CAS:Mechanochemical Activation Carriers and Mechanisms by in Situ Chemical Kinetics Monitoring

CAS：原位化学动力学监测机械化学活化载体和机制

• 批准号: 2154893
• 负责人: Silvina Pagola
• 金额: $ 39.9万
• 依托单位: Old Dominion University Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2154893&HistoricalAwards=false
• 关键词: CAS; Mechanochemical; Activation; Carriers; Mechanisms

With support from the Chemical Structure, Dynamics, and Mechanisms-B (CSDM-B) Program of the Chemistry (CHE) Division, and the Solid State and Materials Chemistry (SSMC) Program of the Division of Materials Research (DMR), Dr. Silvina Pagola at Old Dominion University will investigate fundamental aspects of mechanochemical reactions and their mechanisms. Mechanochemistry is the field of chemistry studying reactions induced by mechanical forces and the Incorporation of mechanical energy. Mechanochemical reactions largely reduce or avoid the use of reaction solvents. They are "green" chemical processes, increasingly used toward the preparation of inorganic, organic and metal-organic materials. However, the chemical mechanisms of mechanochemical reactions remain poorly understood, which limits their implementation. This project will test a theoretical model hypothetically embodying critical differences between the energetics of mechanochemical reactions and their counterparts driven only by thermal activation. Methods to determine the activation barriers of mechanochemical reactions will be developed. These studies have the potential to open up a new perspective on mechanochemistry, and new ways of quantitatively modeling mechanochemical activation. Such an approach has the potential to serve as a valuable tool for others seeking to develop mechanochemical approaches as more sustainable alternatives to existing chemical processes, with attendant environmental and economic benefits. Educational activities associated with this project include the training of graduate and undergraduate students, along with the inclusion of individuals underrepresented in STEM (science, technology, engineering and mathematics) fields. Yearly workshops on solving crystal structures from X-ray powder diffraction using freely distributed software will be also organized. This research seeks to develop methods to measure and interpret the meaning of the activation barriers of mechanochemical reactions. Knowledge from homogeneous-phase kinetics and chemical mechanisms will be combined with the use of recently developed in situ kinetics monitoring techniques and instrumentation to measure the activation barriers of mechanochemical reactions. The validity and scope of a “stress-augmented thermal activation” theoretical model will be investigated. This model implies a reduction in the Gibbs free energy of activation of mechanochemical reactions in comparison with reactions driven only by thermal activation, by incorporating a phenomenological work term resulting of an external force applied to the reactants along the reaction coordinate. This effect is coupled with the excitation of vibrational modes by the mechanical treatment, synergistically reducing the mechanochemical activation barriers. Three types of mechanochemical reactions will be investigated: (1) The mechanosynthesis of ZIF-6, a metal-organic framework; (2) two Diels-Alder cycloadditions (covalent mechanochemistry); (3) the mechanochemical organic co-crystallization of tetrathiafulvalene and chloranilic acid, and the chemical mechanisms leading to ionic and neutral polymorphs. Isothermal kinetic data will be measured in situ from a ball mill using Raman spectroscopy, supported by ex situ X-ray powder diffraction. The activation barriers will be calculated from Arrhenius and Eyring graphs. The variation of the Gibbs free energy of activation values will be analyzed for several combinations of milling parameters, leading to a systematic increase of the overall mechanical energy inputs.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.

在化学（CHE）部门的化学结构，动力学和机制-B（CSDM-B）计划以及材料研究部门（DMR）的固态和材料化学（SSMC）计划的支持下，Old自治领大学的Sildenafi Pagola博士将研究机械化学反应及其机制的基本方面。机械力化学是研究由机械力引起的反应和机械能的结合的化学领域。 机械化学反应大大减少或避免了反应溶剂的使用。它们是"绿色"化学过程，越来越多地用于制备无机、有机和金属有机材料。然而，机械化学反应的化学机制仍然知之甚少，这限制了它们的实施。本项目将测试一个理论模型，该模型假设体现了机械化学反应的能量学与仅由热活化驱动的对应物之间的关键差异。将开发确定机械化学反应活化势垒的方法。这些研究有可能开辟一个新的视角机械化学，和新的方法定量建模机械化学活化。 这种方法有可能成为其他人寻求开发机械化学方法作为现有化学工艺的更可持续替代品的宝贵工具，并带来环境和经济效益。与该项目相关的教育活动包括培训研究生和本科生，沿着纳入在STEM（科学、技术、工程和数学）领域代表性不足的个人。还将组织关于利用免费分发的软件从X射线粉末衍射解算晶体结构的年度讲习班。 本研究旨在开发方法来测量和解释机械化学反应的活化势垒的含义。将结合使用最近开发的原位动力学监测技术和仪器来测量机械化学反应的活化屏障，从非平衡相动力学和化学机制的知识。将研究"应力增强热活化"理论模型的有效性和适用范围。该模型意味着减少吉布斯自由能的机械化学反应的活化相比，仅由热活化驱动的反应，通过将一个现象学的工作长期导致的外力施加到反应物沿着反应坐标。这种效应与通过机械处理激发振动模式相结合，协同降低了机械化学活化屏障。将研究三种类型的机械化学反应：（1）ZIF-6，金属有机骨架的机械合成;（2）两个Diels-Alder环加成（共价机械化学）;（3）四硫富瓦烯和氯冉酸的机械化学有机共结晶，以及导致离子和中性多晶型物的化学机制。等温动力学数据将使用拉曼光谱法从球磨机中原位测量，并得到非原位X射线粉末衍射的支持。激活势垒将根据Arcidius和Eyring图计算。活化值的吉布斯自由能的变化将被分析为铣削参数的几种组合，导致整体机械能输入的系统性增加。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。