Design of hyperporous graphene networks and their application in solid-amine based carbon capture systems

Abstract

We demonstrate a simple and fully scalable method for obtaining hierarchical hyperporous graphene networks of ultrahigh total pore volume by thermal-shock exfoliation of graphene-oxide (exfGO) at a relatively mild temperature of 300 °C. Such pore volume per unit mass has not previously been achieved in any type of porous solid. We find that the amount of oxidation of starting graphene-oxide is the key factor that determines the pore volume and surface area of the final material after thermal shock. Specifically, we emphasize that the development of the hyperporosity is directly proportional to the enhanced oxidation of sp² CC to form CO/COO. Using our method, we reproducibly synthesized remarkable meso-/macro-porous graphene networks with exceptionally high total pore volumes, exceeding 6 cm³ g⁻¹. This is a step change compared to ≤3 cm³ g⁻¹ in conventional GO under similar synthetic conditions. Moreover, a record high amine impregnation of >6 g g⁻¹ is readily attained in exfGO samples (solid-amine@exfGO), where amine loading is directly controlled by the pore-structure and volume of the host materials. Such solid-amine@exfGO samples exhibit an ultrahigh selective flue-gas CO₂ capture of 30–40 wt% at 75 °C with a working capacity of ≈25 wt% and a very long cycling stability under simulated flue-gas stream conditions. To the best of our knowledge, this is the first report where a graphene-oxide based hyperporous carbon network is used to host amines for carbon capture application with exceptionally high storage capacity and stability.