Carbon dioxide adsorption in open nanospaces formed by overlap of saponite clay nanosheets

Nanoscale open spaces formed by partial overlap of two-dimensional nanosheets in clays, abundantly and ubiquitously available, possess reactive molecular sites such as nanosheet edges in their interior. Here, the capture and storage of CO2 molecules in open spaces within saponite clay are explored by solid-state nuclear magnetic resonance coupled with open space analysis using positronium. CO2 physisorption occurs on the nanosheet surfaces inside the open spaces under ambient conditions. Thereby, CO2 molecules are activated by picking off weakly-bound oxygen from octahedral sites at the nanosheet edges and carbonate species are stabilized on the nanosheet surfaces. This instantaneous mineral carbonation and CO2 physisorption occurs in the absence of an energy-consumption process or chemical solution enhancement. This finding is of potential significance for CO2 capture and storage and presents an approach of environmentally friendly recycling of low contaminated soil in Fukushima. Sequestration of CO2 in geological reservoirs holds great potential, but ex situ mineral carbonation generally requires harsh, energy-intense conditions. Here the authors study CO2 physisorption at open nanospaces within overlapping nanosheets in saponite clay under ambient conditions.