Construction of nanochannels with a delicate structure in nanocomposite membranes has emerged as a promising way to realize selective permeation, but is always stumbled by the organic-inorganic incompatibility and poor nanofiller dispersion. As such, much effort focuses on introducing weak noncovalent or strong covalent interactions by tailoring the composition of nanofiller surface. However, too weak or too strong interfacial interactions may lead to unfavorable interfacial structures with inefficiency for ion/organic molecule separation. Herein, inspired by the metal-fortified adhesion phenomenon of marine mussels, we developed a facile interfacial polymerization approach mediated by moderate catechol-TiIV coordination interactions to fabricate TiO2-polyarylate (PAR) thin-film nanocomposite (TFN) membranes with selective interfacial nanochannels. Tannic acid (TA), a polyphenol rich in pyrogallol groups, was selected as the aqueous monomer with tetrabutyl titanate (TBT) in organic solution as the TiO2 precursor. TA could partially chelate with Ti-IV, control the sol-gel reaction and generate homogeneously dispersed TiO2 nanoparticles (NPs) during membrane formation. The residual catechol/pyrogallol groups in the PAR matrix can further form moderate catechol-TiIV coordinates during water compaction, constructing interfacial nanochannels with tunable structures (e.g. size and connectivity) spontaneously. The permeation of water and ions was facilitated, leading to an enhanced water flux as well as superior ion/organic molecule selectivity. Meanwhile, the TFN membrane showed a good long-term operational stability for dye/salt separation. Since the catechol groups can coordinate with various metal-based materials, this approach is applicable to tailor the organic-inorganic interfaces for a broad range of TFN membranes.