金属有机框架纳米晶合成及在有机染料废水处理中的应用基础研究

Dirty water is the world's biggest health risk, and continues to threaten both quality of life and public health. China has become world factory in textile industry. Removing of dye contaminants from wastewater is most important. The adsorption of contaminant from liquid phase is one of environment-friendly treatments. Material with high specific surface area, which reasonably shows high adsorbability, is key for this strategy. As we all known, both Metal-Organic Frameworks (MOFs) and nanomaterial show exceptionally high specific surface area but through different way: high porosity and small size, respectively. Rational combination of these two distinguishing features will predictably get significant absorptivity, and will help to find new sorbent... MOFs have attracted a great amount of attention in the past two decades owing to their high porosity. Compared with their fascinating characteristics, such as gas storage, separation, sensing, catalysis, the use of MOFs in liquid-phase adsorption or separation is still at an early stage. The major hurdles are: (1) most MOF materials are unstable when exposed to water and (2) the complex behavior in the liquid phase. To the best of our knowledge, most of previous studies on dye capture by MOFs were focused on correlation between capability of dye molecules and MOF’s essential features, including high porosities, relatively heterogeneous surface, the nature of the framework metal ions , and potentially strong electrostatic interactions with the guest molecules. However, the effect of the size of MOFs crystals is relatively rare... The research will build a wonderful bridge between nanoscience and coordination chemistry. The special strategy arised from topological structure of MOFs will be designed to prepare nanocrystalline MOFs (nano-MOFs). It will be focused that small size effect on nano-MOFs in this project. Surface chemistry of nano-MOFs at the liquid–solid interface, equilibrium and dynamics of adsorption of dye will be discussed. The dye on surface of particles will prevent water to enter into the channel of MOFs when saturation adsorption is approached, leading to higher stability and flexibility for nano-MOFs. The weakness for MOFs that is unstable when exposed to water will be conquered. The smaller size of particles, the more surface adsorption will be achieved. The adsorption rate and equilibrium adsorption capacity of nanoparticles will increase significantly. It is believed that there's a plenty room in nano - MOFs.

吸附是解决有机染料污染水问题的关键步骤，大比表面积是提高吸附能力的核心。已知纳米材料通过减小粒径、金属有机框架(MOFs)通过增大孔体积拥有了大比表面积，因此本项目拟在纳米材料和配合物化学交叉领域中进行探索。将二者有机结合从制备纳米晶MOFs出发，设计出具有MOFs特色的纳米材料合成路线；讨论粒径对MOFs比表面积的影响，探索纳米晶MOFs优于块材的性质，发现MOFs领域的小尺寸效应；通过纳米晶大量的表面吸附，吸附饱和后，表面染料分子阻碍水分子对MOFs结构的破坏，解决MOFs在水溶液中不稳定的致命弱点；从拓扑性质、静电引力、官能团间作用等考察纳米晶MOFs吸附染料分子作用机制，获得通过简单过滤即可除去染料的快速且吸附量大的吸附剂；染料分子只是进入MOFs孔道的客体，将染料富集后可以方便地溶出实现染料的回收再利用。项目成果将为染料废水处理工业提供系统的实验基础。

纳米MOF（NMOF）可通过小尺寸效应和形貌控制在原有拓扑性能的基础上实现其功能化调控。然而，MOF的配位键本质以及大的晶胞参数使模板法等一些在纳米材料控制合成中常用的技术路线应用到制备NMOF时遇到障碍，制备10nm以下的NMOF已成为该领域研究的瓶颈问题。我们巧妙地运用了前驱体通过氢键网络所形成的金属有机凝胶，获得了5 nm的纳米金属有机框架 ( NMOF ) 材料，并证明了该材料因小尺寸而获得了额外的水稳定性、高的染料吸附速率或吸附量，阐明了吸附分子与框架作用而导致晶格收缩的微观本质。该工作因在NMOF研究中所取得的晶粒尺寸的实验突破，以封面文章形式发表在Nano Res杂志上。.污染物治理的重要性不言而喻，温室气体CO2的光催化还原备受关注。某些MOF不仅拥有高的CO2吸附量，而且对CO2具有强配合作用，使其在CO2光催化领域拥有良好的前景。另一方面，某些半导体如CdSe应用于光催化的优势在于带隙窄，容易被激发产生电子空穴对，是长波光催化剂的优秀备选材料。我们以光激发半导体产生电子空穴对，并利用MOF对CO2的吸附能力以及电子传输能力，避免电子空穴复合，使电子与CO2反应，从而获得了纳米半导体-MOF协同作用的高效光催化剂。