Unusually stable ~100-fold reversible and instantaneous swelling of inorganic layered materials

Cells can swell or shrink in certain solutions; however, no equivalent activity has been observed in inorganic materials. Although lamellar materials exhibit increased volume with increase in the lamellar period, the interlamellar expansion is usually limited to a few nanometres, with a simultaneous partial or complete exfoliation into individual atomic layers. Here we demonstrate a large monolithic crystalline swelling of layered materials. The gallery spacing can be instantly increased ~100-fold in one direction to ~90 nm, with the neighbouring layers separated primarily by H2O. The layers remain strongly held without peeling or translational shifts, maintaining a nearly perfect three-dimensional lattice structure of >3,000 layers. First-principle calculations yield a long-range directional structuring of the H2O molecules that may help to stabilize the highly swollen structure. The crystals can also instantaneously shrink back to their original sizes. These findings provide a benchmark for understanding the exfoliating layered materials. Cells are known to swell and shrink in certain solutions, however no inorganic equivalent has been observed to date. Here, the authors demonstrate 100-fold reversible swelling of crystalline lamellar materials, which may be attributed to the long-range directional structuring of intercalated water molecules.