To initialize the fragment library, we break down the promising candidate molecules from For each candidate molecule i (i ∈ N F in , step 1 ○), we begin by analyzing the molecular 215 structure and identifying its functional groups (step 2 ○). To tailor the functional groups, we draw inspiration from the drug development and discovery field, where fragment-based molecular design is extensively employed. To this end, many computational tools for building the fragment libraries or fragmenting the molecules are being developed. Two widely utilized methods for fragmenting are Retrosynthetic Combinatorial Analysis Procedure (RECAP) and Breaking Retrosynthetically Interesting Chemical Substructures (BRICS). Based on the chemical substructures used in RECAP and BRICS, we predefine 16 functional groups for our Fragmentation phase, as listed in Table .