Solid-State Hot-Pressing Strategy Breaks Scalability and Monolithic Shaping Barriers for Covalent Organic Frameworks
Covalent organic frameworks (COFs) are porous crystalline materials assembled from organic building blocks via strong covalent bonds, offering well-defined pores, high surface area, and tunable properties for applications in gas storage, separation, catalysis, sensing, and energy conversion. However, conventional solvothermal synthesis requires high temperatures, long reaction times, and complex procedures, hindering scalability and increasing costs. Additionally, COFs are typically obtained as microcrystalline powders, limiting their direct use in flow processes. To overcome these barriers, a novel solid-state hot-pressing method was recently reported, enabling rapid synthesis of COF platelets with high crystallinity and porosity. This method involves applying pressure and heat simultaneously, reducing the energy barrier for monomer reactions and facilitating layer growth and stacking, as confirmed by density functional theory and molecular dynamics simulations. The approach demonstrated versatility by synthesizing 15 distinct COFs, including imine-, hydrazone-, β-ketoenamine-, and imide-linked frameworks, a three-dimensional COF (COF-300), and a mixed-monomer COF, all within 0.5–5 minutes. Notably, a free-standing COF platelet of 200 cm² was fabricated, showcasing scalability. This strategy addresses the trade-offs among synthetic convenience, product quality, environmental impact, and scalability, positioning COFs for commercial viability.