Developing pure organic materials with ultralong lifetimes is attractive but challenging. Here we report a concise chemical approach to regulate the electronic configuration for phosphorescence ...enhancement. After the introduction of d–pπ bonds into a phenothiazine model system, a phosphorescence lifetime enhancement of up to 19 times was observed for DOPPMO, compared to the reference PPMO. A record phosphorescence lifetime of up to 876 ms was obtained in phosphorescent phenothiazine. Theoretical calculations and single‐crystal analysis reveal that the d–pπ bond not only reduces the (n, π*) proportion of the T1 state, but also endows the rigid molecular environment with multiple intermolecular interactions, thus enabling long‐lived phosphorescence. This finding makes a valuable contribution to the prolongation of phosphorescence lifetimes and the extension of the scope of phosphorescent materials.
Glowing longer: The introduction of d–pπ bonds was utilized to prolong organic phosphorescence lifetimes. The luminogen N‐acetyl phenothiazine‐S,S‐dioxide (DOPEO) shows an ultralong lifetime of 876 ms with a phosphorescence quantum yield of 8.2 %, which are the highest values among phenothiazine‐based organic phosphorescent substances.
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Porous covalent organic frameworks (COFs), as an emerging material, have the characteristics of high stability, large series of components, easy synthesis, modification, and adjustable amplitude. ...They have the potential to become good catalysts. Bromine, as a halogen, has attracted intensive interest for the modification of photocatalysts for photocatalytic reactions. It is feasible to enhance the activity and selectivity of the material by facile functionalization of the reticular parent structure′s electron‐withdrawing groups. In addition, the conjugation effect of bromine, further delocalizing the electrons of the COF, is beneficial to the progress of many photocatalytic reactions. Reports on the modification of COFs by bromine functional groups to improve the catalytic performance have not been found so far. Here, TAPP 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin and 2,5‐dibromo‐1,4‐benzenedialdehyde instead of terephthalaldehyde were chosen to synthesize a porphyrin‐based COF (TAPBB‐COF) by the solvothermal method. As expected, the valence band (VB) of TAPBB‐COF is thus adjusted to a more suitable position. Additionally, the CO production when using TAPBB‐COF under full‐wavelength light for 12 h was 295.2 μmol g−1, which was three times that of COF‐366, and the new material has good recycling stability and selectivity (95.6 %). Theoretical calculations indicate that the nitrogen of the porphyrin ring and the Schiff base, and the bromine in TAPBB‐COF contribute greatly to the activation of H2O and the conversion of CO2 in the photoreaction.
Tapping into CO2 reduction: 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin (TAPP) and 2,5‐dibromo‐1,4‐benzenedialdehyde were used to synthesize a porphyrin‐based, Br‐modified covalent organic framework (TAPBB‐COF) by the solvothermal method. The valence band of TAPBB‐COF is thus adjusted to a more suitable position, enabling CO production under full‐wavelength light for 12 h to reach 295.2 μmol g−1. Additionally, the new material has good recycling stability and selectivity.
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Dye-sensitized solar cells (DSSCs) are the third generation of photovoltaic cells developed by Grätzel and O'Regan. They have the characteristics of low cost, simple manufacturing process, tunable ...optical properties, and higher photoelectric conversion efficiency (PCE). With an ever increasing energy crisis, there is an urgent need to develop highly efficient, environmentally benign, and energy-saving cell materials. Polyoxometalates (POMs), a kind of molecular inorganic quasi-semiconductor, are promising candidates for use in different parts of DSSCs due to their excellent photosensitivity, redox, and catalytic properties, as well as their relative stability. Following a brief introduction to the development of DSSCs and the potential virtues of POMs in DSSCs, we attempt to make some generalizations about the energy level regulation of POMs that is the underlying theoretical basis for their application in DSSCs, and then we summarize the research progress of POMs in DSSCs in recent years. This is organized in terms of the properties of POMs, namely, electron acceptor, photosensitivity, redox and catalysis, based on the accumulation of our research into POMs over many years. Meanwhile, in view of the fact that the properties of POMs depend primarily on their electronic structural diversity, we keep this point in mind throughout the article with a view to revealing their structure-property relationships. Finally we provide a short summary and remarks on the future outlook. This review may be of interest to synthetic chemists devoted to designing POMs with specific structures, and researchers engaged in the extension of POMs to photoelectric materials.
Polyoxometalate (POM)-based metal-organic framework (MOF) materials contain POM units and generally generate MOF materials with open networks. POM-based MOF materials, which utilize the advantages of ...both POMs and MOFs, have received increasing attention, and much effort has been devoted to their preparation and relevant applications over the past few decades. They have good prospects in catalysis owing to the electronic and physical properties of POMs that are tunable by varying constituent elements. In this review, we present recent developments in porous POM-based MOF materials, including their classification, synthesis strategies, and applications, especially in the field of catalysis.
POM-based MOF materials, which combine the advantages of both POMs and MOFs, have received increasing attention. In this review, we present the recent developments in porous POM-based MOF materials for the first time, including their classification, synthesis strategies and applications, especially in the field of catalysis.
Electrocatalytic reduction of nitrogen (N
2
) is considered as a simple, green, and sustainable method for producing ammonia (NH
3
). Inspired by the recent experimental synthesis of a ...two-dimensional intrinsically conductive Ni-based covalent organic framework (Mirica
et al.
,
J. Am. Chem. Soc.
, 2019,
141
, 11929-11937), here, on the basis of density functional theory (DFT), we explore the electrocatalytic performance of a series of stable and conductive two-dimensional (2D) TM-based covalent organic frameworks (TM-COFs, TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, W, Ir, Pt, and Au, respectively) toward the N
2
reduction reaction (NRR), which are constructed by the robust linkage between 2,3,9,10,16,17,23,24-octaamino-metallophthalocyanine and pyrene-4,5,9,10-tetraone. The computational results show that the 2D conductive Mo-COF exhibits the highest electrocatalytic performance for N
2
fixation with a very low overpotential of 0.16 V among the 20 candidates, and can effectively inhibit the competitive hydrogen evolution reaction (HER). The outstanding NRR activity and selectivity of the Mo-COF stem from its inherent superiorities, such as excellent electrical conductivity, significant positive charge and large spin moment on the Mo atom, and appropriate adsorption strength for NRR species. This work will promote more experimental research in this field to discover more highly active COF-based catalysts for advancing sustainable NH
3
production.
A two-dimensional conductive Mo-COF exhibits excellent electrocatalytic activity for N
2
reduction to NH
3
with an extremely low overpotential (0.16 V), effectively suppressing the competing hydrogen evolution reaction.
With the rapidly growing demand for low‐cost and safe energy storage, the advanced battery concepts have triggered strong interests beyond the state‐of‐the‐art Li‐ion batteries (LIBs). Herein, a ...novel hybrid Li/Na‐ion full battery (HLNIB) composed of the high‐energy and lithium‐free Na3V2(PO4)2O2F (NVPOF) cathode and commercial graphite anode mesophase carbon micro beads is for the first time designed. The assembled HLNIBs exhibit two high working voltage at about 4.05 and 3.69 V with a specific capacity of 112.7 mA h g−1. Its energy density can reach up to 328 W h kg−1 calculated from the total mass of both cathode and anode materials. Moreover, the HLNIBs show outstanding high‐rate capability, long‐term cycle life, and excellent low‐temperature performance. In addition, the reaction kinetics and Li/Na‐insertion/extraction mechanism into/out NVPOF is preliminarily investigated by the galvanostatic intermittent titration technique and ex situ X‐ray diffraction. This work provides a new and profound direction to develop advanced hybrid batteries.
A novel Li/Na‐ion hybrid battery with high working voltage and superior electrochemical and low‐temperature properties is designed and assembled by using lithium‐free Na3V2(PO4)2O2F (NVPOF) and commercial graphite as cathode and anode, respectively. The electrode kinetics and Li/Na‐insertion/extraction processes into/out the NVPOF cathode are preliminarily studied by the galvanostatic intermittent titration technique and ex situ X‐ray diffraction.
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A family of lanthanide-based MOFs (Ln-MOFs) with high thermal and chemical stability have been successfully synthesized by a solvothermal method. Owing to the intrinsic robustness of the framework ...and temperature-dependent luminescence behaviour of lanthanides, Eu3+/Tb3+-mixed MOFs ((CH3)2NH2Eu0.036Tb0.964BPTC) have also been successfully synthesized and targeted for developing excellent luminescent thermometers. The obtained mixed Ln-MOF exhibits ratiometric temperature sensing based on the distinguished characteristic emission of lanthanides with a wide temperature range from 77 K to 377 K. Particularly, the temperature sensor shows good linear responses from 220 K to 310 K with the maximum relative sensitivities (Sm) of 9.42% per K at 310 K. This value is comparable to those of the most excellent Ln-MOF thermometers reported. Besides, the temperature-dependent luminescent colours could also be systematically tuned from green, through yellow to red with increasing temperature, which can be clearly and directly observed even by the naked eye or a camera, thus also allowing colorimetric luminescence thermometry.
Imidazole molecules were frequently incorporated into porous materials to improve their proton conductivity. To investigate how different arrangements of imidazoles in metal–organic frameworks (MOFs) ...affect the overall proton conduction, we designed and prepared a MOF-based model system. It includes an Fe–MOF as the blank, an imidazole@Fe–MOF (Im@Fe–MOF) with physically adsorbed imidazole, and an imidazole–Fe–MOF (Im–Fe–MOF), which contains chemically coordinated imidazole molecules. The parent Fe–MOF, synthesized from the exchange of carboxylates in the preformed Fe3(μ3–O)(carboxylate)6 clusters and multitopic carboxylate ligands, serves as a control. The Im@Fe–MOF was prepared by encapsulating free imidazole molecules into the pores of the Fe–MOF, whereas the Im–Fe–MOF was obtained in situ, in which imidazole ligands coordinate to the metal nodes of the framework. Proton-conductivity analyses revealed that the proton conductivity of Im–Fe–MOF was approximately two orders of magnitude greater than those of Fe–MOF and Im@Fe–MOF at room temperature. The high proton conductivity of 1.21 × 10–2 S cm–1 at 60 °C for Im–Fe–MOF ranks among the highest performing MOFs ever reported. The results of the density functional theory calculations suggest that coordinated imidazole molecules in Im–Fe–MOF provide a greater concentration of protons for proton transportation than do coordinated water molecules in Fe–MOF alone. Besides, Im–Fe–MOF exhibits steadier performance than Im@Fe–MOF does after being washed with water. Our investigation using the above ideal crystalline model system demonstrates that compared to disorderly arranged imidazole molecules in pores, the immobilized imidazole molecules by coordination bonds in the framework are more prone to form proton–conduction pathways and thus perform better and steadier in water-mediated proton conduction.
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Red phosphorus (P) has been recognized as a promising material for lithium/sodium-ion batteries (LIBs/SIBs) because of their high theoretical capacity. However, tremendous volume variation and low ...conductivity limit its widespread applications. Hence, we design and synthesize uniformly distributed honeycomb-like hierarchical micro–mesoporous carbon nanospheres (HHPCNSs) with ultralarge pore volume (3.258 cm3 g–1) on a large scale through a facile way. The large pore volume provides enough space for loading of P and the expansion of P, and the uniform distribution of the micro–mesopores enables the red P to load uniformly. The resulting HHPCNSs/P composite exhibits extremely high capacity (2463.8 and 2367.6 mA h g–1 at 0.1 A g–1 for LIBs and SIBs, respectively), splendid rate performance (842.2 and 831.1 mA h g–1 at 10 A g–1 for LIBs and SIBs, respectively) and superior cycling stability (1201.6 and 938.4 mA h g–1 at 2 and 5 A g–1 after 1000 cycles for LIBs and 1269.4 and 861.8 mA h g–1 at 2 and 5 A g–1 after 1000 cycles for SIBs, respectively). More importantly, when coupled with LiFePO4 and Na3V2(PO4)3 cathode, lithium/sodium-ion full batteries display high capacity and superior rate and cycling performances, revealing the practicability of the HHPCNSs/P composite. The exceptional electrochemical performance is caused by the honeycomb-like carbon network with ultralarge pore volume, uniformly distributed hierarchical micro–mesoporous nanostructure, outstanding electronic conductivity, and excellent nanostructural stability, which is much better than currently reported P/C materials for both LIBs and SIBs.
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