Reversible shape memory two-dimensional covalent organic frameworks

Two-dimensional covalent organic frameworks are a unique type of organic crystals with both weak layer-layer interaction and regular one-dimensional nanochannels. Therefore, it is possible to synthesize two-dimensional covalent organic frameworks with reversible stacking phases and thus pore sizes, which hold great potential applications in future nanoelectronics, nanoreactors, intelligent response, gas separation and storage. However, such a goal remains challenging up to now, because the slipped AA-stacking is the most thermodynamically stable phase. Here, we report the realization of shape memory two-dimensional covalent organic frameworks with reversible interlayer stacking sequences, of which AA and inclined phases are induced by the formation of hot ice and the strongly adsorbed organic molecules like Tetrahydrofuran inside the two-dimensional covalent organic frameworks confined nanochannels, respectively. Based on the reversible pore sizes and pore environments, we demonstrate the feasibility of the shape memory two-dimensional covalent organic frameworks in dynamically tunable permeability and intelligent response.