Insight into the effect of changing the halide ion within the framework can be gained from comparison of ZnCl 2 and ZnBr 2 analogues containing the same guest molecule. The experimental structures VUKYUX (ZnCl 2 ) and VUKYOR (ZnBr 2 ) containing 1R-(-)-menthyl acetate are included in this study. The 1R-(-)-menthyl acetate guest molecules are present in the same exchange sites in both structures, with additional presence of one and two CHCl 3 solvent molecules, respectively. Calculated framework strain values show a large difference between each system: ∆E av MOF =3.41 kJ/mol for ZnBr 2 , with an overall cell volume increase of 0.05%, and ∆E av MOF =20.7 kJ/mol for ZnCl 2 , with an overall cell volume reduction of 6.27%. The ZnCl 2 structure also has an overall smaller experimental unit cell size than the ZnBr 2 structure (15,720.4 Å 3 versus 16,176.6 Å 3 ). It is clear that guest exchange causes greater distortion of the ZnCl 2 framework due to smaller overall pore volumes, resulting in higher framework strain.