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通过Zn~(2+)和1,3,5-三苯甲酸(H_3BTB)配体反应获得一种新型的四重互穿的金属有机框架结构(MOF)1。单晶体结构分析表明这是一种由中性N,N-二甲基甲酰胺(DMF)分子和H_2NMe_2~+阳离子沿b轴密封于通道的三维(10,3)网状阴离子框架结构。交流阻抗测试显示该结构的导电性能具有特殊温度依赖性。其电导值在20℃下为0.36×10~(-6)S·cm~(-1),随着温度升高导电能力迅速增大,160℃达到最大值2.24×10~(-5)S·cm~(-1),继续升高温度,导电能力开始下降。分子动力学(MD)模拟和介电性质测量表明,这种特殊温度依赖的导电性能是来自于随温度升高H_2NMe_2~+阳离子迁移增强以及DMF挥发的协同效应。0.20 V的传输能垒接近于质子导电性能。研究表明:MOFs孔对H_2NMe_2~+的限制作用是获得电子材料的一种潜在理想方法。同时,在1中发现一种有趣的荧光现象,发射峰位置比在H_3BTB配体中更加蓝移。密度泛函理论(DFT)计算揭示这是由于在1中,配体BTB~(3-)的离域π键结构破坏,禁带宽度增大所致。
A novel quadruple interpenetrating metal-organic framework (MOF) 1 was obtained through the reaction of Zn 2+ and 1,3,5-tribenzoic acid (H_3BTB) ligands. The single crystal structure analysis shows that it is a three-dimensional (10,3) reticular anion framework structure with N, N-dimethylformamide (DMF) molecule and H_2NMe_2 ~ + cation sealed along the b axis in the channel. AC impedance tests show that the conductivity of the structure has a special temperature dependence. The electrical conductivity of 0.36 × 10 ~ (-6) S · cm ~ (-1) at 20 ℃ increased rapidly with increasing temperature and reached the maximum at 2.24 × 10 -5 S · Cm ~ (-1), continue to increase the temperature, conductivity began to decline. Molecular dynamics (MD) simulations and dielectric properties measurements show that this particular temperature-dependent electrical conductivity results from the synergistic effect of enhanced H 2 NMe 2 + cation migration and DMF volatilization with increasing temperature. The transfer barrier at 0.20 V is close to the proton conductivity. The results show that the limiting effect of MOFs on H_2NMe_2 ~ + is a potential ideal method for obtaining electronic materials. At the same time, an interesting fluorescence phenomenon was found in 1 with a more blue-shifted emission peak position than in the H_3BTB ligand. Density functional theory (DFT) calculations reveal that this is due to the disruption of the delocalized π-bond structure of BTB ~ (3-) and the increase of the forbidden band width.