Thermally functional and reversible thermal conductivity switching in nanoporous molecular frameworks

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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.