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In the field of organic light-emitting diodes (OLEDs), research interests focus on making the optically dark triplet excitons shine in order to increase the electro-optic conversion efficiency of devices. In this work, two kinds of phenazine compounds, i.e. dibenzo[a,c]phenazine (DBP) and tribenzo[a,c,i]phenazine (TBP), were synthesized and used as model compounds to regulate the emission efficiency of the dark triplet excitons by chemical modification. Charge-transfer induced ultrafast intersystem crossing (CT-ISC) with a time constant of ∼1 ps was observed for these two phenazine derivatives upon photoexcitation with a high triplet yield of 77.1% for DBP and 58.7% for TBP. The triplet excited states of DBP can produce ultra-long phosphorescence with lifetime as long as 318 ms at 77 K. The quantum yield for phosphorescence (ΦP) is determined to be 8.45%. In sharp contrast, the triplet-excited 3TBP* undergoes an efficient reverse intersystem crossing (RISC) process, resulting in bright delayed fluorescence emission with negligible phosphorescence. A controllable luminescence behavior from the triplet states between fluorescence and phosphorescence in phenazine derivatives is demonstrated. Theoretical calculations reveal that the structure-dependent triplet evolution is due to the charge-transfer induced energy level alignment within these compounds. Our results may have potential applications in the design of OLEDs and high triplet yield pure organic materials. [ABSTRACT FROM AUTHOR]

Alumina materials, as one of the cornerstones of the modern chemical industry, possess physical and chemical properties that include excellent mechanical strength and structure stability, which also make them highly suitable as catalyst supports. Alumina-supported Pd-based catalysts with the advantages of exceptional catalytic performance, flexible regulated surface metal/acid sites, and good regeneration ability have been widely used in many traditional chemical industry fields and have also shown great application prospects in emerging fields. This review aims to provide an overview of the recent advances in alumina and its supported Pd-based catalysts. Specifically, the synthesis strategies, morphology transformation mechanisms, and structural properties of alumina with various morphologies are comprehensively summarized and discussed in-depth. Then, the preparation approaches of Pd/Al2O3 catalysts (impregnation, precipitation, and other emerging methods), as well as the metal–support interactions (MSIs), are revisited. Moreover, Some promising applications have been chosen as representative reactions in fine chemicals, environmental purification, and sustainable development fields to highlight the universal functionality of the alumina-supported Pd-based catalysts. The role of the Pd species, alumina support, promoters, and metal–support interactions in the enhancement of catalytic performance are also discussed. Finally, some challenges and upcoming opportunities in the academic and industrial application of the alumina and its supported Pd-based are presented and put forward. [ABSTRACT FROM AUTHOR]

Three hydrogen-bonded organic–inorganic frameworks (HOIFs) are synthesized. Along with full characterization and a comparison with similarly synthesized deuterated counterparts, we reveal that hydrogen-bond interactions of the HOIFs dominate the thermostability, porosity and selectivity in dye filtration on alumina membranes. [ABSTRACT FROM AUTHOR]

Acid-promoted efficient, site- and stereo-selective bicyclization of alkynes to polycyclic compounds (benzobicyclo[3.2.1]octanes) was realized with atom- and step-economy. The reaction proceeded through two C–C bonds formed on remote alkyl C–H bonds via twice long-distance cationic rearrangement. [ABSTRACT FROM AUTHOR]

The invention and development of the laser have revolutionized science, technology, and industry. Metal halide perovskites are an emerging class of semiconductors holding promising potential in further advancing the laser technology. In this Review, we provide a comprehensive overview of metal halide perovskite lasers from the viewpoint of materials chemistry and engineering. After an introduction to the materials chemistry and physics of metal halide perovskites, we present diverse optical cavities for perovskite lasers. We then comprehensively discuss various perovskite lasers with particular functionalities, including tunable lasers, multicolor lasers, continuous-wave lasers, single-mode lasers, subwavelength lasers, random lasers, polariton lasers, and laser arrays. Following this a description of the strategies for improving the stability and reducing the toxicity of metal halide perovskite lasers is provided. Finally, future research directions and challenges toward practical technology applications of perovskite lasers are provided to give an outlook on this emerging field. [ABSTRACT FROM AUTHOR]

Two series of cocrystals with the formula Ln(NO3)5·H2TPPZ (Ln = Eu, Tb, Er and Y, TPPZ = 2,3,5,6-tetra-2-pyridinylpyrazine) have been designed and synthesized. Utilizing single crystal structure parsing, we demonstrate how weak hydrogen bonding interactions between lanthanide nitrates and organic molecules stabilize their cocrystal structures. The lanthanide contraction effect is also proposed to help determine the Ln–O bond regularity, hence rationalizing the stability and structural variation of the cocrystals. Furthermore, the luminescence properties of these cocrystals were analyzed in detail. We found an interesting result of decent red fluorescence of the 1-Eu cocrystal complex. [ABSTRACT FROM AUTHOR]

A novel palladium catalyzed hydroxylation of unactivated aliphatic C(sp3)–H bonds was successfully developed. Different from conventional methods, water serves as the hydroxyl group source in the reaction. This new reaction demonstrates good reactivity and broad functional group tolerance. The C–H hydroxylated products can be readily transformed into various highly valuable chemicals via known transformations. Based on experimental and theoretical studies, a mechanism involving the Pd(ii)/(iv) pathway is proposed for this hydroxylation reaction. [ABSTRACT FROM AUTHOR]