RESUMO
The specific stacking mode of D/A blocks is often considered to largely determine the physicochemical properties of cocrystals. However, this rule may fail when encountering a large degree of (integer or near-integer) charge transfer situations. Herein, we explore the extensive correlations between the possible smallest structural units, stacking modes, and near-infrared photothermal conversion (NIR-PTC) properties of F4TCNQ-based cocrystals with typical features of integer-charge-transfer. Surprisingly, these cocrystals with distinct stacking modes display analogous D-A interactions, broad red-shift absorption, ultrafast (1-3 ps) relaxation dynamics of excited states, and excellent NIR-PTC properties. This supports that the resulting "D+A-" ion pairs from integer-charge-transfer may serve as the primary structural units beneath the secondary stacking modes to dominate the property of cocrystals. The stacking modes play an important but only secondary role. This work provides new insights into the structure-dynamics-property correlations and modular design of organic cocrystals for PTC and other applications.
RESUMO
Notably, the intermolecular charge transfer between pyrene (Py) and benzophonenes (BPs) can significantly enhance the quantum yield of the triplet state of Py, which will convert Py from a fluorescence molecule to a phosphorescence molecule. The intermolecular charge transfer is confirmed by steady-state and time-resolved spectroscopy and theoretical study. Based on these foundations, Py is doped into BPs systems and a large Stokes-shift organic room temperature phosphorescence (ORTP) is observed. By using different benzophenone derivatives, a series of host-guest ORTP materials with different luminescent properties adjusted by intermolecular charge transfer features are developed. Fortunately, these host-guest ORTP systems from benzophenone derivatives and pyrene are readily fabricated, and the red gradient color lasting as long as 3 s is observed after removing UV excitation. This host-guest charge transfer strategy plays an important role in the mechanism of the luminous type shift. Our strategy paves the way to design ORTP materials conveniently and apply these materials in encryption and temperature alarm device.
RESUMO
A polyoxometalate acid can be encapsulated into a metal-organic framework to construct a novel kind of solid-acid catalyst. In this work, the two-step method -high-temperature preparation of Zr6O4(OH)4(CH3COO)12 and low-temperature self-assembly-has been adopted to synthesize the PW12@UIO-66 composite (PW12 = H3PW12O40; UIO-66 = Zr6O4(OH)4(OOC-C6H4-COO)12). The as-synthesized PW12@UIO-66 composite exhibits highly crystalline, good octahedron morphology, large specific surface area (1960 m2 g-1) and high thermal stability (>500 °C), which clearly demonstrates the potential as a solid-acid catalyst. Additionally, the PW12@UIO-66 composite may be accomplished with 85% utilization of H3PW12O40 and 95% yield through this synthetic procedure. The performances of the PW12@UIO-66 composite are investigated by catalyzing the simultaneous transesterification and esterification of soybean oil into biodiesel. Under the optimal conditions, the conversion of the soybean oil into biodiesel would exceed 90% over the as-synthesized PW12@UIO-66 composite. As the crucial indexes for industrial prospects, the recycling and life experiments were surveyed. After 10 times recycling and 4 weeks, the structure and performance of the PW12@UIO-66 composite remained unchanged and in the meantime the PW12@UIO-66 composite still maintained a high activity to convert soybean oil into biodiesel.
