The influence of the preheated PSf substrate on COF-LZU1 layer formation and the performance for salt and pharmaceutical rejection

Construction of covalent organic frameworks (COF) membranes on the polymeric substrate was challenging by interfacial polymerization (IP) process. In this study, COF-LZU1 membranes were fabricated by IP on the preheated PSf substrates to investigate the influence of substrate properties (i.e., pore size and porosity) on the COF-LZU1 layer formation. The substrates with tunable pore size (18.61 to 14.53 nm) and porosity (2.05 % to 0.42 %) could be obtained with the pretreating temperature of 20 °C to 50 °C. Preheated substrate altered monomer storage and diffusion, leading to the variations in crosslinking degree (14.89 % to 87.63 %) and observed thickness (142.9–575.9 nm). The preheated substrates endowed better growth conditions by inhibiting the COF-LZU1 intrusion into the substrates, and optimal COF 40°C membrane had water flux of 6.57 L m −2  h −1 , and Na 2 SO 4 rejection ratio of 90.9 %. The rejection ratio of pharmaceuticals by COF-LZU1 membranes was low due to adsorption. Correlation analysis showed that the C N bond content was unfavorable for absorption ( P  < 0.05), and the increase of crosslinking and crystallinity of the COF-LZU1 layer will be beneficial to boost the pharmaceutical rejection. This work provided a facile method and valuable insight for the COF-LZU1 membrane fabrication to enhance desalination and pharmaceutical removal.