Earth abundant metal catalysts stabilized by porous N-doped carbon

近年来，稀土富集型催化剂成功地替代了稀有贵金属作为均相催化剂。可重复使用的纳米结构加氢和脱氢催化剂以丰富的可用金属为基础，在有机合成中具有广泛的应用范围，但开发的程度要小得多。主要的批评来自观察到，与贵金属相比，富含稀土的金属在纳米结构催化剂中的活性要低得多。聚合物基氮化硅和碳化硅材料结合了材料特有的特性，如热稳定性和耐腐蚀性，易于加工，可以在不同的有机溶剂中在低温下成型或结构化。在《Angewandte Chemie》、《自然通讯》(2x)和《自然催化》等四篇已发表的手稿中，金属-SiCN纳米复合材料作为可重复使用的催化剂的潜力和我们在3D-金属催化(多相)方面的专业知识已经被证明。在本项目中，我们计划展示与贵金属催化剂相比，纳米结构3D金属催化剂在活性和选择性方面的优势，并提出1.开发新型多孔N掺杂碳化硅载体和2.设计用于加氢和脱氢反应的活性和选择性3D金属催化剂。由于载体合成是开发新型高活性催化剂的基础，这两个目标具有很强的关联性。SiCN得到的金属纳米颗粒明显更小，活性更强，但高比表面的生成是一个问题。特别是小而活性的金属纳米颗粒的稳定性可以用载体中N原子的存在来解释。它们在合成和催化过程中通过配位稳定金属离子和团簇或颗粒，以抑制较大聚集体的生长。碳化硅更容易合成，因为先驱体聚合物对水解不敏感，可以产生更高的比表面。不幸的是，稳定非常小的和高活性的金属纳米团簇或颗粒的N原子并不存在。这些优点的结合将是多孔性的N掺杂碳化硅。初步工作支持这一假说。关于2.：在这个子项目中，我们感兴趣的是：a)钴催化的还原胺化反应，用于在温和的条件下合成伯胺；b)在容易加氢的官能团存在下的氰化物的加氢反应；以及c)迄今很少或从未使用过的3D金属的选择性(脱氢)催化剂的设计。

The replacement of rare noble metals by earth abundant metals has been demonstrated successfully for homogenous catalysts in recent years. Reusable and nano-structured hydrogenation and dehydrogenation catalysts, based on abundantly available metals, with a broad scope in organic synthesis have been developed to a much lesser extent. The main criticism arose from the observation that earth abundant metal are much less active in nanostructured catalyst in comparison to noble metals. Polymer based SiCN and SiC materials combine material specific characteristics such as thermal robustness and corrosion resistance with easy processing and possible shaping or structuring at low temperatures in diverse organic solvents. This easy processing also permits the synthesis of highly active catalysts.In four published manuscripts, in “Angewandte Chemie”, in “Nature Communication” (2x), and in “Nature Catalysis”, the potential of metal-SiCN nanocomposites as reusable catalysts and our expertise in 3d-metal catalysis (heterogeneous) have been demonstrated. In this project, we plan to show that nanostructured 3d-metal catalysts could be superior in activity and selectivity compared to noble metal catalysts and propose 1. the development of novel porous N-doped SiC supports and 2. the design of active and selective 3d-metal catalysts for hydrogenation and dehydrogenation reactions. Both aims are strongly linked since the support synthesis is the basis for developing novel highly active catalysts.Regarding 1.: SiCN and SiC have material specific advantages and disadvantages as porous supports for metal catalysts. SiCN gave significantly smaller and more reactive metal nanoparticles while the generation of high specific surfaces is a problem. The stabilization of especially small and reactive metal nanoparticles can be explained by the presence of N-atoms in the supports. They stabilize metal ions and clusters or particles via coordination during synthesis and catalysis to suppress growth of larger aggregates. SiC is easier to synthesize since the precursor polymers are not hydrolysis sensitive and higher specific surfaces can be generated. Unfortunately, the N-atoms which stabilize very small and highly reactive metal nanoclusters or particles are not present. A combination of the advantages would be porous N-doped SiC. Preliminary works support this hypothesis. Regarding 2.: In this subproject, we are interested in: a) the cobalt catalyzed reductive amination for the synthesis of primary amines under mild conditions, b) the hydrogenation of nitriles in the presence of functional groups easily to hydrogenate, and c) the design of selective (de)hydrogenation catalysts of so far rarely or never used 3d metals.