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 mu C 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.