This work represents a pioneering effort in utilizing continuous flow methods for the post-synthetic modification of a nanoporous metal-organic framework (Fe-BTC or MIL-100(Fe)) with short-chain redox-active oligomers (poly-p-phenylenediamine, PpPDA). The Fe-BTC/PpPDA composite has been previously demonstrated to rapidly and selectively extract gold from complex liquids. Thus, in the present study, Fe-BTC/PpPDA was synthesized on a 250 g scale and tested in eight industrially relevant solutions used for leaching metals from electronic waste. These leachates (e. g., cyanide, thiourea, and aqua regia) exhibited varying effectiveness, pH, and gold speciation, which led to significant differences in the composite's performance during gold extraction. Notably, Fe-BTC/PpPDA performed best in leaching solutions containing [AuCl