Advances in morphology-controlled alumina and its supported Pd catalysts: synthesis and applications.

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.

Dual-Stimuli-Responsive Modulation Organic Afterglow Based on N─H Proton Migration Mechanism.

Organic afterglow materials have significant applications in information security and flexible electronic devices with unique optical properties. It is vital but challenging to develop organic afterglow materials possessing controlled output with multi-stimuli-responsive capacity. Herein, dimethyl terephthalate (DTT) is introduced as a strong proton acceptor. The migration direction of N─H protons on two compounds Hs can be regulated by altering the excitation wavelength (Ex) or amine stimulation, thereby achieving dual-stimuli-responsive afterglow emission. When the Ex is below 300 nm, protons migrate to S1-2 DTT, where strong interactions induce phosphorescent emission of Hs, resulting in afterglow behavior. Conversely, when the Ex is above 300 nm, protons interact with the S0 DTT weakly and the afterglow disappears. In view of amine-based compounds with higher proton accepting capabilities, it can snatch proton from S1-2 DTT and redirect the proton flow toward amine, effectively suppressing the afterglow but obtaining a new redshifted fluorescence emission with Δλ over 200 nm due to the high polarity of amine. Moreover, it is successfully demonstrated that the applications of dual-stimuli-responsive organic afterglow materials in information encryption based on the systematic excitation-wavelength-dependent (Ex-De) behavior and amine selectivity detection.

Magneto-electrochemical method for chiral recognition of amino acid enantiomers.

Chiral recognition of enantiomers with identical mirror-symmetric molecular structures is important for the analysis of biomolecules, and it conventionally relies on stereoselective interactions in chiral chemical environments. Here, we develop a magneto-electrochemical method for the enhanced detection of chiral amino acids (AAs), that combines the advantages of the high sensitivity of electrochemiluminescent (ECL) biosensors and chirality-induced effects under a magnetic field. The ECL difference between L- and D-enantiomers can be amplified over 35-fold under a field of 3.5 kG, and the chiral discrimination can be achieved in dilute AA solutions down to the nM level. The field-dependent ECL and chronocoulometry measurements suggest that chiral AAs can lock the spins on their radicals and thus enlarge the ECL change under applied magnetic fields (magneto-ECL, MECL), which explains the field-enhanced chiral discrimination of AA enantiomers. Finally, a detailed protocol is demonstrated for the identification of unknown AA solutions, in which the species, chirality and concentration of AAs can be determined simultaneously from the 2D plots of the ECL and MECL results. This work benefits the development of field-assisted detection methods and represents a promising and universal strategy for the comprehensive analysis of chiral biomolecules.

Regulating Spin Density using TEMPOL Molecules for Enhanced CO2-to-Ethylene Conversion by HKUST-1 Framework Derived Electrocatalysts.

The selectivity of multicarbon products in the CO2 reduction reaction (CO2RR) depends on the spin alignment of neighboring active sites, which requires a spin catalyst that facilitates electron transfer with antiparallel spins for enhanced C-C coupling. Here, we design a radical-contained spin catalyst (TEMPOL@HKUST-1) to enhance CO2-to-ethylene conversion, in which spin-disordered (SDO) and spin-ordered (SO) phases co-exist to construct an asymmetric spin configuration of neighboring active sites. The replacement of axially coordinated H2O molecules with TEMPOL radicals introduces spin-spin interactions among the Cu(II) centers to form localized SO phases within the original H2O-mediated SDO phases. Therefore, TEMPOL@HKUST-1 derived catalyst exhibited an approximately two-fold enhancement in ethylene selectivity during the CO2RR at -1.8 V versus Ag/AgCl compared to pristine HKUST-1. In situ ATR-SEIRAS spectra indicate that the spin configuration at asymmetric SO/SDO sites significantly reduces the kinetic barrier for *CO intermediate dimerization toward the ethylene product. The performance of the spin catalyst is further improved by spin alignment under a magnetic field, resulting in a maximum ethylene selectivity of more than 50 %. The exploration of the spin-polarized kinetics of the CO2RR provides a promising path for the development of novel spin electrocatalysts with superior performance.

Boost the Circularly Polarized Phosphorescence of Chiral Organometallic Platinum Complexes by Hierarchical Assembly into Fibrillar Networks.

Circularly polarized luminescence (CPL)-active molecular materials have drawn increasing attention due to their promising applications for next-generation display and optoelectronic technologies. Currently, it is challenging to obtain CPL materials with both large luminescence dissymmetry factor (glum) and high quantum yield (Φ). A pair of enantiomeric N N C-type Pt(II) complexes (L/D)-1 modified with chiral Leucine methyl ester are presented herein. Though the solutions of these complexes are CPL-inactive, the spin-coated thin films of (L/D)-1 exhibit giantly-amplified circularly polarized phosphorescences with |glum| of 0.53 at 560 nm and Φair of ~50 %, as well as appealing circular dichroism (CD) signals with the maximum absorption dissymmetry factor |gabs| of 0.37-0.43 at 480 nm. This superior CPL performance benefits from the hierarchical formation of crystalline fibrillar networks upon spin coating. Comparative studies of another pair of chiral Pt(II) complexes (L/D)-2 with a symmetric N C N coordination mode suggest that the asymmetric N N C coordination of (L/D)-1 are favorable for the efficient exciton delocalization to amplify the CPL performance. Optical applications of the thin films of (L/D)-1 in CPL-contrast imaging and inducing CP light generation from achiral emitters and common light-emitting diode lamps have been successfully realized.

Adaptive Helical Chirality in Supramolecular Microcrystals for Circularly Polarized Lasing.

Chiral organic molecules offer a promising platform for exploring circularly polarized lasing, which, however, faces a great challenge that the spatial separation of molecular chiral and luminescent centers limits chiroptical activity. Here we develop a helically chiral supramolecular system with completely overlapped chiral and luminescent units for realizing high-performance circularly polarized lasing. Adaptive helical chirality is obtained by incorporating chiral agents into organic microcrystals. Benefiting from the efficient coupling of stimulated emission with the adaptive helical chirality, the supramolecular microcrystals enable high-performance circularly polarized lasing emission with dissymmetry factors up to ~ 0.7. This work opens up the way to rational design of chiral organic materials for circularly polarized lasing.

Switching from Thermally Activated Delayed Fluorescence in Single Crystals for Low-Threshold Laser to Room-temperature Phosphorescence in Amorphous-Film for Highly Efficient OLEDs.

Metal-organic phosphorescent complexes containing Ir or Pt are work horse in organic light-emitting diode (OLED) technology, which can harvest both singlet and triplet excitons in electroluminescence (EL) owing to strong heavy-atom effect. Recently, organic room-temperature phosphorescence (ORTP) have achieved high photoluminescence quantum yield (PLQY) in rigid crystalline state, which, however, is unsuitable for OLED fabrication, therefore leading to an EL efficiency far low behind those of metal-organic phosphorescent complexes. Here, we reported a luminescence mechanism switch from thermally activated delayed fluorescence (TADF) in single crystal microwires to ORTP in amorphous thin-films, based on a tert-butylcarbazole difluoroboron ß-diketonate derivative of DtCzBF2. Tightly packed and well-faceted single-crystal microwires exhibit aggregation induced emission (AIE), enabling TADF microlasers at 473 nm with an optical gain coefficient as high as 852 cm-1 . In contrast, loosely packed dimers of DtCzBF2 formed in guest-host amorphous thin-films decrease the oscillator strength of fluorescence transition but stabilize triplets for ORTP with a PLQY up to 61 %, leading to solution-processed OLEDs with EQE approaching 20 %. This study opens possibilities of low-cost ORTP emitters for high performance OLEDs and future low-threshold electrically injected organic semiconductor lasers (OSLs).

Tandem Catalysts Enabling Efficient C-N Coupling toward the Electrosynthesis of Urea.

The development of a methodology for synthesizing value-added urea (CO(NH2)2) via a renewable electricity-driven C-N coupling reaction under mild conditions is highly anticipated. However, the complex catalytic active sites that act on the carbon and nitrogen species make the reaction mechanism unclear, resulting in a low efficiency of C-N coupling from the co-reduction of carbon dioxide (CO2) and nitrate (NO3 -). Herein, we propose a novel tandem catalyst of Mo-PCN-222(Co), in which the Mo sites serve to facilitate nitrate reduction to the *NH2 intermediate, while the Co sites enhance CO2 reduction to carbonic oxide (CO), thus synergistically promoting C-N coupling. The synthesized Mo-PCN-222(Co) catalyst exhibited a noteworthy urea yield rate of 844.11 mg h-1 g-1, alongside a corresponding Faradaic efficiency of 33.90 % at -0.4 V vs. reversible hydrogen electrode (RHE). By combining in situ spectroscopic techniques with density functional theory calculations, we demonstrate that efficient C-N coupling is attributed to a tandem system in which the *NH2 and *CO intermediates produced by the Mo and Co active sites of Mo-PCN-222(Co) stabilize the formation of the *CONH2 intermediate. This study provides an effective avenue for the design and synthesis of tandem catalysts for electrocatalytic urea synthesis.

Host Surface-Induced Excitation Wavelength-Dependent Organic Afterglow.

The design and construction of organic afterglow materials is an attractive but formidably challenging task due to the low intersystem crossing efficiency and nonradiative decay. Here, we developed a host surface-induced strategy to achieve excitation wavelength-dependent (Ex-De) afterglow emission through a facile dropping process. The prepared PCz@dimethyl terephthalate (DTT)@paper system exhibits a room-temperature phosphorescence afterglow, with the lifetime up to 1077.1 ± 15 ms and duration time exceeding 6 s under ambient conditions. Furthermore, we can switch the afterglow emission on and off by adjusting the excitation wavelength below or above 300 nm, showing a remarkable Ex-De behavior. Spectral analysis demonstrated that the afterglow originates from the phosphorescence of PCz@DTT assemblies. The stepwise preparation process and detailed experiments (XRD, 1H NMR, and FT-IR analysis) proved the presence of strong intermolecular interactions between the carbonyl groups on the surface of DTT and the entire frame of PCz, which can inhibit the nonradiative processes of PCz to achieve afterglow emission. Theoretical calculations further manifested that DTT geometry alteration under different excitation beams is the main reason for the Ex-De afterglow. This work discloses an effective strategy for constructing smart Ex-De afterglow systems that can be fully exploited in a range of fields.

Room-Temperature Electrical Field-Enhanced Ultrafast Switch in Organic Microcavity Polariton Condensates.

Integrated electro-optical switches are essential as one of the fundamental elements in the development of modern optoelectronics. As an architecture for photonic systems exciton polaritons, hybrid bosonic quasiparticles that possess unique properties derived from both excitons and photons, have shown much promise. For this system, we demonstrate a significant improvement of emitted intensity and condensation threshold by applying an electric field to a microcavity filled with an organic microbelt. Our theoretical investigations indicate that the electric field makes the excitons dipolar and induces an enhancement of the exciton-polariton interaction and of the polariton lifetime. Based on these electric field-induced changes, a sub-nanosecond electrical field-enhanced polariton condensate switch is realized at room temperature, providing the basis for developing an on-chip integrated photonic device in the strong light-matter coupling regime.

Crystal-Liquid-Glass Transition and Near-Unity Photoluminescence Quantum Yield in Low Melting Point Hybrid Metal Halides.

Hybrid metal halides (HMHs) are a class of materials that combine extraordinary photophysical properties and excellent processability. Their chemical variability allows for the solid-liquid transition toward melt-processable HMHs. Herein, we report the design and synthesis of zero-dimensional HMHs [M(DMSO)6][SbCl6], where the isolated octahedra of [M(DMSO)6]3+ and [SbCl6]3- are alternatively aligned in the crystal structure. The luminescent center of [SbCl6]3- enables the photogeneration of self-trapped excitons, resulting in broadband photoluminescence with a large Stokes shift and a nearly 100% quantum yield. Meanwhile, the release of DMSO ligands from [M(DMSO)6]3+ is controlled by the M-O coordination and thus a low melting point of ∼90 °C is achieved for HMHs. Interestingly, the glass phase is obtained by melt quenching, with a sharp change in photoluminescence colors compared to the crystal phase of melt-processable HMHs. The robust crystal-liquid-glass transition opens a new avenue to tailoring structural disorder and optoelectronic performance in organic-inorganic materials.

High-Performance Organic Laser Semiconductor Enabling Efficient Light-Emitting Transistors and Low-Threshold Microcavity Lasers.

An organic light-emitting transistor (OLET) is a candidate device architecture for developing electrically pumped organic solid-state lasers, but it remains a critical challenge because of the lack of organic semiconductors that simultaneously possess a high solid-state emission efficiency (Φs), a high and balanced ambipolar mobility (µh,e), and a large stimulated emission cross-section. Here, we designed a molecule of 4,4'-bis(2-dibenzothiophenyl-vinyl)-biphenyl (DBTVB) and prepared its ultrathin single-crystal microplates with herringbone packing arrangements, which achieve balanced mobilities of µh = 3.55 ± 0.5 and µe = 2.37 ± 0.5 cm2 V-1 s-1, a high Φs of 85 ± 3%, and striking low-threshold laser characteristics. Theoretical and experimental investigations reveal that a strong electronic coupling and a small reorganization energy ensure efficient charge transport; meanwhile, the exciton-vibration effect and negligible π-π orbital overlap give rise to highly emissive H-aggregates and facilitate laser emission. Furthermore, OLET-based DBTVB crystals offer an internal quantum efficiency approaching 100% and a record-high electroluminescence external quantum efficiency of 4.03%.

Circularly Polarized Lasing from a Microcavity Filled with Achiral Single-Crystalline Microribbons.

Organic circularly polarized (CP) lasers have received increasing attention due to their future photoelectric applications. Here, we demonstrate a CP laser from a pure organic crystal-filled microcavity without any chiral molecules or chiral structures. Benefited from the giant anisotropy and excellent laser gain of organic crystals, optical Rashba-Dresselhaus spin-orbit coupling effect can be induced and is conductive to the CP laser in such microcavities. The maximum dissymmetry factor of the CP lasing with opposite helicities reachs 1.2. Our strategy may provide a new idea for the design of CP lasers towards future 3D laser displays, information storage and other fields.

Continuous-Wave Raman Lasing from Metal-Linked Organic Dimer Microcrystals.

Stimulated Raman scattering offers an alternative strategy to explore continuous-wave (c.w.) organic lasers, which, however, still suffers from the limitation of inadequate Raman gain in organic material systems. Here we propose a metal-linking approach to enhance the Raman gain of organic molecules. Self-assembled microcrystals of the metal linked organic dimers exhibit large Raman gain, therefore allowing for c.w. Raman lasing. Furthermore, broadband tunable Raman lasing is achieved in the organic dimer microcrystals by adjusting excitation wavelengths. This work advances the understanding of Raman gain in organic molecules, paving a way for the design of c.w. organic lasers.

Electrically Amplified Circularly Polarized Luminescence by a Chiral Anion Strategy.

The development of circularly polarized electroluminescence (CPEL) is currently hampered by the high difficulty and cost in the syntheses of suitable chiral materials and the notorious chirality diminishment issue in electrical devices. Herein, diastereomeric IrIII and RuII complexes with chiral (±)-camphorsulfonate counteranions are readily synthesized and used as the active materials in circularly polarized light-emitting electrochemical cells to generate promising CPELs. The addition of the chiral ionic liquid (±)-1-butyl-3-methylimidazole camphorsulfonate into the active layer significantly improves the device performance and the electroluminescence dissymmetry factors (≈10-3 ), in stark contrast to the very weak circularly polarized photoluminescence of the spin-coated films of these diastereomeric complexes. Control experiments with enantiopure IrIII complexes suggest that the chiral anions play a dominant role in the electrically-induced amplification of CPELs.

A Paramagnetic Compass Based on Lanthanide Metal-Organic Framework.

Macroscopic compass-like magnetic alignment at low magnetic fields is natural for ferromagnetic materials but is seldomly observed in paramagnetic materials. Herein, we report a "paramagnetic compass" that magnetically aligns under ∼mT fields based on the single-crystalline framework constructed by lanthanide ions and organic ligands (Ln-MOF). The magnetic alignment is attributed to the Ln-MOF's strong macroscopic anisotropy, where the highly-ordered structure allows the Ln-ions' molecular anisotropy to be summed according to the crystal symmetry. In tetragonal Ln-MOFs, the alignment is either parallel or perpendicular to the field depending on the easiest axis of the molecular anisotropy. Reversible switching between the two alignments is realized upon the removal and re-adsorption of solvent molecules filled in the framework. When the crystal symmetry is lowered in monoclinic Ln-MOFs, the alignments become even inclined (47°-66°) to the field. These fascinating properties of Ln-MOFs would encourage further explorations of framework materials containing paramagnetic centers.

Excitation-Wavelength-Dependent Organic Long-Persistent Luminescence Originating from Excited-State Long-Range Proton Transfer.

Stimuli-responsive functional luminescent materials with tunable color and long-persistent emission have emerged as a powerful tool in information encryption, anticounterfeiting, and bioelectronics. Herein, we prove a novel strategy for manipulating the proton transfer pathways in the salicylaldehyde derivative EQCN solutions/powder to produce excitation wavelength-dependent (Ex-De) performances with switchable emissions (blue-sky, green, and orange). The experiments and theoretical results demonstrated that the different luminous colors are originated from enol (E) form (blue-sky), Keto-1 (K1) form (orange) through the excited-state intramolecular proton transfer (ESIPT) process, and Keto-2 (K2) form (green) through the excited-state long-range proton transfer (ESLRPT) process. We leverage synergistic effects between the dopant and matrix (dimethyl terephthalate, DTT) to manipulate the excited-state proton transfer pathway in EQCN@DTT mixture powders to generate Ex-De long-persistent luminescence (Ex-De-LPL), which can be well applied in multilevel information encryption. This strategy not only paves an intriguing way for the construction and preparation of pure organic Ex-De materials but also offers a guideline for developing LPL materials based on ESLRPT processes.

Engineering O-O Species in Boron Nitrous Nanotubes Increases Olefins for Propane Oxidative Dehydrogenation.

Boron nitride (BN) has been widely studied as an efficient catalyst for oxidative propane dehydrogenation (OPDH). Oxygen-containing boron species (e.g., BO·, B(OH)xO3-x) are generally considered as the active centers in BN for OPDH. Here, we show an effective progressive substitution strategy toward the development of boron-oxygen-nitrogen nanotubes (BONNTs) enriched with O-O species as a highly active, selective, and stable catalyst for OPDH. At 525 °C, an olefin yield of 48.6% is achieved over BONNTs with a propane conversion of 64.4%, 2.8 times that of boron nitrogen nanotubes (BNNTs). Even after reaction for 150 h (475 °C), BONNTs exhibit good olefin yield. Both the B(OH)xO3-x and O-O species that coexist in the BONNT catalyst are demonstrated as active centers, which differs from the B(OH)xO3-x one in BNNTs. Based on catalytic results, propane and oxygen alternate treatment experiments, and theoretical calculations, the O-O center is more favorable for producing both propylene (C3=) and ethylene (C2=), which experiences a dehydration pathway and two possible reaction paths with a lower energy barrier to yield olefins, while B(OH)xO3-x is mainly responsible for producing few C3=.

3D-Printed Möbius Microring Lasers: Topology Engineering in Photonic Microstructures.

Manipulating photons in artificially structured materials is highly desired in modern photonic technology. Nontrivial topological structures are rapidly emerging as a state-of-art platform for achieving unprecedented fascinating phenomena of photon manipulation. However, the current studies mainly focus on planar structures, and the fabrication of photonic microstructures with specific topological geometric features still remains a great challenge. Extending the topological photonics to 3D microarchitectures is expected to enrich the photon manipulation capabilities and further advance the topological photonic devices. Here, a femtosecond laser direct writing technique is employed to fabricate 3D topological Möbius microring resonators from dye-doped polymer. The high-quality-factor Möbius microring resonator supports a unique spin-orbit coupled lasing at very low threshold. Due to the spin-orbit coupling induced geometric/Berry phase, the Möbius microrings, in striking contrast with ordinary microrings, output laser signals with all polarization states. The manipulation of miniaturized coherent light sources in the fabricated Möbius microrings represents a significant step forward toward 3D topological photonics that offers a novel design philosophy for functional photonic and optoelectronic devices.

Optically Triggering and Monitoring Single-Cell-Level Metabolism Using Ormosil-Decorated Ultrathin Fibers.

The integration of biological components and artificial devices requires a bio-machine interface that can simultaneously trigger and monitor the activities in biosystems. Herein, we use an organically modified silicate (ormosil) composite coating containing a light-responsive nanocapsule and a fluorescent bioprobe for reactive oxygen species (ROS) to decorate ultrathin optical fibers, namely, ormosil-decorated ultrathin fibers (OD-UFs), and demonstrate that these OD-UFs can optically trigger and monitor the intracellular metabolism activities in living cells. The sizes and shapes of UF tips were finely controlled to match the dimension and mechanical properties of living cells. The increased elasticity of the ormosil coating of OD-UFs reduces possible mechanical damage during the cell membrane penetration. The light-responsive nanocapsule was physically absorbed on the surface of the ormosil coating and could release a stimulant to trigger the metabolism activities in cells upon the guided laser through OD-UFs. The fluorescent bioprobe was covalently linked with the ormosil matrix for monitoring the intracellular ROS generation, which was verified by the in vitro experiments on the microdroplets of a hydrogen peroxide solution. Finally, we found that the living cells could maintain most of their viability after being inserted with OD-UFs, and the intracellular metabolism activities were successfully triggered and monitored at the single-cell level. The OD-UF provides a new platform for the investigation of intracellular behaviors for drug stimulations and represents a new proof of concept for a bio-machine interface based on the optical and chemical activities of organic functional molecules.