To investigate further, we conducted photocatalysis experiments using large (13 nm by DLS, SI Figure ) pre-made platinum nanoparticles as the co-catalyst source, rather than photodeposition of Pt from solution. These pre-made Pt particles are too large to fit within the 1.9 × 2.1 nm TBAP-α nanopores and, hence, if these pores are the main sites for hydrogen evolution, then we might expect to see a very large decrease in rate compared to materials with photodeposited Pt particles, which might be small enough to form within the pore channels. This was not observed. The rate with the pre-formed nanoparticles was 813 µmol g -1 h -1 ; that is, only around 30% lower than for the photodeposited Pt sample under those catalysis conditions (1293 µmol g -1 h -1 ). ICP-MS analysis indicated the Pt contents were similar for both the photodeposited and the pre-made Pt materials and STEM imaging showed deposition had occurred in both cases.