Fig. 1: The evolution of N/O doping from simplicity to complexity.

a Aqueous solubility of simply common aromatic hydrocarbons and their corresponding N/O doping analogs at 25 °C (data in parentheses was obtained from hazardous substances data bank). b Molecular structure design via diversified aromatic polycycles fusion. c Combination of programmed N/O doping towards pristine C1 structure (highlighted molecules demonstrate excellent aqueous solubility).