At first glance, these results could suggest that porosity is the dominant factor for hydrogen evolution, because the porous TBAP-α structure greatly outperforms the non-porous analogues, even though TPyP-α also contains significantly overlapped π-stacking. This may however be an oversimplification. As evident from water sorption isotherms, TBAP-α has no significant water uptake between partial pressures of 0.2-0.6 (Figure ). There is significant water uptake at higher relative pressure, which might suggest water adsorption but could also indicate water molecules condensing on the crystal surfaces or between crystals. We note that this wetting behaviour may be different in the presence of the sacrificial agent, ascorbic acid, and in this respect, water sorption isotherms may not reflect the photocatalysis conditions.