Thermally functional and reversible thermal conductivity switching in nanoporous molecular frameworks

美国的能源消费主要依赖煤炭和石油等不可再生资源，导致大量有毒气体排放。此外，大部分的能源消耗被浪费为热量。这种有毒环境排放和高能源效率的结合需要更好的热工程策略，能够有效地利用废热作为可重复使用的能源，从而降低过程中不断消耗的不可再生资源的消耗。一种创新策略超越了利用无源热元件冷却电子设备的传统方法，即通过热开关主动控制电子设备中的热流。该项目将基于2D聚合物的最新进展，设计具有上级热开关性能的新材料。通过该项目，将开始与当地高中合作，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，这是罗得岛最大的城市区。这项拟议的研究计划的总体目标是开发一个底部-提出了一种基于分子骨架材料的动态热开关的设计标准，具有主动操纵热梯度的能力，具有高的开关比和快速的响应时间。该项目团队将通过实施理论和实验方法，对2D共价有机框架（一种新兴的结晶和多孔聚合物材料）的结构-性能关系进行系统研究。所有测量将使用先进的泵浦探测光谱技术进行，这些实验将与第一原理计算和分子动力学模拟相证实，以获得涉及这些新型材料中不同类型能量载体的原子和模式级动力学过程。该项目将推进对分子框架材料，2D多孔薄膜和混合界面中能量传输机制的基本理解，这些机制发生在结构相变和外部施加刺激导致的电子结构变化下。这将为实现热、质量和电荷传输特性的新范例打开大门，这些特性是由二维聚合物中具有高表面积的一维孔通道促进的。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.