Thermally functional and reversible thermal conductivity switching in nanoporous molecular frameworks

美国的能源消耗主要依赖于煤炭和石油等不可再生资源，这些资源会导致大量有毒排放。此外，大部分能源消耗都被浪费为热量。这种有毒环境排放和高能源低效的组合要求更好的热工程策略，能够有效地将废热作为可重复使用的能源来利用，从而降低在此过程中不断消耗的不可再生资源的消耗。一种创新的策略是通过热开关主动控制电子设备中的热流，这一策略超越了利用被动热元件来冷却电子设备的传统方法。该项目将以2D聚合物的最新进展为基础，设计具有优异热开关性能的新材料。通过这个项目，将启动与当地高中的合作，为K-12教师和学生开发教育模块，为他们提供机会，通过普罗维登斯学校系统的课外活动接触纳米技术，普罗维登斯学校系统是罗德岛最大的城区。这项拟议研究计划的总体目标是开发一种基于分子框架材料的动态热开关的自下而上设计标准，具有主动操纵热梯度的能力，具有高开关率和快速响应时间。该项目团队将通过实施理论和实验方法，对2D共价有机骨架的结构-性质关系进行系统研究，2D共价有机骨架是一种新兴的结晶和多孔聚合物材料。所有的测量都将利用泵浦-探测光谱学技术的进步来进行，这些实验将得到第一性原理计算和分子动力学模拟的证实，以访问涉及这些新材料中不同类型的能量载流子的原子和模能级动力学过程。该项目将促进对分子骨架材料、2D多孔薄膜和杂化界面中在结构相变和外部刺激引起的电子结构变化下发生的能量传输机制的基本理解。这将为实现由2D聚合物中具有高表面积的一维孔道促进的热、质量和电荷传输属性的新范例打开大门。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。

The energy consumption of the United States primarily relies on nonrenewable resources such as coal and petroleum that lead to large quantities of toxic emissions. Also, most of the energy consumption is wasted as heat. This combination of toxic environmental emissions and high energy inefficiencies demands better thermal engineering strategies capable of efficiently utilizing the wasted heat as reusable energy, thus lowering the consumption of the ever-depleting nonrenewable resources in the process. One innovative strategy, which goes beyond the traditional approach of utilizing passive thermal components to cool electronic devices is to actively control heat flow in electronics through thermal switches. This project will build on recent advances in 2D polymers to design new materials with superior thermal switching properties. Through this project, collaboration with local high schools will be initiated to develop educational modules for K-12 teachers and students providing opportunities for them to get exposure to nanotechnology through extracurricular activities in the Providence school system, which is the largest urban district in Rhode Island.The overarching goal of this proposed research program is to develop a bottom-up design criterion for a dynamic thermal switch based on molecular framework materials, possessing the ability to actively manipulate thermal gradients with high switching ratios and fast response times. The project team will perform systematic studies of structure-property relationship on 2D covalent organic frameworks, an emerging class of crystalline and porous polymeric materials, by implementing both theoretical and experimental approaches. All measurements will be performed using advancements in pump-probe optical spectroscopy techniques and these experiments will be corroborated with first-principles calculations and molecular dynamics simulations to access the atomistic and mode-level dynamical processes involving different types of energy carriers in these novel materials. This project will advance the fundamental understanding of energy transport mechanisms in molecular framework materials, 2D porous thin films and across hybrid interfaces occurring under structural phase transitions and electronic structure changes resulting from externally applied stimuli. This will open doors for the realization of new paradigms in heat, mass and charge transport properties that are facilitated by the 1D pore channels with high surface areas in 2D polymers.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.