TPhP-α, TPyP-α, TBAP-α had light absorption onsets well into the visible region (Figure ). We therefore tested activity for sacrificial photocatalytic hydrogen production under visible light (λ > 420 nm, 300 W Xe light source) with 1 % wt. platinum co-catalyst, using ascorbic acid as the sacrificial hole-scavenger. TBAP-α was by far the most active material under these conditions with an initial hydrogen evolution rate (HER) of 1293 µmol g -1 h -1 (Table , Figure ). This is the first example of a crystalline porous HOF that shows appreciable photocatalytic hydrogen evolution from water under sacrificial conditions, challenging the paradigm that covalent networks such as COFs or extended polymer chains are required. These photocatalytic rates are significantly higher than for amorphous pyrene-based CMPs (HER λ > 420 nm = 174 µmol g -1 h -1 using diethylamine as the hole-scavenger). The external quantum efficiency (EQE) of TBAP-α was estimated to be 4.1% at 420 nm using monochromatic light from a LED source, which is higher than many conjugated polymer catalysts such as a benzodithiophene-bipyridine CMP, PCP4e (EQE350 nm = 0.34%) and a tricyano-benzenecentered phenylenevinylene-co-terphenylene polymer network, OB-POP-3, (EQE420 nm = 2.0%), but lower than dibenzo[b,d]thiophene-CMP S-CMP3 (EQE420 nm = 13.2%), and certain linear conjugated polymers, such as poly(dibenzo[b,d]thiophene) P10 (EQE420 nm = 11.6%). At 470 nm, the EQE for TBAP-α is reduced to 1.2% and no significant activity is observed at 595 nm. As such, the photocatalytic efficiency follows the absorption profile of TBAP-α (SI, Figure ). No hydrogen production is observed in the dark or in the absence of the TBAP-α. When D2O was used as the proton source, D2 production was mostly observed (SI, Figure ), with a small amount of H2, probably due to H-D exchange with protons in the non-deuterated ascorbic acid. Essentially no CO production is observed under these conditions (SI, Figure ). Taken together, these observations lead us to conclude that the hydrogen production process is indeed photocatalytic.