PXRD and N 2 sorption analysis confirmed that the long-range order and porosity of Cu 3 (HHTP) 2 is largely maintained upon forming a composite electrode film with PTFE and a conductive additive for use in electrochemistry experiments (SI Fig. ). However, the N 2 sorption analysis reveals a decrease in the porosity of Cu 3 (HHTP) 2 in the electrode films, with a BET area of 545 ± 7 m 2 g -1 calculated for the constituent Cu 3 (HHTP) 2 after removing the contribution of acetylene black and assuming PTFE does not contribute to the adsorption. This represents a decrease in the surface area of Cu 3 (HHTP) 2 of approximately 32% compared to powder samples. Furthermore, there is a slight reduction in the modal pore size to 14 -14.2 Å. This shows that PTFE and/or acetylene black are blocking some of the pores and reducing the available surface area of the MOF. While infiltration of polymers into the pores of MOFs has been observed previously using NMR, this effect had not previously been quantified for conductive layered MOFs. While a decrease in porosity has also been observed for porous carbon materials when made into composite electrode films, the percentage decrease in surface area was much smaller. This was confirmed in this work, where a decrease of 4% in the BET area of YP80F was observed upon formation of an electrode film (SI Fig. ). This suggests that the binder and conductive additive are significantly more effective at blocking the ordered one-dimensional porosity in layered MOFs. Optimisation of layered MOF composite electrode films, by changing both the conductive additive and binder, may help to minimise this effect and improve the performances of these materials in supercapacitors. Having confirmed the well-defined structure of Cu 3 (HHTP) 2 , we proceeded to use this layered MOF to probe the cation size-performance relationship. OCV (positive charging; red), -0.5 V vs. OCV (negative charging; blue), and across the full potential window (black). Cu3(HHTP)2 was stable and showed minimal Faradaic peaks between the chosen potential limits for each electrolyte, confirming mainly double-layer charge storage for each electrolyte in this potential range. The direction of scanning is indicated by the arrow in each case. (e) Specific capacity values calculated from galvanostatic charge-discharge (GCD) profiles at a current density of 0.05 A g -1 when charging to +0.5 V vs. OCV(red) and -0.5 V vs. OCV (blue). The red and blue dashed lines are added as guidelines. The mass of Cu3(HHTP)2 in the working electrode was used to calculate specific capacity values. This shows how the charge storage changes with cation size for both positive and negative charging.