Adjusting the knife to 300 µm results in a 60-80 µm thick polymeric film after solvent removal. After casting the polymer and removing the solvent, the film appears transparent, confirming that a defect free layer was achieved The resulting film is highly homogeneous and is cut out to the desired diameter for the membrane film, as shown on photographs of the 20 wt.% MIL-116(Ga)-formate MMM in Figure . The optical micrographs shown in Figure is taken from the 10 wt.% MIL-116(Ga)-formate PSU MMM, which offered the best visibility of the homogeneous filler loadings. There are no large agglomerates or defect sites visible. When zoomed in, the membrane shows highly homogeneous filler distribution throughout the membrane. All MIL-116(Ga)-formate particles are well separated from another and no agglomerates form.