Maximizing Porosity and Water Sorption in Covalent Organic Frameworks via β‐Ketoenamine Linkages

Abstract Controlling the crystallinity and porosity of 2D covalent organic frameworks (2D COFs) is crucial for their applications in science and technology. Herein, the construction of 2D COFs, COF‐TP‐X, is reported using a multicomponent reaction strategy that introduces β‐ketoenamine linkages into isostructural imine‐linked COFs. This approach yields materials with exceptional crystallinity, stability, and tunable hydrophilicity. The integration of β‐ketoenamine linkages promotes intralayer planarity via NH⋯O hydrogen bonds and enhances π‐electronic conjugation within and between layers. By partially substituting (43 mol%) 1,3,5‐triformylbenzene with 1,3,5‐triformylphloroglucinol, an outstanding gravimetric surface area of 1,984 m² g⁻¹ and a pore volume of 0.8 cm³ g⁻¹ are achieved—a remarkable two‐fold increase compared to mono‐linker counterparts. Moreover, COF‐TP‐X exhibits an exceptional water uptake capacity of 0.70 g g⁻¹ (70 wt.%) and superior hydrolytic stability, as confirmed by over 200 cycles of water adsorption–desorption experiments. Furthermore, molecular simulations reveal the significant role of electrostatic interactions between β‐ketoenamine linkages in enhancing interlayer stacking and crystallinity. The findings provide key insights into COF design via a mixed‐linker strategy, representing a significant advancement in developing COFs with superior performance and paving the way for their industrial applications.