H/F Substitution Achieved Enantiomeric Organic Inorganic Hybrid Perovskites and Trigonal Structure [DMFP]₃(CdBr₃)(CdBr₄)

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][CdBr3]), and the hybrid trigonal structure [DMFP](3) (CdBr3)(CdBr4). 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][CdBr3], 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.