The　growing　complexity　of　dyeing　and　printing　effluents　has　presented　considerable　challenges　for　their　effective　treatment　and　recycling.　Recently,　there　has　been　a　notable　increase　in　the　development　of　loose　nanofiltration　(NF)　membranes,　which　are　characterised　by　their　exceptional　environmental　resilience,　high　throughput,　and　superior　dye/salt　selectivity.　This　work　presents　the　development　of　a　new　loose　NF　membrane　prepared　from　a　modified　polymer　called　poly(ether　sulfone　ether　ketone　ketone)　(PESEKK).　The　membrane　features　a　dense-loose-support　structure　and　is　prepared　through　a　straightforward　one-step,　non-solvent　induced　phase　separation　(NIPS)　technique,　eliminating　the　need　for　heating　or　post-treatment.　Precise　regulation　of　membrane　pore　size　down　to　4.27　nm　can　be　achieved　through　modulation　of　PESEKK　and　pore-former　composition.　The　membranes　could　separate　positively　and　negatively　charged　dyes　in　mixed　dye　solutions　accurately　and　selectively.　Additionally,　the　membrane　demonstrated　exceptional　dye/salt　selective　separation　with　a　high　water　flux　of　230.7　L　m−2　h−1　bar−1,　Congo　red　rejection　of　99.91　±　0.13　%,　NaCl　rejection　of　2.71　±　0.23　%,　and　a　separation　factor　(α)　of　347.4,　outperforming　state-of-the-art　membranes.　Remarkably,　PESEKK　membrane　maintained　outstanding　stability　and　separation　performance　for　up　to　200　h　under　extreme　environments,　including　NaOH　solution　(up　to　9　mol　L−1),　NaClO　solution　(up　to　40,000　mg　L−1　h),　n-hexane,　isopropanol,　and　methanol.　This　high-performing　loose　NF　membrane,　developed　using　innovative　polymer　materials,　offers　a　promising　solution　for　treating　the　challenging　wastewater　generated　by　printing　and　dyeing　processes.　©　2025　Elsevier　B.V.