Engineering Solute–Solvent Interactions for the Synthesis of Covalent Organic Polymer Nanosheets

Covalent organic polymer (COP) nanosheets hold great potential for widespread applicability, but their fabrication remains challenging. Here, a dipole-moment-mediation strategy is reported to manipulate solute–solvent interactions, enabling the facile synthesis of COP nanosheets under ambient conditions. Three COPs with different morphologies are synthesized from three amine monomers with ascending dipole moment (Qd: 0.69 D, PDA: 1.46 D, VON: 2.37 D) and 1,3,5-triformylphloroglucinol (TP) in dimethyl sulfoxide (3.93 D). Combined with experimental results and quantitative analysis from DFT calculations, monomers with higher dipole moments generate stronger solute–solvent interactions. The strong solute–solvent interactions (−0.271 eV) significantly disrupt intermolecular interactions (−0.058 eV), suppressing 3D random aggregation in TP-VON, and facilitating in-plane anisotropic growth, producing laterally expanded nanosheets. The TP-VON nanosheets colloidal suspensions are cast into free-standing, continuous, and compact membranes with exceptional chemical stability, achieving a proton conductivity of 176.55 ± 4.31 mS cm⁻¹ (80 °C, 95% relative humidity) and tensile strength of 47.00 MPa after being doped with phosphoric acid. It is believed that this dipole-moment-mediation strategy opens a new paradigm for the synthesis of COP nanosheets.