Supercritical carbon dioxide as reaction medium: synthesis, catalytic properties and recovery of hybrids of amphiphilic macromolecules with metal nanoparticles

超临界流体表现出一系列不寻常的性质，这些性质可用于开发分离、化学反应或材料加工等领域的新反应。除了替代有毒工业溶剂的能力之外，超临界流体的主要兴趣在于可以在小的压力和温度变化下连续地将流体性质从液体调节到气体。可溶性过渡金属颗粒的尺寸为几个纳米的今天被认为拥有在许多重要的合成过程中的关键作用。然而，它们的受控制备、稳定化和催化反应后的回收仍然是关键挑战。本研究拟将金属纳米粒子制备并稳定在极性超支化的两亲性大分子核中。亲CO2壳提供在超临界二氧化碳（scCO 2）中的溶解度。通过直接在超临界CO2中合成来控制颗粒尺寸和形态，并将研究作为水介质中的替代方法与随后的壳结构。将在scCO 2中研究双键氢化和C-C偶联（Heck反应）的催化性能，并与有机溶剂中的催化进行比较。将研究通过改变二氧化碳介质的性质，特别是密度，从催化反应的产物中回收亲CO2聚合物/纳米颗粒混合物。这对于催化活性纳米颗粒的回收是特别令人感兴趣的，因为对胶体稳定性施加的压力很小。

Supercritical fluids exhibit a range of unusual properties which can be exploited for the development of new reactions in such fields as separation, chemical reactivity, or material processing. Beyond the capability of replacing toxic industrial solvents, the main interest of supercritical fluids is the possibility to tune continuously the fluid properties from liquid to gas with small pressure and temperature variations. Soluble transition metal particles with sizes of a few nanometers are recognized today to possess a crucial role in many synthetically important transfomations. However, their controlled preparation, stabilization and recovery after catalytic reaction remain key challenges. In the research proposed metal nanoparticles will be prepared and stabilized in the polar hyperbranched core of amphiphilic macromolecules. A CO2-philic shell provides solubility in supercritical carbon dioxide (scCO2). Particle size and morphology control by synthesis directly in scCO2, and as an alternative approach in aqueous media with subsequent construction of the shell will be investigated. The catalytic properties in hydrogenation of double bonds and in C-C coupling (Heck reaction) will be studied in scCO2, and compared to catalysis in organic solvents. Recovery of the CO2-philic polymer/nanoparticle hybrides from the products of a catalytic reaction by means of changing the properties of the carbon dioxide medium, particularly the density, will be investigated. This is of particular interest with respect to the recovery of catalytically active nanoparticles, as little stress on colloidal stability is imposed.