N-heterocyclic carbenes incorporated in porous networks

可重复使用催化剂系统的研制和设计是绿色工艺工程中的一个关键问题。多相催化的概念通常可以实现催化剂的可回收利用，但金属浸出、催化剂中毒和催化剂劣化等因素往往限制了这种方法的适用性。Capone项目侧重于固定化非杂环卡宾的新概念。金属NHC物种最近被认为是一类用途特别广泛的新型催化剂，可用于在极其温和的条件下进行大量反应。这种NHC物种的固定化将允许一方面结合高催化活性，另一方面实现可回收利用。使用双功能卡宾前体，将通过自下而上的方法合成多孔性网络，将NHC作为多孔性材料的固有部分，而不是仅仅将其从预先形成的载体上嫁接。我们将重点阐述两类含有NHC物种的多孔材料：·亲水周期性介孔有机硅(PMOS)和·疏水有机聚合物网络在多相催化中的应用，反应介质和多相催化剂的极性可能是可取的。因此，PMO在水介质中的使用可能很有趣，而有机聚合物网络在使用有机溶剂时更有用。我们认为这些材料具有作为多相催化剂系统的巨大潜力，原因如下：i)所用载体的高孔隙率确保了固定化NHC物种的可获得性，ii)由于NHC通过双键紧密地结合到多孔网络中，催化剂的化学和形态稳定性应该得到极大的提高。

The elaboration and the design of re-usable catalyst systems is a key issue in green process engineering. The concept of heterogeneous catalysis often allows to achieve recyclable catalysts, but factors such as metal leaching, catalyst poisoning and catalyst deterioration often limit the applicability of this approach. The CAPONE project focuses on new concepts towards the immobilization of Nheterocyclic carbenes. Metallic NHC species recently appeared as a particularly versatile new class of catalysts for numerous reactions under extremely mild conditions. The immobilisation of such NHC species would allow to combine high catalytic activity on one side and recyclability on the other side. Using bifunctional carbene precursors, porous networks will be synthesized by a bottom-up approach featuring the NHC as inherent part of the porous material instead of just grafting it from a pre-formed support. We will focus on the elaboration of two types of porous materials bearing NHC species: • hydrophilic periodic mesoporous organosilicas (PMOs) and • hydrophobic organic polymer networks For applications in heterogeneous catalysis, the adjustment of the polarity of the reaction medium and the heterogeneous catalyst can be desirable. For this reason, the use of PMOs may be interesting in aqueous media, whereas organic polymer network are more useful when organic solvents are employed. We believe that these materials have great potential as heterogeneous catalyst systems for the following reasons: i) high porosity of the used supports that ensures accessibility of immobilized NHC species, ii) Chemical and morphological stability of the catalyst should be strongly enhanced due to the dense incorporation of the NHC into the porous network by the twofold-bonding.