)-MIL-53(Al). The effect of total pressure (1-30 bar), gas composition, temperature (303-403 K) and contact time has been examined. In all cases, CO(2) was selectively adsorbed, whereas methane, nitrogen, and hydrogen nearly did not adsorb at all. Regeneration of the adsorbent by thermal treatment, inert purge gas stripping, and pressure swing has been demonstrated. The NH(2)-MIL-53(Al) pellets retained their selectivity and capacity for more than two years.

Hexane isomers sorption on a functionalized metal–organic framework

“…As the loading increases there will be less high energetic sites to occupy resulting in a lower selectivity. This effect has also been observed by Couck et al [19] in the separation of CO 2 from light gases in a functionalized NH 2 -MIL-53(Al) metal-organic framework.…”

Visualizing MOF Mixed Matrix Membranes at the Nanoscale: Towards Structure‐Performance Relationships in CO2/CH4 Separation Over NH2‐MIL‐53(Al)@PI

“…This might have implications for the gas separation performance, given that the framework fl exibility of the NH 2 -MIL-53(Al) MOF has proven to be essential for the selective separation of CO 2 . [ 18 ] Figure 4 summarizes the separation performance of MMMs containing a 25 wt% MOF loading differing in their thickness and the drying temperature applied after casting.…”

“…[ 17a ] The low pressure adsorption isotherm shows complete reversibility, i.e., the desorption branch appears superimposed on the adsorption branch, as previously reported. [ 18 ] …”

Chemistry of Metal-organic Frameworks Monitored by Advanced X-ray Diffraction and Scattering Techniques

“…106 Couck et al studied structural response to the adsorption of several light gases (CH 4 , H 2 , N 2 , C 2 H 6 , C 3 H 8 ) on NH 2 -MIL-53(Al) using in-situ XRPD and observed breathing behavior only upon CO 2 sorption process. 107 The breathing behavior was investigated by high-resolution XRD on Fe analogue of MIL-53 as well.…”