Large pyroelectric and thermal expansion coefficients in the [(CH3)2NH2]Mn (HCOO)3 metal-organic framework

The [(CH₃)₂NH₂]Mn(HCOO)₃ perovskite metal-organic framework exhibits a first-order ferroelectric phase transition with a high polarization at T_c ∼ 192 K, induced by the order-disorder transition of hydrogen bonds. Accompanying this sharp phase transition, a huge pyroelectric coefficient with a peak value of 5.16 × 10^-2 C/m² K is detected. In addition, there is a large lattice expansion along the [012] direction at T_c, resulting in a giant linear thermal expansion coefficient as high as 35 000 ppm/K. These striking results indicate that ferroelectric metal-organic frameworks combing both merits of inorganic and organic compounds hold a great potential in generating superior pyroelectric and thermal expansion properties.