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

ABSTRACT 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, [SiW 12 O 40 ] 4− , and H 4 BINDI 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 cm 2 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.