PDMS/PAI-HF composite membrane containing immobilized palladium nanoparticles for 4-nitrophenol reduction

Abstract Catalytically active asymmetric membranes were developed by crosslinking a polydimethylsiloxane (PDMS) thin layer onto a porous polyamide‐imide hollow fiber (PAIHF) support, followed by grafting of aminosilane with hydroxyl derived-PDMS/PAIHF, and finally palladium nanoparticles (PdNPs) immobilization using salicylic aldehyde. Aminosilane and salicylic aldehyde linkers were used to permanently immobilize PdNPs onto the PDMS surface through metal coordination chelation, which prevented their agglomeration and leaching from the catalytic membrane reactor (CMR) module. The obtained CMRs were used for hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in a continuous-flow fashion. The effects of 4-NP concentration (0.5–4 mM) and flow rate (0.01–0.08 cm3 min−1) on 4-NP conversion and 4-AP selectivity were evaluated in both batch and continuous-flow systems. The newly developed continuous flow 4-NP hydrogenation module exhibited a good operating stability after six cycle run for 6 h’ time on stream, where complete 4-NP conversion (100%) was achieved in short residence time (2–3 s) via a single-pass-through the CMR module. Overall, the designed and developed method described herein offers an alternative platform to address PdNPs’ leaching issues that are commonly encountered in continuous-flow chemical transformation processes.