High Resistivity and Low Defect Covalent Organic Frameworks for Highly Stable and Low Dose X‐Ray Detection

ABSTRACT Direct x‐ray detection technology has long been constrained by trade‐offs between the extracted charge‐carrier signal and mobile‐metal‐ion noise under applied electric fields in conventional semiconductor materials. Here, we report the first demonstration of a low‐defect covalent organic framework (COF)‐based direct X‐ray detector, employing COF366‐M (M = Co, Cu) as the active layer. By incorporating metal ions into a porphyrin‐centered crystalline framework linked through multiple coordinate bonds, COF366‐M enhances x‐ray attenuation while effectively preventing ion migration with negligible current drift of ∼10 −18 A·cm −1 ·V −1 ·s −1 under the operating electric fields. The highly ordered nanochannels in COF366‐M exclude unintended ion doping and exhibit high resistivity along with a low defect level suitable for x‐ray detection. The addition of carbon nanotubes (CNTs) further enhances electron‐hole separation and creates charge‐transport pathways. The device achieves a high sensitivity of up to 11,784 µC·Gy −1 ·cm − 2 , a low detection limit of 39 nGy·s −1 , and excellent operational stability, with no degradation after a high cumulative x‐ray dose of 148 Gy. Moreover, the fully environment‐friendly composition ensures intrinsic environmental friendliness. This work not only validates COFs as a promising platform for high‐performance, stable, and green x‐ray detection, but also provides a molecular‐level paradigm for designing next‐generation low‐dose radiation sensing materials.