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 AmBX3 formate perovskites: [Am]Zn(HCOO)3, with Am+ = hydrazinium (NH2NH3+), guanidinium (C(NH2)3+), dimethylammonium (CH3)2NH2+, and azetidinium (CH2)3NH2+. 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 BX3- 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+ = CH3NH3+, CH(NH2)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.
Bibliographical noteFunding Information:
K.L.S. is supported by ERC grant no. 277757. K.T.B. is funded by EPSRC (EP/M009580/1 and EP/J017361/1). We acknowledge computing support from the U.K. national supercomputing service (Archer) via membership of the U.K. Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202), and from the University of Bath computing services (Balena). A.C.F. acknowledges the Sims Scholarship (Cambridge) for funding as well as John Griffin (Lancaster University) for support and useful discussions. A.C.F. and G.K. thank THMCRFC for support, and A.K.C. thanks the Ras al Khaimah Centre for Advanced Materials. Calculations in CASTEP were performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell, Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council.
© 2017 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physical and Theoretical Chemistry