Covalent organic frameworks (COFs) with β-ketoenamine structure have shown notable effectiveness in water treatment. In general, COFs can be constructed by the interfacial polymerization (IP) between a C2 symmetry monomer with para-position reaction groups and a C3, C4 and C6 symmetry functionalized monomer. The constrained availability of para-position monomers limits the diversity of COFs synthesis options, necessitating exploration into non-para-position alternatives. Herein, 2,4,6-triformylphloroglucinol (Tp) and ortho-position monomer o-phenylenediamine (OPD) are employed to fabricate a composite membrane featuring COFs with a special trefoil-like structure by interfacial polymerization method. The optimal OPD-Tp COFs/Nylon nanofiltration (NF) membrane has 99.8 % rejection for CR and only 3.2 % rejection for NaCl. Meanwhile, the pure water permeation flux is 132 L m−2 h−1 bar−1. This study shows the significant potential for dye/salt separation of the prepared COFs composite NF membrane and broadens the monomer selective range for the COFs membrane fabrication.