Efficient Direct X‑ray Detection and Imaging Based on a Lead-Free Electron Donor–Acceptor MOF

Metal–organic frameworks (MOFs) have recently
gained extensive
attention as potential materials for direct radiation detection due
to their strong radiation absorption, long-range order, and chemical
tunability. However, it remains challenging to develop a practical
MOF-based X-ray direct detector that possesses high X-ray detection
efficiency, radiation stability, and environmental friendliness. The
integration of donor–acceptor (D–A) pairs into crystalline
MOFs is a powerful strategy for the precise fabrication of multifunctional
materials with unique optoelectronic properties. Herein, a new lead-free
MOF, Cu2I2(TPPA) (CuI-TPPA, TPPA
= tris[4-(pyridine-4-yl)phenyl]amine), with a 6-fold interpenetrated
structure is designed and synthesized based on the electron donor–acceptor
strategy. CuI-TPPA has a large mobility-lifetime (μτ) product of 5.8 × 10–4 cm2 V–1 and a high detection sensitivity
of 73.1 μC Gyair–1 cm–2, surpassing that of commercial α-Se detectors.
Moreover, the detector remains fairly stable with only a 2% reduction
in photocurrent under continuous bias irradiation conditions with
a total dose of over 42.83 Gyair. The CuI-TPPA/poly(vinylidene fluoride) flexible composite X-ray detector films
are successfully manufactured with different thicknesses. Through
multifaceted assessments, the optimal thickness is found with a high
detection sensitivity of up to 143.6 μC Gyair–1 cm–2. As proof-of-concept, 11 ×
9 pixelated X-ray detectors are fabricated on the same composite film
to realize X-ray direct imaging. This work opens up potential applications
of MOFs in environmentally friendly and wearable devices for direct
X-ray detection and imaging.