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.