H/F Substitution Achieved Enantiomeric Organic Inorganic Hybrid Perovskites and Trigonal Structure [DMFP] 3 (CdBr 3 )(CdBr 4 ).

Organic-inorganic hybrid perovskites (OIHPs) have been emerging as a hot research topic due to their potential applications in energy storage, semiconductors, and electronic devices. Herein, we systematically investigated the synthesis and phase transition behaviors of the enantiomeric OIHPs, ( R ) and ( S )- N , N -dimethyl-3-fluoropyrrolidinium cadmium bromide ([DMFP][CdBr 3 ]), and the hybrid trigonal structure [DMFP] 3 (CdBr 3 )(CdBr 4 ). The enantiomers have a mirror-symmetric structure and enhanced solid-state phase transition points of 417 and 443 K, in contrast to the nonfluorinated parent compound, N , N -dimethyl-pyrrolidinium cadmium bromide ([DMP][CdBr 3 ], 385 K). Moreover, racemic H/F substitution on the pyrrolidinium cations leads to the formation of a trigonal compound, showing above-room-temperature structural phase transition and dominant ferroelasticity. This work discovers chiral enantiomeric OIHPs through H/F substitution, demonstrating a useful chemical synthesis strategy for exploring novel phase transition materials.