In this paper, the enhanced adsorption properties and mechanism of NH₂ functionalization titanium-based metal-organic frameworks (NH₂-MIL-125(Ti)) towards various organic dyes was investigated. First, MIL-125(Ti) and NH₂-MIL-125(Ti) were successfully synthesized and characterized. The as-prepared Ti-MOFs can be facilely magnetized by adsorbing Fe₃O₄ nanoparticles on their surfaces via a Lewis acid-base interaction. Then, three types of dye (cationic dye, anionic dye and vat dye) adsorption measurements show that the electrostatic interaction, π-π stacking interaction and pore filling all play important roles in the adsorption process of both Ti-MOFs in aqueous solutions. Particularly, the amino group in NH₂-MIL-125(Ti) can provide extra hydrogen bonding interaction towards target substances, which results in a stronger interaction force and a higher adsorption capacity than that of MIL-125(Ti). The adsorption kinetics and isotherm suggested the adsorption process of both Ti-MOFs towards methylene blue (MB) were better fitted to a pseudo-second-order kinetic and Freundlich isotherm model. The adsorption thermodynamic experiments demonstrated that adsorption of MB on both Ti-MOFs was spontaneous. However, their values of enthalpy and entropy were opposite, indicating that their adsorption processes were controlled by enthalpy and entropy effect, respectively.

本文研究了NH ₂官能化钛基金属有机骨架（NH ₂ -MIL-125（Ti））对各种有机染料的增强吸附性能和机理。首先，成功合成并表征了MIL-125（Ti）和NH ₂ -MIL-125（Ti）。可以通过路易斯酸-碱相互作用将Fe ₃ O ₄纳米粒子吸附在其表面上，从而将制备的Ti-MOF轻松磁化。然后，三种类型的染料（阳离子染料，阴离子染料和还原染料）的吸附测量结果表明，静电相互作用，π-π堆积相互作用和孔填充在两种Ti-MOF在水溶液中的吸附过程中均起着重要作用。特别是NH中的氨基₂ -MIL-125（Ti）可以与目标物质提供额外的氢键相互作用，与MIL-125（Ti）相比，具有更强的相互作用力和更高的吸附能力。吸附动力学和等温线表明，两种Ti-MOF对亚甲基蓝（MB）的吸附过程都更适合拟二阶动力学和Freundlich等温线模型。吸附热力学实验表明，MB在两种Ti-MOF上都是自发吸附的。然而，它们的焓和熵值相反，表明它们的吸附过程分别受焓和熵效应控制。