Water effect on adsorption carbon capture in metal-organic framework: A molecular simulation

Considering water vapor is a component in almost all CO 2 -rich industrial gas streams, it is of critical importance to understand interaction mechanisms between adsorbent and adsorbate. This paper aims to comprehensively analyze water effect on CO 2 adsorption for metal-organic framework (MOF) in a broad working pressure range which may bring some new insights based on a molecular simulation. First, Mg-MOF-74 is selected and synthesized according to previous literature. Equilibrium adsorption capacity and enthalpy are obtained by grand canonical Monte Carlo simulation, and the results for high-pressure CO 2 adsorption are validated through magnetic suspension balance experiment. It is indicated that there are three adsorption stages for pure CO 2 and four adsorption stages for pure H 2 O under different pressure. Adsorption enthalpy also varies with adsorption capacity, which is fully explained from the angle of adsorption stages and energies. Further simulation of flue gas (CO 2 /H 2 O/N 2 ) adsorption at different humidity are carried out, and selectivity between CO 2 and H 2 O is analyzed. At 298 K, 100 kPa, with 3% water content, CO 2 /H 2 O selectivity is 5.6 × 10 −5. When temperature rises to 388 K, CO 2 /H 2 O selectivity rises to 6.2 × 10 −3. Adsorption density distributions, simulation snapshots, and radial distribution functions are used in analysis processes, which could provide a general perspective for analyzing CO 2 adsorbents in the presence of H 2 O.