Quantifying the strain of the CS framework gives insight into the breathing behaviour of the interpenetrated structure and how it is affected upon uptake and exchange of guest molecules. All guest and solvent molecules were removed from the DFT optimised CS structures before running single-point energy and geometry optimisation calculations to find the intramolecular strain energy of the framework, ∆E MOF , as described in Section 2.3. Calculated ∆E MOF values are reported per minimum framework unit ((ZnX 2 ) 3 (tpt) 2 , 81 atoms) and can be found in Table . Structure information and cell volume changes are found in Table .