Mechanochemistry is a green, solid-state, re-emerging synthetic technique that can rapidly form complex molecules and materials without exogenous heat or solvent(s). Herein, we report the application of solvent-free mechanochemical ball milling for the synthesis of metal halide perovskites, to overcome problems with solution-based syntheses. We prepared phase-pure, air-sensitive CsSnX 3 (X = I, Br, Cl) and its mixed halide perovskites by mechanochemistry for the first time by reactions between cesium and tin(II) halides. Notably, we report the sole examples where metastable, high-temperature phases like cubic CsSnCl 3 , cubic CsPbI 3 , and trigonal FAPbI 3 were accessible at ambient temperatures and pressures without post-synthetic processing. The perovskites can be prepared up to ''kilogram scales.'' Lead-free, all-inorganic photodetector devices were fabricated using the mechanosynthesized CsSnBr 1.5 Cl 1.5 under solvent-free conditions and showed 10-fold differences between on-off currents. We highlight an essentially solvent-free, general approach to synthesize metastable compounds and fabricate photodetectors from commercially available precursors.

Two‐dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1‐hexadecylammonium (HDA) between the inorganic layers. We observed visible‐light absorption, narrow‐band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Owing to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline‐2‐carboxylic acids. (HDA)2PbI4 or (HDA)2SnI4 were investigated as photoredox catalysts for these reactions, and quantitative conversion and high yields were observed with the former.

Sodium hydride (NaH) has been commonly used as a Brønsted base in chemical syntheses, while it has rarely been employed to add hydride (H(-) ) to unsaturated electrophiles. We previously developed a procedure to activate NaH through the addition of a soluble iodide source and found that the new NaH-NaI composite can effect even stereoselective nucleophilic hydride reductions of nitriles, imines, and carbonyl compounds. In this work, we report that mixing NaH with NaI or LiI in tetrahydrofuran (THF) as a solvent provides a new inorganic composite, which consists of NaI interspersed with activated NaH, as revealed by powder X-ray diffraction, and both solid-state NMR and X-ray photoelectron spectroscopies. DFT calculations imply that this remarkably simple inorganic composite, which is comprised of NaH and NaI, gains nucleophilic hydridic character similar to covalent hydrides, resulting in unprecedented and unique hydride donor chemical reactivity.

Through the precoating of TiO 2 on carbon fiber sheet and the subsequent hydrothermal reaction of the coated species with NaOH and tetrabutyl titanate, we successfully demonstrated the engineering growth of TiO 2 nanofibers on carbon fiber sheet. The resulting cloth exhibits excellent flexibility and enables robust, large-area ($300 cm 2 ) fabrication, representing a significant advantage over previous brittle, small area nanofibrous macroscopic structures. The adsorption and photodecomposition of Rhodamine B in water showed that the resulting cloth is very convenient for the purification of contaminated water owing to its combined adsorption and cleaning function. This work provides new insight into the construction of a large area, flexible and robust water purification membrane material.

Two‐dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1‐hexadecylammonium (HDA) between the inorganic layers. We observed visible‐light absorption, narrow‐band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Owing to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline‐2‐carboxylic acids. (HDA)2PbI4 or (HDA)2SnI4 were investigated as photoredox catalysts for these reactions, and quantitative conversion and high yields were observed with the former.