Concentration-Dependent Binding of CO2 and CD4 in UiO-66(Zr)

Porous metal–organic frameworks (MOFs) have emerged as promising materials for the capture of carbon dioxide (CO 2 ) and its separation from methane (CH 4 ) during the industrially important “sweetening” of sour natural-gas. The excellent thermal and chemical stability of the highly porous UiO-66(Zr) material, combined with good selectivity for CO 2 over CH 4, makes this material a prime candidate for such applications. Using a combination of neutron powder-diffraction and density-functional theory, we examine the details of the binding of CO 2 and CH 4 in UiO-66(Zr) over the industrially relevant 3.6–9.0 mmol/g concentration range, corresponding to the material that is half to fully saturated with CO 2 . This work builds on the previously reported preferred site for CO 2 and CH 4 in UiO-66(Zr), establishing further sites and determining the strength and nature of the guest–host interaction at these. We find the UiO-66(Zr)···CO 2 interactions are significantly affected by the concentration of CO 2 as the binding of CO 2 is enhanced by interguest interactions.