General Synthesis of Inverse Opal Covalent Organic Framework Photonic Crystals

Abstract

Constructing highly crystalline inverse opal covalent organic framework photonic crystals (IO COF PhCs) remains challenging due to the incompatibility between the spatial confinement required for inverse opal replication and the synthesis process of COFs. Inspired by the semi-solid chitin infiltration and confined solidification process in beetle photonic architectures, a solvent-free template-assisted melt pressing (STAMP) strategy is developed for the general synthesis of crystalline IO COF PhCs. The quasi-solid precursor state facilitates efficient template infiltration while remaining reactive for COF crystallization, affording ordered macroporous photonic architectures within 3 min. This strategy is broadly applicable to a library of 16 COFs spanning β-ketoenamine, hydrazone, imine, and imide linkages, yielding decimeter-scale monoliths with designable structural colors across the visible spectrum. By integrating periodic macroporosity, permanent framework porosity, and photonic functionality into one material platform, the resulting IO COF PhCs enable cross-scale programmable optical encoding and visually self-reporting adsorption. The application potential of IO COF PhCs is demonstrated for biomimetic anti-counterfeiting patterns and structural-color-indicated Au capture. This work establishes a general route toward crystalline IO COF PhCs and provides a versatile platform for coupling molecular functionality with photonic regulation in advanced smart materials.