Publication: Computational insights into efficient CO2 and H2S capture through zirconium MOFs
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Abstract
Separation of CO2 involving mixtures is relevant to the various industrial settings and preserving environment for which different classes of materials including metal-organic frameworks (MOFs) have been researched. Herein, CO2/CO, CO2/H-2, CO2/N-2, and H2S/CO2 separation properties of the zirconium MOFs are computationally investigated mimicking vacuum swing adsorption (VSA) process. Structure-performance relationships are established and the best performing adsorbent materials are determined considering three performance metrics: adsorption selectivity, working capacity, and regenerability. For CO2/CO separation in dry conditions, PCN-59, BUT-10, and PCN-58 are identified to be the top three materials with CO2/CO selectivities of 219.8, 47.2, and 28.6, CO2 working capacities of 6.9, 5.3, and 4.0 mol/kg, CO2 regenerabilities of 63.3, 82.1, and 87.2 %, successively. In humid conditions, UiO-66-OH and MOF-805 appear promising for CO2/CO separation. Regarding CO2/H-2 separation in dry conditions, PCN-59, BUT-10, and LIFM-94 are ranked as the top three MOFs exhibiting CO2/H-2 selectivities of 1445.6, 378.1, and 411.3, CO2 working capacities of 3.6, 2.4, and 2.2 mol/kg, and CO2 regenerabilities of 56.6, 84.9, and 83.9 %, successively. These three materials are also found to be the top three materials for CO2/N-2 separation in dry conditions with CO2/N-2 selectivities of 346.0, 53.3, and 54.9, CO2 working capacities of 3.6, 2.3, and 2.2 mol/kg, and CO2 regenerabilities of 56.3, 84.1, and 83.9 %, successively. For CO2/H-2 and CO2/N-2 separation in humid conditions, UiO-66-NH2 is potentially useful. Considering H2S/CO2 separation in dry conditions, NU-1101, PCN-58, and LMOF-1 are identified to be the best three MOFs attaining H2S/CO2 selectivities of 109.7, 30.9, and 90.7, H2S working capacities of 1.6, 2.3, and 1.2 mol/kg, and H2S regenerabilities of 43.0, 56.4, and 43.7 %, respectively. All top materials for H2S/CO2 separation show relatively large water affinities (PCN-57 having the smallest affinity) which might render them inefficient for H2S/CO2 separation in humid conditions. Adsorbate density profiles are generated for the top 3 materials to elucidate the adsorption mechanisms for each gas separation. A comparison of predictions based on PACMOF and EQeq charges demonstrates drastic differences in material rankings, and separation performance metrics.
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Source:
Journal of CO2 Utilization
Publisher:
Elsevier
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Chemistry, Engineering