Tunability of Thermal Conductivity in Porous 2D-Covalent Organic Frameworks

Covalent organic frameworks (COFs) are a unique class of porous material, in which chemists can easily modulate multiple properties of the COFs by varying the nodes and linkers that make up the framework. The interchangeability of these organic building blocks allows for the structures to have a multitude of applications such as gas separation, catalysis, sensing, electronic devices, energy storage, and more. Conversely, the ability to implement COFs in these applications was limited due to the COFs polycrystalline powder form. In recent years, there has been a large effort to grow 2D COF thin films, which resulted in films with thermal conductivities of 1.0 W m^-1 K^-1. In this presentation, we will use both time-domain thermoreflectance (TDTR) and steady state thermoreflectance (SSTR) to measure thermal and mechanical properties of a variety of COF thin films, including boronate-ester and imine-linked 2D COFs. TDTR and SSTR are non-contact, laser-based, pump-probe measurement techniques, which relate the change in reflectivity of the sample surface, to the thermal conductivities of the COF films below. We will discuss the effects of film thickness, connectivity, and pore functionality on the thermal properties of COF thin films.