Fabrication of triptycene-based polyamide low-pressure reverse osmosis membranes for high-efficiency desalination

Low-pressure reverse osmosis (RO) is a key technology for energy-efficient desalination, but traditional RO membranes suffer from the bottlenecks of permeability-selectivity trade-off and the requirement for high-pressure operation. To address this issue, this study synthesized a novel triptycene-based acyl chloride monomer (PETC) and prepared a polyamide thin-film composite membrane via interfacial polymerization with polyethyleneimine (PEI). The rigid non-planar framework of triptycene increases the free volume of the polyamide network, and its high-density benzene rings construct hydrophobic microdomains, which synergistically promote water molecule transport while inhibiting hydrated ion permeation. The optimized PETC-PEI membrane exhibits excellent low-pressure desalination performance: the NaCl rejection rate reaches 96.7% and the pure water permeability is 4.7 LMH/bar, which is significantly superior to the control TMC-PEI membrane (rejection rate: 50.9%; permeability: 2.48 LMH/bar), and it also has good long-term stability. This study provides a new molecular design strategy for high-performance low-pressure RO membranes and opens up a new path for the next generation of low-energy desalination technologies.