Directly measured high in-plane thermal conductivity of two-dimensional covalent organic frameworks
Jinghang Dai, Qiyi Fang, Gustavo A. Alvarez, Amelia F. Schaeffer, Kirt A. Page, Jiyoung Kim, Samuel M. Kielar, Joyce Christiansen‐Salameh, Eugene Jeong, Dayanni D. Bhagwandin, Jinha Kwon, Ly D. Tran, Md. Sherajul Islam, Ajit K. Roy, Nicholas R. Glavin, Yu Zhong, Jun Lou, Zhiting Tian
Abstract
Two-dimensional covalent organic frameworks are promising low-density porous materials for lightweight thermal management, yet comprehensive thermal conductivity measurements remain scarce. Particularly, direct in-plane thermal conductivity data for large-area, fully suspended covalent organic framework thin films has not been reported previously. This study addresses this gap by measuring in-plane and cross-plane thermal conductivities of two-dimensional covalent organic frameworks with varying pore sizes using laser-based pump-probe techniques. Transient thermal grating spectroscopy revealed a high in-plane thermal conductivity of 1.18 ± 0.21 W/(m⋅K) for a sample with a 1.4 nm pore size, highlighting a notable pore size effect. Cross-plane thermal conductivity measured via frequency-domain thermoreflectance indicated weak thermal anisotropy for samples with larger pores. Grazing-incident wide-angle X-ray scattering provided structural insights and clarified heat conduction mechanisms. These direct in-plane thermal conductivity measurements enhance understanding of thermal transport behaviors in covalent organic frameworks, supporting their development as advanced thermal management materials. The few options available for the measurement of in-plane and cross-plane thermal conductivity of covalent organic frameworks films limit their application for lightweight thermal management. Here, the authors measure both, the in-plane and cross-plane thermal conductivity of two dimensional covalent organic frameworks with different pore sizes using laser-based pump-probe techniques.