The modification of poly(oxindole biphenylylene) (POXI) membranes by photoinduced thiol-yne click approach is presented. Initially, a propargyl-functionalized porous poly(oxindole biphenylylene) (POXI-PG) membrane was prepared by condensation reaction of isatin and aromatic hydrocarbons with a superacid-catalyst. Subsequently, the solution and surface functionalization of POXI-PG by one-step photoinitiated thiol-yne click reaction with various thiol functional molecules, namely pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), 1,2-ethanedithiol (EDT) and thiol modified poly(ethylene glycol) methyl ether (PEG-SH) was demonstrated. The spectral and thermal investigations via FT-IR, 1H NMR, XPS and DSC analyses confirmed the success of the modification process. The POXI-PG membranes crosslinked with PETMP had the molecular weight cut off (MWCO) reduced from 75 to 5 kg mol−1. They became stable in different organic solvents with permeations between 0.4 and 2.8 L m−2 h−1 bar−1.