CAREER: Transition Metal Chalcogenide Clusters: Preformed Building Blocks for Framework Materials

块状过渡金属硫化物(TMC)是重要的储能材料、电子器件和催化材料。然而，TMC通常是在高温高压下合成的，或者使用剥离技术分离出来的。传统的TMC材料合成方法缺乏精确的结构控制，从而限制了它们针对特定应用进行合理调整的能力。在材料研究部固态和材料化学项目的支持下，Christopher Bejger教授研究了如何将纳米尺寸的TMC碎片用作具有高比表面积的多维支架的构建块，即所谓的金属-有机骨架(MOF)。MOF具有坚固的稳定性和晶体结构，并且可以预测地合成。由此产生的混合材料具有传统的、块状TMCs和晶态MOF的特征。由TMC单元制成的框架经历了多次可逆的氧化状态变化。因此，TMC-MOF对纳米电子学和未来电荷存储器件的研究具有重要意义。这些材料的设计为综合教育部分提供了灵感。在分子和材料设计原理的影响下，PI与北卡罗来纳大学夏洛特建筑学院的Rachel Dickey教授合作，计划并建造了一个互动的纳米级科学弹出博物馆。Pi和他的建筑同事还与夏洛特师范学院(CTI)合作，为夏洛特-梅克伦堡学校(CMS)的教师举办了一系列研讨会，题为“设计物质(S)”，并主持了一次教师暑期研究体验。技术总结这项研究项目，在材料研究部固态和材料化学计划的支持下，研究了一类新的氧化还原活性金属-有机骨架(MOF)，由过渡金属硫化物(TMC)分子簇组成。TMC团簇表现出丰富的电化学行为，并倾向于经历可逆的多电子转移事件。然而，由于缺乏合适的合成方案，它们在MOF化学中的应用受到限制。Bejger研究小组使用具有辅助官能团的膦配体将预先形成的原子定义的金属硫化物单元合并到多维框架中。探索了几种策略来扩展通式MxSy(M=Ni，Co，Mo，Fe)的前体的化学计量和结构组合。材料的组成、拓扑和表面积被量身定做，以控制氧化还原活性簇的排列和电荷。TMC团簇具有混合价、离域的金属硫族核心，这些核心提供了跨越氧化态的结构完整性，并充当电子储存库。对经过稳定充放电循环的TMC-MOF进行了储能应用研究。研究了用于锂离子电池的TMC-MOF双功能充电正极。这项提案的教育部分旨在通过建筑和设计的视角增加公民对材料化学的参与。弹出式博物馆是与北卡罗来纳大学夏洛特建筑学院合作设计和制造的项目。教育计划是多方面的，强调了MOF拓扑、网状综合和建筑之间的联系。博物馆概念中提出的想法通过与夏洛特师范学院(CTI)的合作传播并发展为当地教师的课程。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 SUMMARYBulk transition metal chalcogenides (TMCs), are important materials for energy storage, electronic devices, and catalysis. However, TMCs are typically synthesized at high temperatures and pressures or are isolated using exfoliation techniques. Traditional synthetic approaches to TMC materials lack precise structural control, thus limiting their ability to be rationally tuned for specific applications. With this CAREER project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Prof. Christopher Bejger studies how nano-sized fragments of TMCs can be used as building blocks for multidimensional scaffolds with high surface areas, known as metal-organic frameworks (MOFs). MOFs offer robust stability, crystalline structures, and can be predictably synthesized. The resulting hybrid materials share features of both conventional, bulk TMCs and crystalline MOFs. Frameworks made from TMC units undergo multiple, reversible oxidation state changes. Thus, TMC-MOFs are relevant to the study of nanoelectronics and future charge storage devices. The design of these materials provides inspiration for an integrated education component. The PI plans and fabricates an interactive Nanoscale Science Pop Up Museum, influenced by the principles of molecular and materials design, in collaboration with Prof. Rachel Dickey at the UNC Charlotte School of Architecture. The PI and his architecture colleague also partner with the Charlotte Teachers Institute (CTI) to present a seminar series for Charlotte-Mecklenburg School (CMS) teachers titled "Design Matter(s)" and host both science and art educators in a Summer Research Experience for Teachers.TECHNICAL SUMMARYThis research project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, investigates a new class of redox-active metal-organic frameworks (MOFs) comprising transition metal chalcogenide (TMC) molecular clusters. TMC clusters exhibit rich electrochemical behavior and have a propensity to undergo reversible, multi-electron transfer events. However, their use in MOF chemistry is limited by a lack of suitable synthetic protocols. The Bejger research group uses phosphine ligands with ancillary functional groups to incorporate pre-formed, atomically defined, metal-sulfide units into multidimensional frameworks. Several strategies are explored to expand the stoichiometric and structural combinations of precursors of the general formula MxSy (M= Ni, Co, Mo, Fe). The composition, topology, and surface areas of the materials are tailored to control the arrangement and charge of redox-active clusters. TMC clusters have mixed-valence, delocalized, metal-chalcogen cores that provide structural integrity across oxidation states and serve as electron reservoirs. Select TMC-MOFs that undergo stable charge/discharge cycling are studied for energy storage applications. TMC-MOF cathodes that mediate bifunctional charging are investigated for use in lithium ion batteries. The educational component of this proposal aims to increase civic engagement with materials chemistry through the lens of architecture and design. A pop-up museum is designed and fabricated as a collaborative project with the UNC Charlotte School of Architecture. The educational plan is multifaceted to emphasize links between MOF topology, reticular synthesis, and architecture. The ideas presented in the museum concept are disseminated and developed into a curriculum for local teachers through a partnership with the Charlotte Teachers Institute (CTI).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.