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Data and materials availability: All data are available in the manuscript or supplementary information. All materials are available upon request to L.D. Methods Solution-phase synthesis of pure 2D halide perovskite sheets In this study, ten types of pure 2D halide perovskite sheets were synthesized via a quaternary solvent method.

This article presents a systematic study of the formation and thermal stability of Pt oxide species on sizeselected Pt nanoparticles (NPs) supported on SiO 2 , ZrO 2 , and TiO 2 thin films. The studies were carried out in ultrahigh vacuum (UHV) by temperature-dependent X-ray photoelectron spectroscopy (XPS) measurements and ex situ transmission electron microscopy and atomic force microscopy. The NPs were synthesized by inverse micelle encapsulation and oxidized in UHV at room temperature by an oxygen plasma treatment. For a given particle size distribution, the role played by the NP support on the stability of Pt oxides was analyzed. PtO 2 species are formed on all supports investigated after O 2 -plasma exposure. A two-step thermal decomposition (PtO 2 f PtO f Pt) is observed from 300 to 600 K upon annealing in UHV. The stability of oxidized Pt species was found to be enhanced on ZrO 2 under annealing treatments in O 2 . Strong NP/support interactions and the formation of Pt-Ti-O alloys are detected for Pt/TiO 2 upon annealing in UHV above 550 K but not under an identical treatment in O 2 . Furthermore, thermal treatments in both environments above 700 K lead to the encapsulation of Pt by TiO x . The final shape of the micellar Pt NPs is influenced by the type of underlying support as well as by the post-deposition treatment. Spherical Pt NPs are stable on SiO 2 , ZrO 2 , and TiO 2 after in situ ligand removal with atomic oxygen at RT. However, annealing in UHV at 1000 K leads to NP flattening on ZrO 2 and to the diffusion of Pt NPs into TiO 2 . The stronger the nature of the NP/support interaction, the more dramatic is the change in the NP shape (TiO 2 > ZrO 2 > SiO 2 ).

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Edges of two-dimensional (2D) halide perovskites are found to exhibit unusual properties such as enhanced photoluminescence lifetime and reduced photoluminescence emission energy. Here, we report the formation mechanism and the dynamic nature of edge states on exfoliated 2D halide perovskite thin crystals. In contrast to other 2D materials, the edge states in 2D perovskites are extrinsic and can be triggered by moisture with a concentration as low as ∼0.5 ppm. High-resolution atomic force microscopy and transmission electron microscopy characterizations reveal the width of the low-energy states is ∼40 nm wide. A temperature-dependent photoluminescence study suggests the edge states are a combination of several lower-energy states. Importantly, we demonstrate that the charge carriers on the dynamically formed edge states are not only long-lived but also highly mobile and can be conducted along the edges effectively with high mobilities of 5.4−7.0 cm 2 V −1 s −1 . This work provides significant insights on the origin of the edge states in 2D perovskites and provides routes to manipulate their optical and electrical properties through controlling their edges.

We report a new class of porous liquids (PLs) using internally functionalized metal–organic framework (MOF) particles as pore carriers and poly­(dimethylsiloxane) as bulky solvents. Using a generalizable noncovalent surface-initiated controlled radical polymerization technique, a series of isoreticular UiO-66 particles were dispersed in a liquid PDMS matrix with excellent homogeneity and colloidal stability. Benefiting from the inherent properties of PDMS, the PLs exhibit low vapor pressure, high thermal stability, and fluidity down to −35 °C. Attributed to the bulkiness of PDMS and its inherent high permeability, the sorption properties of the MOF fillers can be largely retained in their respective PLs as confirmed by low-pressure CO2, N2, Xe, and H2O sorption isotherms. The permanent porosity of the PLs can also be largely preserved even after 15 months of storage. Finally, we demonstrate that by tuning the molecular weight and polymer chain architecture of PDMS, it is possible to preserve the permanent porosity of a mesoporous MOF, MIL-101­(Cr), within a PL.

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