CO 2 Induces Symmetry Breaking in Layered Dipeptide Crystals.

Control of symmetry breaking of materials provides large opportunities to regulate their properties and functions. Herein, we report breaking the symmetry of layered dipeptide crystals by utilizing CO to induce the adjacent monomolecular layers to stack from the opposite to the same direction. The role of CO is to cover the interlayer interaction sites and force the dipeptides to adsorb at asymmetric positions. Further, the dipeptide crystals exhibit far superior piezoelectricity after symmetry breaking and the piezoelectric voltage generated from the dipeptide-based generators becomes more than 500 % higher than before. This work reveals a potential route to engineer structures and properties of layered materials and provides a deep insight into the control of non-covalent interactions.