As illumination is a fundamental human need, the exploration of illumination sources possessing high efficiency and broadband white-light emission is highly desirable. Zero-dimensional (0D) metal halide compounds are promising candidates, and some lead-free antimony-containing compounds exhibit bimodal white-light emissions. However, their origins are still unclear. To solve this issue, we designed and prepared a new family of 0D metal halide compounds consisting of [M(18-crown-6)] + (M = NH 4 , Rb) and SbX 5 2− (X = Cl, Br) units. We found that the emission profiles of 0D compounds are distinct to and well separated from that of 18-crown-6 ether, excluding the intraligand charge transfer mechanism proposed in several reports. Femtosecond transient absorption data and the compositional dependence of photophysical properties imply that bimodal white-light emission is induced by both singlet state and triplet state of the self-trapped excitons ( 1 STE and 3 STE) coupled to metal halides. These 0D compounds are also very efficient emitters, with a white-light photoluminescence quantum yield as high as 54%.

The anion-exchangeable family of layered rare-earth hydroxides RE2(OH)5X·nH2O (LREH-X, RE = rare-earth elements such as Y, X– = monovalent anions, n ≈ 1.5) exhibits considerable potential in various applications. However, their structures remain controversial or even unresolved. Herein, a comprehensive study involving 1D and 2D 89Y solid-state NMR spectroscopy, powder X-ray/neutron diffraction, and periodic DFT calculations was conducted to solve the structure of LYH-X (X– = Cl–, Br–, NO3 –), one of the most extensively used and studied subjects of the LREH-X family. The anion-exchange behaviors were then investigated, and the results clearly demonstrate strong influences of X– on the structure and anion exchange: first, the structure of LYH-Cl is orthorhombic P21212, whereas LYH-Br and LYH-NO3 are monoclinic P21 structures; second, the conversion from the high-symmetry P21212 phase to the low-symmetry P21 phase can be conducted quite well via anion exchange, but not vice versa; finally, the foreign anions site-specifically interact with host layers. Such strong influences are the unique characteristics of LYH-X and thus should be considered in future studies and applications of these materials.

Ethanol transformation with high product selectivity is a great challenge, especially for high weight molecules. Here, we show a combination study of kinetic, thermodynamic, and in situ spectroscopy measurements to probe the selective upgrading of ethanol over lamellar Ce(OH)SO 4 •xH 2 O catalysts, with 60− 70% Ce 3+ preserved during the catalysis. High methyl phenols (MPs) selectivity at ∼80% within condensation products was achieved at ∼50% condensation yield (3.0 kPa C 2 H 5 OH, 15 kPa H 2 , Ar balanced, 693 K, 1 atm, gas hourly space velocity (GHSV) ∼5.4 min −1 ), with acetaldehyde, acetone, 4-heptanone, and 2pentanone as the key reaction intermediates. Kinetic measurements with the assistance of isotope labeling proved that MPs generated from the kinetically relevant step (KRS) of C−C bond coupling of enolate nucleophilically attacks surface C 2 H 4 O following a Langmuir−Hinshelwood model. Low ethanol and water pressures and high acetaldehyde and hydrogen pressures were proved to be favored for MPs generation rather than dehydration, in which hydrogen could reduce the amount of lattice oxygen and facilitate the preparation of MPs while water and ethanol both compete with acetaldehyde for active sites during catalysis. On the basis of in situ X-ray diffraction (XRD), quasi-in situ X-ray photoelectron spectroscopy (XPS), and Raman characterizations, the Ce(OH)SO 4 crystal structure was proved to be maintained along with ethanol activation, and the Ce 3+ −OH Lewis acid−base pair was proved to be the active species for the selective C−C bond coupling. The KRS assumption was also supported by the apparent activation energy assessment within the reaction network on dehydration, dehydrogenation, aldol condensation, and cyclization and a series of negligible kinetic isotope effects (KIEs). This system can be easily extended to some other systems related to C−C bond coupling and is attracting attention on converting oxygenate platform molecules over lanthanide species.

The effect of pore structures in porous catalysts on the catalytic behavior of guest molecules has been discussed for decades. However, there is still no clear evidence to show that the guest molecule is stably confined within the designed local environment. The local concentration of reactants caused by the confined space may affect the catalytic reaction. Herein, we show a probe study that analyzes the influence of the primary pore size on the product selectivity in the aldol condensation of acetaldehyde/ethanol mixtures (C2), in which the reactants have been shown to be thermodynamically stable in relatively large pores (10–30 Å) of metal–organic framework (MOF) catalysts (such as UiO-66, NU-1000, NU-901, UiO-67, etc.) rather than the micropores (<10 Å) during the condensation of the C2 molecule, which is explained by solid-state nuclear magnetic resonance ssNMR analysis. This actually suggests that the promoting effect of the primary pore on ethanol upgrading selectivity is only feasible once the guest molecule has been able to stabilize within the pore during catalysis.