同构稀土金属-有机框架材料对离子型染料的吸附及光降解研究

Adsorption and photodegradation of ionic dyes by isomorphic rare earth metal-organic framework materials

以氨基化3,3′,5,5′-三联苯四羧酸(NH_(2)-H_(4)TPTC)为配体与稀土金属盐[Ho(NO_(3))_(3)·6H_(2)O、Er(NO_(3))_(3)·6H_(2)O]反应得到两个同构稀土金属-有机框架材料(MOFs)Er-NH_(2)-TPTC和Ho-NH_(2)-TPTC,两种MOFs材料在250℃以下具有良好的稳定性。选择不同类型的离子染料,并用所合成的材料进行吸附和光催化降解有机染料实验。结果表明:Er-NH_(2)-TPTC和Ho-NH_(2)-TPTC对离子型染料吸附效果优于中性染料,在光催化后对各类有机染料降解效果均得到提升。由于受染料分子尺寸的影响,两个同构稀土MOFs对小分子阳离子染料甲基蓝去除率可达99%,而对分子尺寸较大的阳离子染料罗丹明B降解效率最低,仅分别达到47%和73%。光催化降解的机理研究表明,降解过程中产生·O_(2)^(-)和·OH活性物质,此类自由基的产生有助于提高光催化降解效率。

Two isomorphic rare earth metal-organic framework materials(MOFs),Er-NH_(2)-TPTC and Ho-NH_(2)-TPTC,were obtained by the reaction of aminated 3,3′,5,5′-tribiphenyl tetracarboxylic acid(NH_(2)-H_(4)TPTC)as ligands with rare earth metal salts[Ho(NO_(3))_(3)·6H_(2)O and Er(NO_(3))_(3)·6H_(2)O].The two MOFs had good stability below 250℃.Different types of ionic dyes were selected,and the adsorption as well as photocatalytic degradation of the organic dyes were carried out with the synthesized materials.The results showed that Er-NH_(2)-TPTC and Ho-NH_(2)-TPTC exhibited better adsorption effects for ionic dyes than neutral dyes,and the degradation effects of various organic dyes were improved after photocatalysis.Due to the influence of dye molecular size,the removal efficiency of two isomorphic rare earth MOFs for small molecule cationic dye methyl blue could reach 99%,while the degradation efficiencies for larger cationic dye Rhodamine B were the lowest,reaching only 47% and 73%,respectively.The mechanistic studies of photocatalytic degradation revealed that·O_(2)^(-) and·OH active substances were produced during the process of degradation,and the generation of such radicals was helpful to improve the photocatalytic degradation efficiency.