The presence of dye wastewater in the environment has raised serious concerns. In this regard, thin-film composite (TFC) membranes featuring porous organic polymers (POPs) as the selective layer have attracted considerable attention, owing to the high specific surface area and excellent chemical stability of POPs. This research was organized around designing the selective layer structure of a polyacrylonitrile (PAN)/POP TFC membrane to suit dye wastewater purification. The monomers triaminoguanidinium chloride (TGCl) and terephthalaldehyde (TPA) were utilized in interfacial polymerization on a microporous hydrolyzed PAN (HPAN) support to fabricate a POP thin film. The molecular dimensions of Acid Red 114, Acid Blue 62, and Basic Brown 1 were calculated using molecular dynamics (MD) simulations. By changing the organic solvent from benzene to toluene and adjusting the POP synthesis temperature, the water permeability of the TFC membrane decreased from 21.29 L·m−2·h−1·bar−1 to 5.98 L·m−2·h−1·bar−1. High dye rejection of 98.3 % for Acid Red 114 and 97.6 % for Basic Brown 1 were recorded for the developed TFC membrane. Long-term stability was maintained over 24 h during the purification of 100 ppm dye wastewater. The enhanced structural stability of the POP layer in the TFC membrane with superior performance was confirmed by the DMF-immersion protocol, which demonstrated a higher degree of polymerization and the formation of a more compact network. This study also emphasizes the trade-off between the POP layer structural stability and the TFC membrane permeability, where enhancing the integrity of the POP layer was prioritized over maintaining high flux to ensure long- term performance.