BiOBr photocatalysts were prepared by changing the solvent and synthesis method. SEM, XRD and BET characterization shows that the sample prepared in high-viscosity solution by precipitation method has tremella-like microstructure, with smaller size and higher surface area. Among them, the BiOBr prepared in glycerol solution (GR-P) has the highest surface area of 113.8 m 2 ⋅ − 1 . XRD also indicates that the GR-P has much more exposed (110) facets than other samples. The Rhodamine B degradation tests show that the GR-P has the best activity on both deethylation and aromatic ring destruction steps, indicating that the exposed (110) facets promote the degradation process.
Dan Lin,Jiamin Zhong,Shaomin Ji,Zhanxiang Yuan,Longjiang Xing,Qin He,Haoli Zhang,Yanping Huo
Movement of molecules are always affected by the surrounding solvent molecules , so solvents have an essential effect in triplet-triplet annihilation (TTA) upconversion. In this article, the TTA upconversion system with Diiodo-BODIPY ( MBDP-2I ) as sensitizer and perylene as acceptor in six solvents of differing viscosity were investigated (toluene, 1,4-dioxane and four high viscosity phthalate ester solvents DMP, DBP, DNOP and DOP). The upconversion efficiency was positively correlated with the solvent viscosity . Among the six solvents, the highest upconversion quantum efficiency of 9.59% was observed in high viscosity DOP (η = 72.4 mPa s), almost 1.5 times higher than that in 1,4-dioxane (η = 3.2 mPa s, Φ UC = 6.36%). The efficient upconversion was attributed to the long-lived triplet excited states of MBDP-2I , efficient fluorescence quantum yield of perylene and efficient TTA in high viscosity phthalate esters solvents. The mechanism underlying the highly efficient TTA upconversion in the high viscosity phthalate esters solvents was investigated by solvent cage effect. In addition, significant room temperature phosphorescence of MBDP-2I at 765 nm was observed in the viscous phthalate esters solvents.
Xiaojuan Li,Qiongyao Ning,Jiaqi Yao,Sitong Long,Jichuan Huo,Yi He,Rui Liu
The interlayer shifting of two-dimensional (2D) covalent organic frameworks (COFs) is a critical issue affecting their sorption and catalytic properties. However, current analytical tools often measure static and averaged stacking properties from bulk samples, restricting a comprehensive understanding of the interlayer shifting process in individual 2D COFs. Here, we report real-time dynamic imaging of the solvent exchange-induced interlayer shifting in single 2D COFs using in situ dark-field optical microscopy (DFM). The increase in pore size from quasi-AB stacking to AA stacking in triphenylbenzene (TPB)–terephthaldehyde–COF and TPB–dimethoxyterephthaldehyde–COF in organic solvent and water facilitates the accommodation of more guest molecules, leading to a higher scattering intensity. By using the grayscale intensity of DFM images as a quantitative indicator, we visually observe that the solvent exchange-triggered interlayer shifting dynamics not only exhibits a significant particle-to-particle heterogeneity but also is sensitive to the solvent viscosity and interlayer interaction strength of 2D COFs. Moreover, theoretical simulations elucidate that this interlayer shifting process is governed by crystal stacking energies and follows a thermodynamically preferred pathway during the water-to-organic exchange process. This imaging methodology provides a useful way for direct observation of solvent exchange-induced interlayer shifting in single 2D COFs and understanding its dynamics.
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