Efficient X-ray Detection of Polyoxometalates@Metal–Organic Frameworks Based on Host–Guest Electron Transfer

Semiconductive metal–organic frameworks (MOFs) have attracted conspicuous interest in X-ray detection. The host–guest strategy has been proven to be an effective means to improve the performance of MOF-based semiconductors. However, introducing a novel guest that combines carriers' regulating ability and X-ray absorption enhancement has not been explored. Herein, two polyoxometalates (POMs) with electron-rich and element-heavy are introduced into MOFs to architect host–guest structures applied for X-ray detection. Two POMs@MOFs (1 and 2) both can convert X-ray photons to recordable electrical signals. Detector 1 shows a high photocurrent profiting from its stronger exciton dissociation dynamic, therefore exhibiting a high sensitivity of 73.98 μC Gy–1 cm–2. With the high quality of PW12O403–, detector 2 shows an ultrahigh X-ray absorption, resulting in high on/off ratio and low detection limit. Moreover, the electron transfer mechanism from POMs to Cu(II) is substantiated by using spectroscopy and theoretical calculations.