Crystalline Covalent Organic Frameworks from Triazine Nodes as Porous Adsorbents for Dye Pollutants

[Image: see text] The development of covalent organic frameworks (COFs) with nodes and spacers, designed to maximize their functional properties, is a challenge. Triazines exhibit better electron affinity than benzene-based aromatic rings; therefore, structures based on 1,3,5-substituted triazine-centered nodes are more stable than those from 1,3,5-benzene-linked COFs. Compared to COFs prepared from flat, rigid sp(2) carbon-linked triazine nodes, the O-linked flexible tripodal triazine-based COF demonstrates several unpredictable properties such as an increase in crystallinity and cavity size. In this study, the COF prepared from O-linked flexible 2,4,6-tris(p-formylphenoxy)-1,3,5-triazine serves as an excellent absorbent for removing methylene blue from water. Our results demonstrate that COF is highly stable in water and functions as a robust adsorbent. Its adsorption isotherm is consistent with the Langmuir model and its adsorption kinetics follows a pseudo-second order model. Moreover, the COF was characterized using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, solid-state ultraviolet–visible spectroscopy, and X-ray diffraction. It exhibited permanent porosity, a high specific surface area (279.5 m(2)·g(–1)), and was chemically and thermally stable. Photophysical studies revealed that the COF exhibits a low bandgap energy value of 3.07 eV, indicating its semiconducting nature.