研究目的
To design and synthesize three novel cadmium-based metal–organic frameworks (MOFs) using naphthalene diimide (NDI) derivatives and different second dicarboxylic acid ligands, and to explore their structural properties, photochromic behaviors, and the relationship between interpenetrating packing and photoresponse efficiency.
研究成果
The synthesis of three Cd-MOFs with different interpenetrated frameworks (5-fold for FJU-67 and FJU-68, 4-fold for FJU-69) demonstrates that the shape and size of second dicarboxylic acid ligands significantly influence the framework structure. FJU-67 and FJU-69 exhibit reversible photochromism due to photoinduced radical generation from NDI units, with interpenetrating packing affecting the efficiency of electron transfer reactions. The findings provide insights into designing photoresponsive MOFs and understanding structure-property relationships, suggesting potential applications in optoelectronics such as optical switching and information storage. Future work could explore a wider range of ligands and conditions to optimize photochromic properties.
研究不足
The study is limited to specific Cd-MOFs with NDI and dicarboxylic acid ligands; other metal ions or ligands were not explored. The photochromic behavior was only observed in FJU-67 and FJU-69, not in FJU-68 or the free H2NDI ligand. Structural changes during photochromism were not detected by PXRD, indicating possible limitations in sensitivity. The experiments were conducted in solid state and air, which may not represent all environmental conditions. Thermal stability varied among the compounds, with FJU-68 showing lower stability due to the amino group.
1：Experimental Design and Method Selection:
The study involved synthesizing three Cd-MOFs (FJU-67, FJU-68, FJU-69) via solvothermal reactions using Cd(NO3)2·4H2O, H2NDI ligand, and different second dicarboxylic acids (H2BDC, NH2-H2BDC, H2NDC) in water/DMF mixtures at 120°C for 2 days. Structural characterization was performed using single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), solid-state UV-vis spectroscopy, luminescence spectroscopy, and electron spin resonance (ESR) spectroscopy to analyze photochromism and related properties.
2：Sample Selection and Data Sources:
The samples were synthesized crystals of FJU-67, FJU-68, and FJU-69, with purity confirmed by PXRD matching simulated patterns. Data were collected from these synthesized materials.
3：List of Experimental Equipment and Materials:
Equipment included a PANalytical X'Pert3 powder diffractometer for PXRD, Thermo Nicolet 5700 FTIR instrument, METTLER TGA/SDTA 851 thermal analyzer, Perkin Elmer Lambda 950 UV-vis spectrometer, Dual-FL-800 luminescence spectrometer, Bruker ELEXSYS E500 EPR spectrometer for ESR, and SuperNova single-crystal diffractometer for SCXRD. Materials included Cd(NO3)2·4H2O, H2BDC, NH2-H2BDC, H2NDC, H2NDI ligand, DMF, methanol, and other reagents from Shanghai Chemical Reagent Co.
4：Experimental Procedures and Operational Workflow:
Synthesis involved ultrasonication of reactant mixtures, heating in Teflon-lined bombs, crystal collection, washing, and preservation. Characterization steps included data collection for structural analysis, thermal stability tests, photoirradiation with a 300 W xenon lamp for photochromism studies, and measurement of UV-vis, luminescence, and ESR spectra before and after irradiation.
5：Data Analysis Methods:
Structural data were refined using Olex2 with Superflip and ShelXL. Kinetic rate constants for photochromism were calculated using first-order rate equations. Data analysis involved software like Mercury V1.4 for PXRD simulation, PLATON for void volume calculation, and TOPOS 4.0 for topological analysis.
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