Quantitative Assessment of Crystallinity and Stability in β-Ketoenamine-Based Covalent Organic Frameworks

The design and synthesis of covalent organic frameworks (COFs) with high chemical stability pose significant challenges for practical applications. Although a growing number of robust COFs have been developed and employed for a broad scope of applications, the assessment of COF stability has primarily relied on qualitative descriptions, lacking a rational and quantitative assessment. Herein, a novel assessment method is presented that enables visual and quantitative depiction of COF stability. By analyzing the PXRD patterns of chemically stable beta-ketoenamine-based COFs (KEA-COFs), two crystallinity-dependent parameters are identified, the relative intensity (I2 theta rel) and the relative area (A2 theta rel) of the main peak (2 theta), which are expected to establish a standardized criterion for assessing COF crystallinity. Based on these parameters, the crystalline changes after stability tests can be visually presented, which provides a rational and quantitative assessment of their stability. This study not only demonstrates the remarkable chemical stability of KEA-COFs, but also provides valuable insights into the quantitative evaluation of COFs' crystallinity and stability.