We used the BRICS algorithm on the GA-generated polymers to understand which chemical building blocks are frequently observed in the top performing polymers. The top six frequently observed functional groups with the 100 fittest GA-generated polymers are shown in Figure . We identified a total of 464 chemical fragments within the fittest 100 polymers, and 18% of the fragments were pyridine functional groups. More than 70 polymers in the top performing GA-generated polymers have the pyridine functional group in their repeating unit. This is by far the most frequently observed functional group, which is then followed by benzoxazole with 3%. We observe benzoxazole functional group in 13 polymers within the 100 fittest GA-generated polymers. Similarly, benzene, phosphonamidic acid, naphthalene, and dibromobenzene functional groups are also observed in the top performing polymers generated with the GA. We show six example polymer structures that have high fitness function values in Fig- . We note that these polymers have pyridine, benzoxazole, benzene, and phosphonamidic acid functional groups, which we identified as the most abundant functional groups with the BRICS algorithm. These polymers also include oxygen-, sulfur-, and nitrogen-containing motifs, similar to the three experimental polymers that are above the CO 2 /N 2 upper bound.