Interfacial oligomer splicing toward 3D silicon-centered polyimine nanofilm for rapid molecule/ion differentiation

Abstract

3D porous organic polymers —renowned for rich interpenetrated, hierarchical pores and exceptional structural durability— showcase the potential for precise membrane-based separations. However, the challenge lies in processing these chemically stable polymers into a selective thin film under mild conditions. Herein, an interfacial oligomer splicing (IOS) approach via Schiff-base reactions is presented to create 3D silicon-centered porous polyimine (PPIn) nanofilms. The pre-synthesized oligomers from 4,4′,4″,4‴-silanetetrayltetrabenzaldehyde (TFS) and m-phenylenediamine (MPD) with high steric hindrance and hydrophobic character are precisely confined at the oil boundary, initiating IOS to yield an amorphous nanofilm on a Kevlar hydrogel surface. These silicon-centered 3D nanofilms exhibited an exceptional thermal and mechanical stability, while offering abundant low-resistance transport nanochannels. The nanofilm backbone, composed of rigid nonplanar aromatic skeleton and robust imine linkage, contributed to open and interpenetrated selective nanochannels, corroborated by both experimental and simulation and results. It was shown that 83-nm-thick PPIn nanofilms grown on the hydrogel achieved high-efficient molecule/ion differentiation, evident in excellent dye retention (>99.0 %), high NaCl permeation (92.8 %), and remarkable water permeability (74.3 L m⁻² h⁻¹ bar⁻¹). This study establishes an innovative IOS approach for fabricating silicon-centered 3D-POP membranes and underscores their potential for efficient molecule/ion differentiation.