To test this, we deliberately produced amorphous material by the rapid precipitation of TBAP from a basic solution (SI, general methods and Figure ). We found that this amorphous TBAP had a very poor photocatalytic activity (Table , Figure ); with 1 wt. % photodeposited Pt, the rate was 6 µmol g -1 h -1 (after an induction period). This rate is over 200 times lower than the rates observed for crystalline TBAP-α under equivalent conditions. This rationalizes the steady loss of activity that is observed for TBAP-α as the crystallinity is reduced during photocatalysis.