RUI: New Ultrastable Crystalline Porous Materials

非技术SUMMARY金属-有机骨架是由配位于有机配体的金属中心组成的分子规模的筛子，其结果是具有均匀孔径的三维结构。它们可以实现或改善大规模的能源、健康和国防应用，如气体储存和分离、水和其他化学去污、直接从空气中收集水和二氧化碳以及核废物处理。然而，目前很少有金属-有机骨架材料具有合适的孔隙率和化学稳定性的组合来满足这些应用的要求。开发化学稳定性和孔径可调的金属-有机骨架是最重要的科学挑战之一，也是该项目的目标，该项目得到了材料研究部固体和材料化学计划的支持。该项目旨在通过同时创建高度连接的结构积木和刚性框架来实现高化学稳定性，这些结构块和刚性框架不容易被常见的分子和分子碎片(如水和氢氧化物离子)分解。这些新材料的孔几何形状可以使用不同的组合、结构构建块和有机配体来调整。通过开发这些新的合成途径，创造了在金属-有机骨架材料中具有最高化学稳定性的新材料，这些材料可以在现实应用中常见的苛刻化学条件下使用。此外，该项目还支持各种研究活动，并为加州州立大学长滩的不同本科生和研究生提供了丰富的培训机会。技术总结在材料研究部固态和材料化学计划的支持下，卜先辉教授和他的研究小组开发了合成途径，以创造一系列新的超稳定和超可用金属-有机骨架材料。该结构平台在金属-配位键类型(例如，金属-羧酸盐、金属-氮酸盐、金属-吡啶)中具有非凡的灵活性，允许在相同的等结构系列材料中对孔隙率、功能性和稳定性进行高水平的控制。为了扩大金属-有机骨架酸碱稳定性的界限，研究人员合成了具有高连接性(高于6)的三聚体构建块的基于铬的三聚体骨架。在本项目之前，只有低连接的铬金属有机骨架(6个或更少)是已知的，在这个项目中，通过混合铬-氧和铬-氮交联剂创建高连接的骨架材料，进一步增加了三价金属离子的动力学惰性，并通过配位物种保护金属节点免受化学攻击。研究人员还系统地探索了关键的实验参数，如反应温度、溶剂类型和调节剂，与大多数金属-有机框架中的不稳定离子相比，所有这些参数在本项目中对非活性金属离子的作用都要大得多。该项目将实现的综合组成和结构特征同时提高了低pH和高pH方向的酸碱稳定性。这些材料具有特殊的化学稳定性，可实现广泛的应用，特别是那些在苛刻的化学条件下运行的应用，如核废物处理。此外，该项目支持各种研究活动，并为加州州立大学长滩分校的不同本科生和研究生提供丰富的培训机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYMetal-organic frameworks are molecular-scale sieves composed of metal centers coordinated to organic ligands, which results in three-dimensional structures with uniform pore size. They can enable or improve large-scale energy, health, and defense applications such as gas storage and separation, water and other chemical decontamination, direct water harvesting and carbon dioxide capture from air, and nuclear waste treatment. However, currently few metal-organic framework materials have a suitable combination of porosity and chemical stability to meet the demands of these applications. Developing chemically stable and pore-size-tunable metal-organic frameworks is among the most important scientific challenges and is the objective of this project, which is supported by the Solid State and Materials Chemistry program in the Division of Materials Research. The project aims to impart high chemical stability by simultaneously creating highly connected structural building blocks and rigid frameworks that are not easily broken down by common molecules and molecular fragments, such as water and hydroxide ions. The pore geometry of these new materials can be tuned using different combinations structural building blocks and organic ligands. By developing these new synthesis pathways new materials with the highest chemical stability among metal-organic framework materials are created that can be used under harsh chemical conditions commonly encountered in real-world applications. In addition, this project enables a variety of research activities and provides rich training opportunities for a diverse population of undergraduate and graduate students at California State University – Long Beach.TECHNICAL SUMMARYWith this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Prof. Xianhui Bu and his research group develop synthetic pathways to create a family of new ultrastable and ultratunable metal-organic framework materials. The structural platform has an extraordinary flexibility in metal-ligand bond type (e.g., metal-carboxylate, metal-azolate, metal-pyridyl), which allows a high level of control over porosity, functionality, and stability within the same isoreticular series of materials. To expand the boundaries in acid-base stability of metal-organic frameworks, the researchers synthesize chromium-trimer-based frameworks with the high-connected (higher than 6) trimer building block. Only low-connected chromium metal-organic frameworks (6 or less) were known prior to this project, and the creation of high-connected framework materials in this project with mixed Cr-O and Cr-N crosslinks further increases the kinetic inertness of trivalent metal ions and also shields the metal nodes from chemical attacks by coordinating species. The researchers also systematically explore key experimental parameters such as reaction temperature, solvent type, and modulators, all of which play a far greater role for nonlabile metal ions in this project, compared to labile ions in most metal-organic frameworks. The integrated compositional and structural features to be achieved in this project increase acid-base stability simultaneously in both low- and high-pH directions. The exceptional chemical stability of these materials can enable a broad range of applications, especially those that operate under harsh chemical conditions such as nuclear waste treatment. In addition, this project enables a variety of research activities and provides rich training opportunities for a diverse population of undergraduate and graduate students at California State University – Long Beach.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.