Multiple Electron Transfer in Semiconductive Ternary D‐D'‐A Metal‐Organic Framework for Enhanced X‐Ray Detection and Imaging

Abstract Semiconductive metal–organic frameworks (MOFs) with donor–acceptor (D–A) characteristics have garnered attractive attention due to their capacity for separating and transferring photogenerated charges, making them promising candidates for high‐performance X‐ray detectors. However, the low charge transfer efficiency between the metal nodes and organic ligands limits the X‐ray‐to‐electricity conversion efficiency of these materials. Herein, an additional photoactive donor (D’) is introduced by incorporating a heavy atom‐containing polyoxometalate (POM) [α‐SiW ₁₂ O ₄₀ ] ⁴⁻ into a binary {[Ni·bcbp·(H ₂ O) ₂ ]·(H ₂ O) ₄ ·Cl} _n (Ni‐bcbp, bcbp: H ₂ bcbp·2Cl = 1,1′‐bis(4‐carboxyphenyl)(4,4′‐bipyridinium) dichloride) MOF, resulting in a semiconductive ternary D‐D'‐A framework {[Ni ₂ (bcbp) ₂ ·(H ₂ O) ₄ ·(DMA)]·(SiW ₁₂ O ₄₀ )} _n (SiW@Ni‐bcbp, DMA: dimethylacetamide). The obtained material features an unprecedented porous 8‐connected bcu‐net structure that accommodates nanoscale [α‐SiW ₁₂ O ₄₀ ] ⁴⁻ counterions, displaying uncommon optoelectronic responses. In contrast to binary Ni‐bcbp, the SiW@Ni‐bcbp framework exhibits distinctive photochromism and robust X‐ray responsiveness, which can be attributed to the synergistic effects of the electron reservoir and multiple photoinduced electron transfer originating from the POMs. As a result, the X‐ray detector based on SiW@Ni‐bcbp demonstrates a sensitivity of 5741.6 µC Gy _air ⁻¹ cm ⁻² with a low detection limit of 0.49 µGy _air s ⁻¹ . Moreover, the devices demonstrated the capability of producing clearness X‐ray images, providing a feasible and stable solution for constructing high‐performance direct X‐ray detectors.