The de novo design of solid-state energy materials is challenging because function is defined by features that span multiple length scales. One example is photocatalytic solar fuels production, where the catalytic activity can depend on a range of factors such as optical gap, electronic energy levels, surface area, particle size, and hydrophilicity. Organic materials are promising candidates for photocatalytic hydrogen production, but predicting the best combination of properties is difficult because the underlying structure-activity rules are poorly understood. So far, most studies involving heterogeneous organic photocatalysts have been conducted on carbon nitride materials or amorphous conjugated polymers, where insolubility and lack of long-range order make thorough structural characterization difficult. Consequently, it is hard to deconvolute the structure-activity relationships in organic photocatalysts where the extended packing is poorly defined.