Figure 5: Crystallographic resolution of CO₂ and C₂H₂ binding in MFM-188a.

Framework atoms: C, black; O, red; H, white; N, blue; Cu, blue. Extra framework gas molecules are slightly magnified and coloured according with the binding site they occupy. Distances are shown in Å. View of the binding of adsorbed CO₂ molecules at site 1 (a), 2 (b) and 4 (c). (d) View of the packing of adsorbed CO₂ molecules within cage C. View of the cooperative binding of adsorbed C₂H₂ molecules at site 1, 2, 4 (e) and at site 3 (f).