Polyoxometalate-Based MOF as a Highly Sensitive and Stable X-ray Detector for Imaging

Polyoxometalate-based metal-organic frameworks (POMOFs) show potential application prospects in the field of X-ray detection in recent years. However, it is still unclear how to effectively separate X-ray-induced charge carriers through the effective connection between polyoxometalates (POMs) and metal-organic frameworks (MOFs) due to their current infancy research status. Here, we designed and fabricated a novel POMOF BW₁₂-Cu^II-MOF-based X-ray detector for stable and sensitive X-ray detection and imaging. The Cu─O coordination bonds between [BW₁₂O₄₀]^5- and [Cu(2,2'-bipy)₂]²⁺ in the structure of BW₁₂-Cu^II-MOF are not only conducive to charge transfer between anion and cation, resulting in a high hole carrier mobility (μ_h) of 4.80 cm² V^-1 s^-1, but also effectively reduce ion migration and dark current simultaneously, which causes a small dark current drift as low as 1.2 × 10^-18 A cm^-1 V^-1 s^-1. Finally, the fabricated BW₁₂-Cu^II-MOF wafer device shows excellent X-ray detection performances, yielding a high sensitivity of 9832 µC Gy_air ^-1 cm^-2 with the lowest detectable dose rate of 120 nGy_air s^-1 at an electric field of 200 V mm^-1 under 80 kV X-ray irradiation. Furthermore, the constructed POMOF BW₁₂-Cu^II-MOF as a potential candidate for X-ray detection also exhibits good X-ray imaging capability and long-term operational stability without any encapsulation exposed to the air for 6 months.