The layered MOF Cu 3 (HHTP) 2 (Fig. ) was chosen as the model electrode material for this study as it has a well-defined pore size and structure, and its electrochemical performance has been characterised in detail in previous work. Polycrystalline samples of Cu 3 (HHTP) 2 were synthesised using a previously reported literature synthesis (see Supplementary Information), and the chemical composition of the framework was confirmed by elemental analysis, which revealed the expected ratio of Cu and HHTP (SI Table ). Elemental analysis also showed that some nitrogen-containing impurities remain in the framework after extensive washing and activation, consistent with previous reports. Scanning electron microscopy (SEM) confirmed that the use of ammonia as a modulator in the synthesis resulted in the formation of flake-like crystallites, which were previously shown to be the crystal morphology that exhibits the best performance in Cu 3 (HHTP) 2 supercapacitor devices (SI Fig. ). PXRD patterns confirmed the high crystallinity of as-synthesised Cu 3 (HHTP) 2 (SI Fig. ) and indicated that this material has a hexagonal eclipsed unit cell with AA layer stacking. Unit cell parameters of a ≈ b = 21.2 Å, and an interlayer spacing c = 3.1 Å were calculated from the PXRD patterns. This leads to a predicted crystallographic pore size of 16 Å. The pore size distribution of this material, along with its porosity, were further analysed using 77 K N 2 sorption isotherms (SI Fig. ). Brunauer-Emmett-Teller (BET) analysis on two independent samples confirmed that the material synthesised in this work is highly porous, with a BET surface area of 802 ± 40 m 2 g -1 obtained. Importantly, pore size distribution (PSD) analysis confirmed that Cu 3 (HHTP) 2 has an ordered, unimodal pore size distribution centred at 15.0 Å (Fig. ), in good agreement with the crystallographic pore size. This further confirms the well-defined long-range order of this material. This is in contrast to porous carbons, which have significantly more disordered structures with little long-range ordering and broad pore size distributions (SI Fig. ). Overall, this supports the use of layered MOFs, such as Cu 3 (HHTP) 2 , to establish structure-performance relationships in supercapacitors.