A series of metal organic frameworks (MOFs) MDABCO (M = Co, Ni, Cu, Zn; DABCO = 1,4-diazabicyclo[2.2.2]octane) are utilized as catalysts for the bulk ring-opening polymerization of l -lactide. The catalytic activity varies in the order CuDABCO, NiDABCO < ZnDABCO, CoDABCO. By adding lactic acid, we unexpectedly observed enhanced catalytic activity. The combined use of lactic acid and ZnDABCO during polymerization results in a highly active polymerization system, along with the gradual change of MOFs structure caused by an increased acid concentration. Compared to related homogeneous fragments, such as zinc nitrate and 1,4-diazabicyclo[2.2.2]octane, ZnDABCO is found to afford highly isotactic polylactide, which would be ascribed to the unique structural properties of MOFs.
Achieving real-time, high-sensitivity radiation detection with stability and precision remains a critical challenge in medical diagnostics and radiation therapy. Here, we report the development of MDABCO-NH4(BF4)3 single crystals (SCs), a metal-free perovskite material with exceptional performance for both X-ray and charged particle detection. Large-scale MDABCO-NH4(BF4)3 SCs (15 × 13 × 5 mm3) were synthesized via a simple low-temperature solution method, achieving superior crystallinity with a full width at half-maximum (fwhm) of 0.0061°. The MDABCO-NH4(BF4)3 detectors exhibit high resistivity (1.31 × 1012 Ω·cm), low trap density (1.09 × 109 cm–3), and excellent charge transport properties ((μτ)h = 3.15 × 10–5 cm2·V–1). For α-particle detection, the MDABCO-NH4(BF4)3 detectors achieve a high energy resolution of 35.0% at 5.49 MeV and a fast response time of 5 ms, demonstrating single-particle sensitivity. For X-ray detection, MDABCO-NH4(BF4)3 detectors exhibit high sensitivity (13,529 μC·Gyabs–1·cm–2) and an ultralow detection limit (17.1 nGyair·s–1), significantly lower than the 5.5 μGyair·s–1 standard for active personal dosimeters used in regular medical diagnostics. The combination of superior charge transport properties with stability and high signal-to-noise ratio establishes MDABCO-NH4(BF4)3 SCs as a versatile material for real-time radiation monitoring and high-precision medical imaging applications.
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