The workflow for our ML method to learn synthesis-property relationships of gas separation membranes is shown in Fig. . In Step 1, the training set consists of the single repeating units of 353 unique homopolymers with at least one known gas permeability (among He, H2, O2, N2, CO2, and CH4), as obtained from the PoLyInfo and Membrane Society of Australasia 53 (MSA)