Topochemical reactions have led to great progress in the discovery of new metastable compounds with novel chemical and physical properties. With these reactions, the overall crystal structure of the host material is generally maintained. Here we report a topochemical synthesis of a hexagonal nitride hydride, h-Ca3CrN3H, by heating an orthorhombic nitride, o-Ca3CrN3, under hydrogen at 673 K, accompanied by a rotational structural transformation. The hydrogen intercalation modifies the Ca-N rock-salt-like atomic packing in o-Ca3CrN3 to a face-sharing octahedral chain in h-Ca3CrN3H, mimicking a 'hinged tessellation' movement. In addition, the h-Ca3CrN3H exhibited stable ammonia synthesis activity when used as a catalyst.
KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: This work was supported by the Japan Society for Promotion of Science (JSPS) the Grant-in-Aid for Specially Promoted Research (22H04914), JSPS Core-to-Core Program (Grant JPJSCCA20200004), CREST (JPMJCR20R2) and JSPS KAKENHI (21J15834). The financial support for this work was also provided by the King Abdullah University of Science and Technology (KAUST). The synchrotron-diffraction measurements were carried out by the project approval (nos. 2021A1595 and 2021B1815).