How Strong Is the Hydrogen Bond in Hybrid Perovskites?
High Resolution Image Download MS PowerPoint Slide Hybrid organic–inorganic perovskites represent a special class of metal–organic framework where a molecular cation is encased in an anionic cage. The molecule–cage interaction influences phase stability, phase transformations, and the molecular dynamics. We examine the hydrogen bonding in four AmBX 3 formate perovskites: [Am]Zn(HCOO) 3, with Am + = hydrazinium (NH 2 NH 3 + ), guanidinium (C(NH 2 ) 3 + ), dimethylammonium (CH 3 ) 2 NH 2 +, and azetidinium (CH 2 ) 3 NH 2 + . We develop a scheme to quantify the strength of hydrogen bonding in these systems from first-principles, which separates the electrostatic interactions between the amine (Am + ) and the BX 3 – cage. The hydrogen-bonding strengths of formate perovskites range from 0.36 to 1.40 eV/cation (8–32 kcalmol –1 ). Complementary solid-state nuclear magnetic resonance spectroscopy confirms that strong hydrogen bonding hinders cation mobility. Application of the procedure to hybrid lead halide perovskites (X = Cl, Br, I, Am + = CH 3 NH 3 +, CH(NH 2 ) 2 + ) shows that these compounds have significantly weaker hydrogen-bonding energies of 0.09 to 0.27 eV/cation (2–6 kcalmol –1 ), correlating with lower order–disorder transition temperatures.