Freestanding composite electrode films were prepared by adapting an existing literature method. f-CMK-3 powder (50 mg) was mixed with ethanol (ca. 1.5 mL) to produce a loose slurry. This was sonicated for 15 min before being added to a PTFE dispersion in a few drops of ethanol in a watch glass. The slurry was stirred by hand in the watch glass for 30 min under ambient conditions. The film was gradually formed upon ffdrying of the slurry before being transferred to a glass surface, where it was kneaded with a spatula for 10 mins to ensure homogenous incorporation of the activated material and PTFE and then rolled into a freestanding film using a homemade aluminium rolling pin. The film was dried in vacuo at 100 °C for at least 24 h to remove any excess ethanol. The masses of components were calculated so that the final film had a composition of 95 wt% f-CMK-3 and 5 wt% PTFE.