Since the mussel-inspired multifunctional coating was introduced in 2007, it has been utilized to modify membranes for a wide range of applications including ultrafiltration and nanofiltration. In this work, the effects of substrate pore size and coating conditions on the separation performance of organic solvent nanofiltration (OSN) membranes were investigated. By using sulfonated polyphenylenesulfone (sPPSU) as the substrate material and polyethyleneimine and pyrocatechol as the coating materials, OSN membranes can be fabricated if the pores of the sPPSU substrates are less than 12 nm in diameter (determined by the solute transport method). The coated membranes show rejections greater than 93% towards molecules with molecular weights larger than 645 g/mol and a permeance of 11.9 L m(-2)h(-1)bar(-1) in ethanol. The addition of epichlorohydrin in the coating solution can significantly enhance membrane rejections to small molecules. The fabricated membranes demonstrate good stability in 7-day tetracycline filtration tests. The 2-pass rejection can reach 96.2% to tetracycline for tetracycline/isopropanol solutions. The newly developed one-step facile coating method has great potential to fabricate membranes for OSN applications in the pharmaceutical industry. (C) 2019 Elsevier Ltd. All rights reserved.