Supramolecular Interactions lead to Remarkably High Thermal Conductivities in Interpenetrated Two Dimensional Porous Crystals

The design of innovative porous crystals with high porosities and large surface areas has garnered a great deal of attention over the past few decades due to their potential for a variety of applications, including flexible electronics, gas storage, and catalysts, among others. However, heat dissipation poses a major challenge in porous crystals and enhancing heat dissipation is key to realizing their potential. In this work, we use systematic atomistic simulations to show that the interpenetration of two, two-dimensional frameworks possess remarkable thermal conductivities at high porosities compared with their single three-dimensional framework and interpenetrated three-dimensional framework counterparts. Typically, high thermal conductivities are associated with low porosities; however, this work provides an alternative method to retain high porosities while drastically enhancing the thermal conductivity of the porous crystal. We attribute this to lower phonon-phonon scattering and vibrational hardening from supramolecular interactions that restrict atomic vibrational amplitudes, enhancing heat conduction. We also show this for realistic systems, with a two-dimensional interpenetrated framework of COF-1 achieving an order of magnitude increase in thermal conductivity when compared to its three-dimensional counterpart, COF-300. This introduces a new regime of materials design that combines ultrahigh thermal conductivities with ultralow mass densities via the interpenetration of two-dimensional porous crystals.