NSF-BSF: CAS: Green Hydrogen from Liquid-Organic Hydrogen Carriers Using Supported Molecular Catalysts

为了应对气候变化，需要全球努力减少二氧化碳（CO2）排放。为此，可持续的氢气生产——作为一种能源和许多化学品的关键组成部分——将在取代化石资源及其相关的二氧化碳排放方面发挥关键作用。由于氢的气体性质，氢的运输和储存都具有挑战性。该项目通过研究液态有机氢载体（lohc）的有效设计和利用来解决这些挑战，lohc是一种富含氢的化学品，以商品规模生产，并以液体形式运输/储存。lohc的设计还必须使它们能够根据需要随时释放氢，并能有效地回收到富氢状态。该项目通过与以色列魏茨曼科学研究所的研究人员的国际合作，重点研究催化剂技术，使几个有前途的LOHC系统能够实现更困难的反应，包括氢释放。lohc代表了一种可行的大规模可再生能源存储方法，它有可能消除基于电池、液氢和液氨的竞争技术的固有局限性。该项目在可溶性和固体催化方法的界面上进行操作，以推进负载分子催化剂（SMCs）的设计、合成、表征和性能。目标lohc建立在Milstein集团在乙二醇（EG）脱氢聚合形成聚酯和氢气以及反加氢再生EG方面的开创性发展之上；他们还利用了以色列小组最近设计的有前途的催化剂，这些催化剂以甲酸（FA）作为氢载体。该项目将该团队的进展与美国团队的固体催化剂设计和合成方法相结合，在一定程度上保留了有机配体对均相系统催化作用的控制，同时提供了固体催化剂的优势，包括催化剂易于回收、稳定性和活性增强。实现这些目标需要将可溶性催化剂中有机配体赋予的可调性与固体催化剂实现的氢储存和释放的解耦结合起来。该合作依赖于两种新兴的在固体催化剂表面支持分子位点的策略：(i)静电锚定在沸石外表面口袋上；（ii）在多孔非晶载体上机械封装活性位点。这些方法可以控制催化剂所经历的外部环境，而通过锚定定义明确的金属配合物来实现对活性位点的内部控制。该项目将在几个领域推进最先进的技术，包括SMCs的合成、x射线吸收光谱表征和分子建模。除了技术方面，NSF项目还将为研究生和本科生提供指导机会，重点关注STEM中代表性不足的群体。Katz实验室的成员将在BASIS和BEAM项目中组成团队；这些团队将自愿在东湾经济落后地区的当地中小学教授科学课程。此外，该项目将通过加州NERDS项目UC LEADS和NSF CAMP为STEM中代表性不足的群体的本科生提供研究机会，这些项目旨在增加STEM中的多样性，并强调非洲裔美国人、拉丁裔美国人和印第安人学生的参与。此外，这项研究的结果将通过整合到催化剂设计选修课程中传播给广泛的受众。该项目由CBET部门催化项目和化学部门化学催化项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In order to address climate change, global efforts to reduce carbon dioxide (CO2) emissions are needed. To that end, sustainable production of hydrogen – as both an energy source and critical component of many chemicals – will play a key role in displacing fossil resources and their associated CO2 emissions. Because of its gaseous nature, both the transport and storage of hydrogen are challenging. The project addresses those challenges through research focused on the efficient design and utilization of Liquid Organic Hydrogen Carriers (LOHCs) – chemicals that are rich in hydrogen, manufactured at commodity scale, and transported/stored in liquid form. LOHCs must also be designed such that they readily release the hydrogen as needed and can be efficiently recycled to their hydrogen-rich state. The project focuses on catalyst technology enabling the more difficult reaction involving hydrogen release, for several promising LOHC systems, through an international collaboration with researchers at the Weizmann Institute of Science in Israel. LOHCs represent a viable approach for large-scale renewable energy storage that has the potential to obviate the inherent limitations of competing technologies based on batteries, liquid hydrogen, and liquid ammonia. The project operates at the interface of soluble- and solid-catalysis methodologies to advance the design, synthesis, characterization, and performance of supported molecular catalysts (SMCs). The targeted LOHCs build on pioneering developments in the Milstein group for dehydrogenative polymerization of ethylene glycol (EG) to form polyesters and hydrogen, and the reverse hydrogenation to regenerate EG; they also leverage promising recent catalysts designed by the Israeli group that function with formic acid (FA) as a hydrogen carrier. The project combines that group's progress with the U.S. team's solid-catalyst design and synthesis approaches, which enable a degree of preservation of organic-ligand control over catalysis typically associated with homogeneous systems, while offering advantages of solid catalysts that include ease of catalyst recovery and enhanced stability and activity. Achieving those goals involves fusing the tunability imparted by organic ligands in soluble catalysts to the decoupling of hydrogen storage and release enabled by solid catalysts. The collaboration relies on two emerging strategies for supporting molecular sites on a solid catalyst surface: (i) electrostatic anchoring on zeolite external-surface pockets and (ii) mechanical encapsulation of active sites on porous amorphous supports. These approaches enable control over the outer-sphere environment experienced by the catalyst, while inner-sphere control of the active site is achieved by anchoring well-defined metal complexes. The project will advance the state-of-the-art in several areas, including synthesis of SMCs, characterization via X-ray absorption spectroscopy, and molecular modeling. Beyond the technical aspects, the NSF project will provide mentorship opportunities for graduate and undergraduate students, with an emphasis on underrepresented groups in STEM. Members of the Katz lab will form teams in the programs BASIS and BEAM; these teams will volunteer to teach science lessons in local elementary and middle schools in economically-disadvantaged areas in the East Bay. In addition, the project will provide research opportunities for undergraduate students in underrepresented groups in STEM through the Cal NERDS programs UC LEADS and NSF CAMP, which seek to increase diversity within STEM, and stress participation from African American, LatinX, and Native American students. Furthermore, results from this research will be disseminated to a broad audience via integration into an elective course on catalyst design. The project is co-funded by the CBET Division Catalysis program and the Chemistry Division Chemical Catalysis program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.