Latest ArticlesThe series of heterodinuclear metal oxide carbonyls in the form of TaNiO(CO) n- (n = 5–8) are generated in the pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy. During the consecutive CO adsorption, the μ2-O-bent structure initially is the most favorable for TaNiO(CO)5-, and subsequently both μ2-O-bent and μ2-O-linear structures are degenerate for TaNiO(CO)6-, then the μ2-O-linear structure is most preferential for TaNiO(CO)7-, and finally the η2-CO2-tagged structure is the most energetically competitive one for TaNiO(CO)8-, i.e., the CO oxidation occurs at n = 8. In contrast to the literature reported CO oxidation on heteronuclear metal oxide complexes generally proceeding via Langmuir–Hinshelwood-like mechanism, complementary theoretical calculations suggest that both Langmuir–Hinshelwood-like and Eley–Rideal-like mechanisms prevail for the CO oxidation reaction on TaNiO(CO)8- complex. Our findings provide new insight into the composition-selective mechanism of CO oxidation on heteronuclear metal complexes, of which the composition be tailored to fulfill the desired chemical behaviors.
An efficient, sustainable and scalable strategy for the synthesis of porous cobalt/nitrogen co-doped carbons (Co@NCs) via pyrolysis of aniline-modified ZIFs, has been demonstrated. Aniline can coordinate and absorb on the surface of ZIF (ZIF-CoZn3-PhA), accelerate the precipitation of ZIFs, thus resulting in smaller ZIF particle size. Meanwhile, the aniline on the surface of ZIF-CoZn3-PhA promotes the formation of the protective carbon shell and smaller Co nanoparticles, and increases nitrogen content of the catalyst. Because of these properties of Co@NC-PhA-3, the oxidative esterification of 5-hydroxyme-thylfurfural can be carried out under ambient conditions. According to our experimental and computational results, a synergistic catalytic effect between CoNx sites and Co nanoparticles has been established, in which both Co nanoparticles and CoNx can activate O2 while Co nanoparticles bind and oxidize HMF. Moreover, the formation and release of active oxygen species in CoNx sites are reinforced by the electronic interaction between Co nanoparticles and CoNx.
Reliable technologies for CO2 capture and conversion (C3) are of vital importance for the establishment of a sustainable society. Metal-organic framework (MOF) composites have shown their compelling potentials for C3 due to the plentiful reticular chemistry of MOF structures and the synergistic catalysis between MOFs and the functional guests. This review focuses on the syntheses and catalytic applications towards C3 of MOF composites, which is divided into three sections. The first section gives a brief introduction about synthetic strategies of MOF composites. The second section discusses the recent progress of MOF composites in C3, including CO2 chemical fixation, hydrogenation, photoreduction, electroreduction and photoelectroreduction. The third section summarizes the challenges and future prospects of MOF composites for C3. We hope that this review cannot only provide an inspiration for the rational design of MOF composites for C3, but also stimulate more and more research works in this emerging area.
Transition metal-catalyzed carbene transfer reaction is one of the most notable advances for C−C bond formation reactionsduring the past decade, which has been widely employed in the preparation of C3-substituted indoles. Here, we described an efficient example of catalyst- and metal-free aminoboration of alkynes and C−C bond formation with diazo compounds to produce C3-substituted indoles. Diverse alkynylanilines and diazo compounds can be utilized for this tandem transformation under mild reaction conditions, resulting in broad functional group compatibility. Additionally, this metal-free strategy can be extended to construct substituted benzofurans.
The effect of cucurbit[7]uril (CB[7]) on fluorescence properties and biocompatibility of the bis-viologen biphenyl molecule (BPV22+) was investigated by using 1H NMR spectroscopy, fluorescence emission titration, and in vitro cytotoxicity experiments. CB[7] can be combined with BPV22+ in a stoichiometric ratio of 1:1 and 2:1. After the formation of host-guest complex, the fluorescence emission intensity of BPV22+ increased significantly, and the emission spectrum blue shifted. Meanwhile, the host-guest complexes showed better biocompatibility than BPV22+ in cell cytotoxicity studies. Results of this paper lay a foundation for the development of host-guest type of fluorescent probes, biological imaging and so forth.
Long-emission carbon dots (CDs) is triggering immense enthusiasm on account of their intrinsic merits of high chemical stability and excellent optical properties. In this study, a facile and rapid approach was developed for the preparation of barium-doped carbon dots (Ba-CDs) with yellow fluorescence emission and high quantum yields. Surface chemistry and the chemical architecture of the Ba-CDs was revealed under various spectroscopic methods. This work provides more insights into the effects of charge transfer caused by Ba heteroatoms, which is considered as the most challenging step in the investigation on luminescence mechanism. Remarkably, the prepared Ba-CDs were successfully applied as fluorescent probes in the detection of trace water in organic solvents (ethanol, isopropanol, acetone, tetrahydrofuran). Comparing with traditional fluorescent probes for water detection in organic solvents, Ba-CDs detection provides a more sensitive, much faster and more economical approach.
Three new emitters, namely 10, 10'-(quinoline-2, 8-diyl)bis(10H-phenoxazine) (Fene), 10, 10'-(quinoline-2, 8-diyl)bis(10H-phenothiazine) (Fens) and 10, 10'-(quinoline-2, 8-diyl)bis(9, 9-dimethyl-9, 10-dihydroacridine) (Yad), featuring quinoline as a new electron acceptor have been designed and conveniently synthesized. These emitters possessed small singlet–triplet splitting energy (ΔEst) and twisted structures, which not only endowed them show thermally activated delayed fluorescence (TADF) properties but also afforded a remarkable aggregation-induced emission (AIE) feature. Moreover, they also showed aggregation-induced delayed fluorescence (AIDF) property and good photoluminescence (PL) property, which are the ideal emitters for non-doped organic light-emitting diodes (OLEDs). Furthermore, high-performance non-doped OLEDs based on Fene, Fens and Yad were achieved, and excellent maximum external quantum efficiencies (EQEmax) of 14.9%, 13.1% and 17.4%, respectively, were obtained. It was also found that all devices exhibited relatively low turn-on voltages ranging from 3.0 V to 3.2 V probably due to their twisted conformation and the AIDF properties. These results demonstrated the quinoline-based emitters could have a promising application in non-doped OLEDs.
In many reactions involving selenosulfonate or thiosulfonate, the sulfone group often leaves in form of benzenesulfinic acid or sodium benzenesulfinate. A one-pot two-step reaction of selenosulfonate with isocyanides and allyl alcohol under aqueous conditions to afford selenocarbamates and allyl sulfone compounds is reported. The sulfinic acid as the first-step side product is converted to the allyl sulfone compound by water promoted reaction with allyl alcohol. Water acts as both an oxygen source of selenocarbamates and as a promoter to drive the second step reaction. The reactions have the advantages of mild conditions, green, environment-friendly, and high atomic economy.
Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent (TADF) emitters (namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via CN coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core. It is found that, compared with the commonly-used tert-butyl groups, the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers, producing stronger TADF effect together with faster reverse intersystem crossing process. Solution-processed TADF organic light-emitting diodes (OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%, respectively, which are ~1.6 and ~2.0 times that of the tert-butyl-encapsulated counterparts. These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.
Specific topographic Ni anchoring on reduced graphene oxide (rGO) composites show an astronomical potential as effective wave absorbers due to the synergistic electromagnetic loss effects. Herein, Ni/rGO composites with different topography were successfully prepared via hydrothermal in-situ reduction method. The structure and morphology characteristics revealed that particle-like, chain-like, coin-like and flower-like Ni were closely anchored onto rGO, respectively. The electromagnetic wave absorption (EMA) performance revealed that chain-like Ni/rGO exhibited the optimal reflection loss of -43.7 dB with a thickness of 1.8 mm as well as the EAB of 6.1 GHz at 2.0 mm among all samples due to the good impedance match and the synergistic dielectric and magnetic losses. Besides, one conclusion can be drawn that excellent magnetic coupling effect and impedance matching were the main reasons for significantly improving the EMA performance. Considering the systematic dependence of morphology on EMA, this work provides a perspective for designing high-performance absorbing materials.
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