Epitaxially Grown Metal-Organic Frameworks: Design, Preparation, and Application as Multi-Component Films in Tandem Catalysis

正如自然界中许多催化酶组件所示，位点分离是进行串联催化反应以合成高度复杂分子的有力策略。该项目的目标是基于分子外延方法制备衬底支持的高取向mof，然后在串联催化中研究这种新型的逐层生长的mof。该方法也将解决催化剂的不相容性问题。此外，即使在不存在不相容性的情况下，多相化催化剂也会大大提高其稳定性。由于MOF具有稳定和结晶的可调结构，我们认为通过精心设计在单个MOF中集成多种功能是可行的。在本提案中，为了实现高原子效率和能源效率的可持续有机合成，还强调了使用多功能催化剂开发无中间分离步骤的一锅级联工艺。在这个项目中，我们建议制备一类新的mof，为部署两种不同的均相催化剂提供一个令人兴奋的平台，作为下一代选择性和稳定的非均相催化剂体系的基石。重要的是，这些材料中的催化活性部分可以以位点隔离的方式制造，并且围绕它们的空腔可以被设计成概念上模仿酶。该项目阐述了四种不同类型的新型催化剂，包括：i)金属卟啉/萨伦催化烯烃环氧化，然后捕获二氧化碳形成环状碳酸盐；ii)金属卟啉通过原位生成的亚硝基催化C-H胺化，然后利用碳当量插入N-H；iii)金属卟啉催化类碳化合物插入S-H键，随后光诱导硫化物亚砜化；iv) Grubbs第二代催化剂与不相容催化剂（ir -钳子）的位点分离，从而导致烷烃复分解。

As exemplified by many catalytic enzyme assemblies in nature, site-isolation is a powerful strategy for performing tandem catalytic reactions to synthesize highly complex molecules.The goals of the project would be to prepare substrate supported, highly oriented MOFs based on the molecular epitaxial approach and then the study of such novel layer-by-layer grown MOFs in tandem catalysis. This approach also would bring a solution to catalysts incompatibility problem. In addition, heterogenizing the catalysts should greatly enhance their stability, even in the absence of an incompatibility. Because MOFs possess tunable structures which are stable and crystalline, we perceived it feasible to integrate multiple functions within one single MOF through a careful design. In this proposal, to achieve sustainable organic synthesis with a high atom and energy efficiency, the development of one-pot cascade processes with no intermediate separation steps using multifunctional catalysts is also highlighted.In this project, we propose to prepare a new class of MOFs providing an exciting platform for deploying two different homogeneous catalysts as building blocks for the next generation of selective and stable heterogeneous catalyst systems. Importantly, the catalytically active moieties in these materials can be made in a site-isolated fashion and the cavities that surround them can be engineered to conceptually to mimic enzymes.Four different classes of novel catalyses are illustrated in the project including: i) metallo- porphyrins/salens catalyzed olefin epoxidation followed by CO2 capture to form cyclic carbonates; ii) metalloporphyrins catalyzed C-H amination via in situ generated nitrenes followed by N-H insertion utilizing carbene equivalents; iii) metalloporphyrins catalyzed insertion of carbenoids into S-H bond followed by photo-induced sulfoxidation of the resulting sulfides and iv) site-isolation of Grubbs second-generation catalysts from the incompatible catalysts (Ir-pincer) which would lead to alkane metathesis.