Rational design of enantiomeric lead-free double perovskites by achiral-chiral cation intercalation

Chiral lead-free halide double perovskites A4BIBIIIX8 (A = chiral organic cations) are highly desirable because of their environmental friendliness and chiral functionality, but they are rarely reported. Herein, through the strategy of chiral-achiral cation intercalation, we rationally design enantiomeric lead-free halide double perovskites with the formula (A)2(A′)2BIBIIIX8 (A = chiral organic cations, A′ = achiral organic cations). Experimentally, on the basis of the reported achiral LHDP (BA)4AgBiBr8, we obtained a series of six enantiomeric lead-free halide double perovskites—(R-PPA)2(BA)2AgBiBr8 and (S-PPA)2(BA)2AgBiBr8, (R-PPA)2(BrPA)2AgBiBr8 and (S-PPA)2(BrPA)2AgBiBr8, and (R-PPA)2(BrEA)2AgBiBr8 and (S-PPA)2(BrEA)2AgBiBr8 (PPA = 1-phenylpropylamine, BA = n-butylaminium, BrPA = 3-bromopropylaminium, BrEA = 2-bromoethylaminium)—demonstrating the feasibility of this synthesis strategy. Chiral cations and achiral cations arrange alternatingly in the interlayer and connect by diverse noncovalent intermolecular interactions, such as CH···π, π···π, and CH···Br. Consequently, the diverse arrangements and combinations of chiral A and achiral A′ cations bring abundant chiral functionalities and robust circular dichroism signals.