可溶性金属纳米簇的可控合成及其催化特性研究

Heterogeneous catalysis has become one of the most important catalytic technologies due to its facile separation and sustainable working ability. Compared to the traditional heterogeneous catalysts, ultrafine metal nanoclusters (< 2 nm) have excellent catalytic activity and selectivity. However, they are easy to aggregate owing to the high surface energy, and thus synthesizing ultrafine metal nanoclusters is challenging. In particular, considering the low dispersibility of traditional supports in liquid phase, there are still essential differences in dispersibility and catalytic activity between the supported metal nanoclusters and homogeneous catalysts. The project here proposes the discrete organic molecular cages with open skeletons as supports to construct high-performance soluble ultrafine metal nanoclusters possessing the advantages of both homogeneous and heterogeneous catalysts. The main objectives are to form ultrafine metal nanoclusters with controllable size, interface structures and solubility by optimizing the functional groups, pore size, pore structure and solubility of organic molecular cages as well as the methods for supporting metal nanoclusters, leading to enhancements in catalytic activity, selectivity and stability. The relationships between the size, structure, solubility and catalytic properties will be constructed by systematically investigating the controllable synthesis of organic molecular cage, metal nanoclusters as well as the unique catalytic performance of metal nanoclusters. Finally, this project will develop an innovative preparation technology for the soluble metal nanoclusters and the knowledge can be significant for the development of advanced catalysts with high activity, selectivity and stability.

多相催化因分离简单、可持续流水作业已成为一门重要的催化技术。与传统多相催化剂相比，超细金属纳米簇（< 2 nm）具有良好的催化活性和选择性，但其表面能极高，本身极易团聚，合成极具挑战性。特别是考虑到传统载体在液相中不能均匀分散，负载型金属纳米簇的分散性、催化活性与均相催化剂仍存在本质差别。本项目提出以具有开放骨架和离散结构的有机分子笼为载体构筑高活性可溶性超细金属纳米簇，实现均相催化和多相催化的统一。通过优化有机分子笼的官能团、孔径、孔结构、可溶性以及负载金属纳米簇的方法等优化超细金属纳米簇的尺寸、表界面结构、可溶性，从而提升金属纳米簇的催化活性、选择性和稳定性。通过系统研究影响合成有机分子笼、金属纳米簇的因素以及金属纳米簇的催化特性，建立尺寸、结构、可溶性等与催化特性的关系，开发出具有自主知识产权的金属纳米簇制备技术，为高活性、选择性、稳定性纳米催化剂的发展提供一定的理论依据。

随着各类清洁能源逐渐替代传统能源，人们对低能耗高效率的新催化技术的需求日益增大。多相催化因分离简单、节能已成为重要的一门催化技术。与传统多相催化剂相比，超细金属纳米簇（< 2 nm）具有良好的催化活性和选择性，但其表面能极高，本身极易团聚，合成极具挑战性。特别是考虑到传统载体在液相中不能均匀分散，负载型金属纳米簇的分散性、催化活性与均相催化剂仍存在本质差别。本项目提出以具有稳定分子骨架的有机分子笼为载体对金属纳米簇封装构筑高活性可溶性超细金属纳米簇，实现均相催化和多相催化的统一。项目研究团队基于硫杯芳烃的配位笼CIAC-108对金纳米粒子进行大小和位置控制的合成。通过优化有机分子笼的官能团、孔径、孔结构以及负载金属纳米簇的方法等优化超细金属纳米簇的尺寸、表界面结构、可溶性，从而提升金属纳米簇的催化活性、选择性和稳定性。当添加低浓度的Au前驱体时，实现了封装在CIAC-108腔中的小尺寸(1.3 nm)超细金纳米颗粒（Au NPs）。如果选择高浓度的Au前驱体，则在笼外围(Au/CIAC-108)会出现颗粒较大的Au NPs (4.7 nm)。对于这两种不同尺寸的Au NPs，更小尺寸的Au NPs具有更高的催化活性。CIAC-108的固有空腔具有控制Au NPs大小的能力，防止其聚集，并保持其在溶液中的良好稳定性的能力。配位笼中嵌入的Au NPs可以在甲醇和二氯甲烷混合溶液中作为均相催化剂，对硝基芳烃的还原和有机染料分解的催化有明显的增强，而在甲醇中可作为多相催化剂。本研究通过将超小型金属纳米团簇封装在配位笼中，为具有更高活性的纳米级催化剂的发展提供一定的借鉴价值和数据支撑。