Regulating Energy Dissipation Pathways in Rare-Earth D-D'-A MOFs for High Sensitivity X-Ray Detection

Direct X-ray detectors are of great importance for high-performance X-ray imaging, yet semiconductive metal-organic framework (MOF)-based detectors remain limited by inefficient charge transport and additional energy loss during irradiation. Herein, we construct two isostructural ternary D-D'-A rare-earth polyoxometalate MOF single crystals, Tm-NDI-SiW and Eu-NDI-SiW, in which the rare-earth nodes, [SiW₁₂O₄₀]^4-, and H₄BINDI function as the donor (D), secondary donor (D'), and acceptor (A), respectively, enabling long-range charge-transfer channels and efficient carrier separation. Although the two crystals share the same framework architecture, Tm-NDI-SiW exhibits strongly suppressed rare-earth-related radioluminescence, accompanied by denser molecular packing and stronger donor-acceptor coupling, thereby reducing radiative energy dissipation and promoting charge collection. As a result, the Tm-NDI-SiW single-crystal detector delivers a sensitivity of 2616.9 µC Gy_air ^-1 cm^-2 and a µτ of 8.17 × 10^-5 cm² V^-1, approximately 2.0- and 1.9-fold those of Eu-NDI-SiW, respectively. Furthermore, incorporating Tm-NDI-SiW microcrystals into a PVDF matrix affords a flexible detector with an enhanced sensitivity of 2825.6 µC Gy_air ^-1 cm^-2 and enables 3 × 5 pixel X-ray imaging. These results show that regulating radioluminescence as a competing energy-dissipation pathway, together with promoting long-range charge transport, is an effective strategy for high-performance MOF-based direct X-ray detection.