Hybrid Organic-Inorganic Active Sites for Selective Heterogeneous Catalysis

用于选择性多相催化的杂化有机-无机活性位点

• 批准号: 0854560
• 负责人: Alexander Katz
• 金额: $ 23.49万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0854560&HistoricalAwards=false
• 关键词: Hybrid; Organic; Inorganic; Active; Sites

0854560 KatzEmerging applications of heterogeneous catalysis require the development of new materials that i) afford high catalyst selectivity and activity at the relatively low temperatures required to avoid background degradation reactions of critical chemical intermediates, and ii) function without leaching/degradation in aqueous and harsh organic solvent environments. This work addresses the pressing needs in (i) and (ii) above via the design and synthesis of heterogeneous catalysts consisting of multifunctional organic active sites. The organic component of these active sites inherently lends them to being hydrolytically stable while simultaneously providing tailorability of molecular structure for control of function. The intellectual merit of this research is to implement emerging concepts in the synthesis of organic acid and base active sites as relevant precursors for highly selective, active, and robust heterogeneous catalysts, which consist of a hybrid organic-inorganic material. The work specifically exploits the confinement of catalytic sites on the surface of silica and control reactivity of the resulting confined functional groups using calixarenes as an organizational scaffold and confinement entity.Upon calixarene grafting, lateral metathesis polymerization of anchored calixarenes on the inorganic-oxide surface synthesizes a robust two-dimensional crosslinked polymer consisting of immobilized catalytically active sites. This polymer is insoluble and is therefore expected to be leach-proof even under severe solvent environments, such as those involving high temperatures and aqueous solvent systems. Preliminary experiments aimed at demonstrating proof of concept are geared towards demonstrating robust and highly selective aldol condensation activity, a reaction that is key to fine chemicals and biorefining, in a variety of solvent environments using a recoverable catalyst, as well as the synthesis of enantioselective acid-base bifunctional catalysts based on this concept.These goals require the development of confined calixarene active sites containing acidic functionality, as well as sites containing base, which are attainable using procedures recently developed by our research group. Acid active sites will be investigated for reactions relevant to biorefining such as transesterification and ester hydrolysis. We further develop approaches to pattern the surface of an inorganic oxide, using silica as a model inorganic-oxide, with two disparate chemical functional groups, because methods of site isolation discovered during this process are likely to be generally applicable to other catalytic systems of relevance to other transformations, such as those involving supported metal and inorganic-oxide nanoparticles. The research activities broadly impact the training of future scientists in catalyst design and synthesis, with specific emphasis on structural characterization and functional assessment of hybrid organic-inorganic catalysts with designed nanoscale structure and connectivity. The training of graduate and undergraduate students will have special emphasis placed on the recruitment of female and minority students. Outreach activities include a K-12 component, with a focus on encouraging Pacific Islander minorities to pursue study of the chemical sciences and engineering, through inspirational research presentations to high-school students on the topic of future directions and challenges in and research while simultaneously providing a demonstration of how scientific discoveries can be used for creating new technology and understanding.

0854560 Katz多相催化的新兴应用需要开发新的材料，i)在相对较低的温度下提供高的催化剂选择性和活性，以避免关键化学中间体的背景降解反应，以及ii)在水和严酷的有机溶剂环境中不发生淋溶/降解。这项工作通过设计和合成由多功能有机活性中心组成的多相催化剂来满足上述(I)和(Ii)中的迫切需求。这些活性中心的有机成分固有地使它们具有水解性稳定性，同时提供了用于控制功能的分子结构的可调性。这项研究的智力价值在于将合成有机酸和碱活性中心的新概念作为高选择性、活性和坚固的多相催化剂的相关前体，这些多相催化剂由有机-无机混合材料组成。这项工作特别利用了二氧化硅表面催化中心的限制，并使用杯芳烃作为组织支架和限制实体来控制得到的受限官能团的反应活性。在杯芳烃接枝的基础上，固定在无机氧化物表面的杯芳烃的侧向歧化聚合合成了一种由固定催化活性中心组成的坚固的二维交联型聚合物。这种聚合物是不溶的，因此即使在恶劣的溶剂环境中，例如涉及高温和水溶剂系统的环境中，也有望保持防浸出。初步实验旨在演示概念验证，旨在展示在各种溶剂环境中使用可回收催化剂的强大和高选择性的羟醛缩合活性，这是精细化工和生物精制的关键反应，以及基于这一概念合成对映体选择性酸碱双功能催化剂。这些目标需要开发包含酸性官能团的受限杯芳烃活性中心以及包含碱的活性中心，这些都可以使用我们研究小组最近开发的程序实现。将研究与生物精制相关的反应的酸性活性部位，如酯交换和酯水解。我们进一步开发了利用二氧化硅作为模型无机氧化物，具有两个不同的化学官能团的无机氧化物表面图案的方法，因为在此过程中发现的位置隔离方法很可能普遍适用于与其他转化相关的其他催化体系，如涉及负载型金属和无机氧化物纳米颗粒的催化体系。这些研究活动广泛影响未来科学家在催化剂设计和合成方面的培训，特别强调具有设计的纳米级结构和连接性的有机-无机杂化催化剂的结构表征和功能评估。研究生和本科生的培养将特别重视招收女性和少数民族学生。外联活动包括K-12部分，重点是鼓励太平洋岛民少数群体继续学习化学科学和工程学，向高中生提供鼓舞人心的研究报告，主题是未来的方向和研究方面的挑战，同时展示如何利用科学发现创造新技术和增进理解。