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.