We first optimized the structures with the Merck Molecular Force Field method (MMFF94), implemented using OpenBabel. To refine the geometries, we subsequently optimized the geometries using DFT. We ran single point DFT calculations on both the force fieldoptimized and DFT-optimized geometries to determine the quantum chemical characteristics used in our analysis. For all catalysts, these single-point energies were computed for both the neutral and cationic forms. All DFT calculations were performed in Q-Chem 34 using the PBE0 functional and 6-31g* basis set. Starting from the DFT-optimized geometries, we ran O2-binding DFT calculations to enumerate all possible O2-binding locations and energies. As the known active sites for nitrogen-doped carbon catalysts are all carbon atoms, we prepared each input geometry by placing one O2 per calculation at a distance of 1.55 Å oriented with a C-O-O bond angle of 120° from each carbon in the dataset of 258 molecules. This totaled to 4039 O2 binding calculations. We then calculated the optimized geometries for each of these systems using DFT and generated electronic features as before. These calculations provided the output sets for our supervised learning tasks: the binary binding/non-binding determination for the classification task, and the O2-binding energy for the regression task. We calculated the O2 binding energy using the formula, 𝐸 ! ! #$%&$%' = 𝐸 ()*! ! -𝐸 ()* -𝐸 ! ! , momentarily neglecting entropy and solvent corrections. We then used the values of 𝐸 ! ! #$%&$%' and the optimized geometry of each calculation to label whether the site binds O2; a full description of this labeling process is in section 1 of the SI, but in the majority of cases we labeled a site as active if the C-O bond length was less than 2 Å and the binding energy was less than -0.1 eV. We chose to use a threshold of -0.1 eV because there were a number of cases where O2 did not form a bond, ending the optimization at over 3 Å from the catalyst, but 𝐸 ! ! #$%&$%' was between 0 and -0.1 eV due to fractional electron transfer to O2. Furthermore, given that the success of the O2-binding reaction at such weakly-binding sites can be sensitive to the initial geometry used, we determined that the most consistent way to label these sites was as non-binding for O2 (see SI section 1).