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

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.