The exceptional photophysical properties of 3D organic–inorganic lead halide hybrids (OILHs) endow their significant potential for usage in optoelectronics, which has sparked intense research on novel 3D OILHs and associated applications. However, constructing new 3D OILHs based on large organic cations suffers from tough challenges due to the limitation of the Goldschmidt tolerance factor rule, let alone further explorations of their practical applications. Herein, a brand‐new 3D lead chloride hybrid, (1MPZ)Pb4Cl10·H2O (1, 1MPZ = 1‐methylpiperazine) is reported, featuring a dense 3D lead chloride framework made of the corner‐, edge‐, and face‐shared lead chloride polyhedra. 1 presents a broadband white light emission with a large Stokes shift and a nanosecond photoluminescence lifetime, which originates from radiative recombination of self‐trapped excitons (STEs) induced by the highly distorted structure. Such a reabsorption‐free and fast‐decayed STEs emission coupling with the dense 3D architecture further enables 1 with effective X‐ray scintillation with good sensitivity. Impressively, 1 also shows superior environmental and radiation stability. This study provides a new 3D OILH with appealing luminescence, not only expanding the 3D OILH family but also inspiring the exploitation of their optoelectronic applications.

2D chiral hybrid perovskites have recently emerged as outstanding semiconductor materials. However, most of the reported 2D chiral perovskites have limited structural types and contain high levels of toxic lead, which severely hinders their further applications. Herein, by using a mixed-cation strategy, an unprecedented type of lead-free cluster-based 2D chiral hybrid double perovskite derivatives are successfully obtained, [(R/S-PPA) 4 (IPA) 6 Ag 2 Bi 4 I 24 ]• 2H 2 O (1-R and 1-S), and [(R/S-PPA) 4 (n-BA) 6 Ag 2 Bi 4 I 24 ]•2H 2 O (2-R and 2-S) (R/S-PPA=R/S-1-phenylpropylamine; IPA=isopentylamine; n-BA=n-butylamine).Their inorganic skeletons are linked by binuclear {Bi 2 I 10 } and infinite chain {Ag 2 Bi 2 I 14 } ∞ , in which bismuth clusters and multiple coordination modes (e.g., tetrahedral AgI 4 and octahedral AgI 6 ) are introduced into the double perovskite system for the first time. This introduction induces distortion of the inorganic layer, which may facilitate the transfer of chirality from the chiral cations into achiral double perovskite skeletons. Further, circular dichroism measurements and circularly polarized light detection confirm their inherent chiral optical activities. In addition, 1-S exhibits an ultralow X-ray detection limit of 129.5 nGy s −1 , which is 42-fold lower than that of demands in regular medical diagnosis (5.5 µGy s −1 ). This study provides a pathway to construct novel type of lead-free cluster-based double perovskite derivatives.

Chiral three‐dimensional hybrid organic–inorganic perovskites (3D HOIPs) would show unique chiroptoelectronic performance due to the combination of chirality and 3D structure. However, the synthesis of 3D chiral HOIPs remains a significant challenge. Herein, we constructed a pair of unprecedented 3D chiral halide perovskitoids (R/S‐BPEA)EA6Pb4Cl15 (1‐R/S) (R/S‐BPEA=(R/S)‐1‐4‐Bromophenylethylammonium, EA=ethylammonium), in which the large chiral cations can be contained in the big “hollow” inorganic frameworks induced by mixing cations. Notably, 3D 1‐R/S shows natural chiroptical activity, as evidenced by its significant mirror circular dichroism spectra and the ability to distinguish circularly polarized light. Moreover, based on the unique 3D structure, 1‐S presents sensitive X‐ray detection performance with a low detection limit of 398 nGyair s−1, which is 14 times lower than the regular medical diagnosis of 5.5 μGyair s−1. In this work, 3D chiral halide perovskitoids provide a new route to develop chiral material in spintronics and optoelectronics.