Fully Conjugated Three-Dimensional Thiazole-Based Covalent Organic Framework Exhibiting Hierarchical Microtubular Architecture

In this work, we report the synthesis of a pseudotetrahedral cyclooctatetraene building block based on a thiazole heterocycle (COTz(CHO)4). The development of this building block required a challenging and carefully optimized synthetic strategy and represents a significant advance in the field of fully conjugated three-dimensional organic materials, as it constitutes one of the first examples of a thiazole-based heterocycle incorporated into three-dimensional frameworks. Polycondensation with p-phenylenediamine affords a highly crystalline covalent organic framework (COF) with permanent porosity, as confirmed by Rietveld refinement. The resulting material exhibits a high surface area and significant micropore volume. Morphological characterization by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) reveals a microtubular architecture. Furthermore, broad UV–vis absorption, strong photoluminescence, and an optical band gap of approximately 2.0 eV render the COTz-1P COF a promising candidate for future optoelectronic and photonic applications.