Chemical Research in Chinese Universities ›› 2026, Vol. 42 ›› Issue (5): 1461-1469.doi: 10.1007/s40242-026-6161-6

• Research Articles • Previous Articles     Next Articles

Polymeric Templates Enhancing the Quality of Two-dimensional Covalent Organic Framework Films Prepared on Water Surface

WANG Linna, LI Shuang, LIU Kejun, CHI Lifeng   

  1. State Key Laboratory of Bioinspired Interfacial Materials Science, Institute of Nano & Functional Materials, Soochow University, Suzhou 215123, P. R. China
  • Received:2026-07-02 Accepted:2026-08-02 Online:2026-10-01 Published:2026-09-24
  • Supported by:
    This work was supported by the Program of Collaborative Innovation Center of Suzhou Nano Science & Technology, China, the ‘111’ Project, the Program of Suzhou Key Laboratory of Surface and Interface of Intelligent Matter, China, the Program of Innovative Center for Molecular Science of Surface and Interface at Soochow University, China, the Gusu Innovation and Entrepreneurship Talent Program Major Innovation Team (No. ZXD2023002), the National High-Level Overseas Talent Program, China (No. KS21400126), the Surface and Interface Synthetic Chemistry Project, China (No. ZXP2025057), the Jiangsu Distinguished Professorship Fund, China (No. SR21400225), and the Research Start-up Fund, China (No. NH21400525).

Abstract: Air-water interfacial polymerization is an emerging route to crystalline 2D covalent organic framework (COF) thin films, which can be highly influenced by surfactants used to guide crystal growth. Here we screen six surfactant-like soft templates under identical Schiff-base conditions. Poly(acrylic acid) (PAA) and perfluoropolyether (PFPE)-OH deliver highly continuous polycrystalline films, whereas the other four anionic small-molecule surfactants produce fragmented islands or films with limited long-range order. Multi-scale characterization of 2D COF films resolves a tetragonal lattice with face-on orientation and atomically resolved square pores. Raman spectroscopy identifies a crystallinity-sensitive peak at 1562 cm-1, assigned by density-functional-based tight-binding (DFTB) to a Raman-active, IR-silent free-base porphyrin skeletal mode. This peak is weak or absent in small-molecule-templated films and provides a bench-scale crystallinity marker specific to porphyrin-node 2D COFs that retain local centrosymmetry. Atomic force microscopy (AFM) deep indentation on suspended Si3N4 membranes (1 μm radius) probes intra-domain mechanics, and the measured moduli (309—613 MPa across surfactants) are consistent with the film-quality hierarchy. The results suggest that a polymeric surfactant backbone, which creates a continuous interfacial template, plays a major role in 2D COF film continuity; intra-domain stiffness is largely independent of macroscopic film continuity. The mechanism, by which polymeric templates outperform small-molecule surfactants remains to be fully elucidated.

Key words: 2D covalent organic framework, Air-water interface, Surfactant template, Raman spectroscopy, AFM nanoindentation