We report a family of cationic lead halide layered materials, formulated as [Pb X ] [ O C(CH) CO ] (X=F, Cl, Br), exhibiting pronounced broadband white-light emission in bulk form. These well-defined PbX-based structures achieve an external quantum efficiency as high as 11.8 %, which is comparable to the highest reported value (ca.9 %) for broadband phosphors based on layered organolead halide perovskites. More importantly, our cationic materials are ultrastable lead halide materials, which overcome the air/moisture-sensitivity problems of lead perovskites. In contrast to the perovskites and other bulk emitters, the white-light emission intensity of our materials remains undiminished after continuous UV irradiation for 30 days under atmospheric conditions (ca.60 % relative humidity). Our mechanistic studies confirm that the broadband emission is ascribed to short-range electron-phonon coupling in the strongly deformable lattice and generated self-trapped carriers.

No abstract

Figure 4. a) Guest exchange of TMOF-5(Br) with Eu 3+ .b)Emission spectra of 0.2 mol %-exchanged Eu 3+ @TMOF-5(Br) upon 340 nm excitation. c) CIE chromaticity coordinates of 0.2 mol %-exchanged Eu 3+ @TMOF-5(Br) and TMOF-5(Br).

Only a selected class of corrugated 2D hybrid lead halide perovskites exhibit broadband white-light emission from selftrapped excitons. Recently, we have discovered ultrastable layered lead halide photoemitters overcoming the stability problems of perovskites, despite in need of deep-UV irradiation to achieve photoluminescence quantum efficiency (PLQE) of over 10%. Herein, we have employed a robust, nonconjugated dicarboxylate ligand to pillar the cationic 1D [PbBr] + chains. The unique corrugated stacking of [PbBr] + chains facilitates the structural deformation to form self-trapped excitons, thus enabling an eightfold enhancement of PLQE over our previous reported bilayer bromoplumbate structures. The PLQE of 17.2% is not only among the highest in all of the layered lead halide white-light emitters, but overcoming the problem of our previous photoemitters requires deep-UV LED excitation. In addition, by tuning the stacking mode of the pillaring molecules, the chloride analog successfully incorporates a second photoluminescence center to the broadband emission from self-trapped excitons. The twocomponent emission strategy in [Pb 2 Cl 2 ][O 2 C (C 6 H 10 )CO 2 ] offers the intrinsic photoemitter to exhibit tunable cold-to-warm white light upon different excitation lights. The materials demonstrate high chemical robustness over a wide pH range (3−9) and undiminished photoluminescence in air upon UV irradiation for 30 days. Density functional theory calculations indicate that the broadband emission of both materials are induced by the structural deformation of [Pb 2 X 2 ] 2+ (X = Cl/Br) inorganic connectivity, which offers self-trapped electrons from Pb−Pb dimerization and self-trapped holes from Cl−Cl pairing in the excited states.

Organolead halide materials have shown promising optoelectronic properties that are suitable for light-emitting diodes (e.g., strong photoluminescence, narrow emission width, and high charge carrier mobility). However, the vast majority of them have no open porosity or open metal sites for host−guest interactions and are therefore not widely applicable in intrinsic fluorescent sensing of small molecules. Herein, we report a lead chloride-based metal−organic framework (MOF) with high porosity and stability and promising photoluminescent characteristics, performing as a sensitive, selective, and long-term stable fluorescence probe for NH 3 . For the first time, a homemade dynamic realtime photoluminescence monitoring system was developed, which showed that our haloplumbate-based MOF has an immediate response and an extremely low limit of detection (12 ppm) toward NH 3 . A variety of experimental characterization and theoretical calculations evidenced that the photoluminescence quenching was ascribed to the coordination between NH 3 guests and exposed Pb 2+ centers in MOFs. Moreover, a portable on-site smart NH 3 detector was designed based on this haloplumbate-MOF using a 3D printer, and the quantitative recovery experiment demonstrated the effective detection of NH 3 in the range of 15−150 ppm. This study opens a new pathway to design organolead halide-based MOFs to perform on-site chemical sensing of small molecules and shows their high potential to monitor safety concentrations of NH 3 in different industrial sites.