Latest ArticlesAn array of pyridine-ester enolate based organoboron complexes has been designed and synthesized via a one-pot cascade of Pd-catalyzed α-arylation and BF2 complexation. The rapid structure-activity relationship (SAR) studies indicated that unsymmetrical N,O-chelated BF2 complexes were highly fluorescent in solid state, and exhibited large Stokes shifts, excellent photostability, along with insensitivity to pH. The α-aryl group could not only modulate the electronic effect but also inhibit the intermolecular π-π stacking to promote the aggregation-induced emission (AIE) effect. DFT calculations and experiments identified that the intramolecular charge transfer properties of these N,O-chelates could be switched by the modification of substituents, resulting tunable fluorescence wavelengths. Furthermore, post-complexation modification was accomplished, including Suzuki-Miyaura cross-coupling, Buchwald-Hartwig amination, oxidative cleavage, along with a unique triple substitution reaction involving propargyl Grignard reagents. The exemplificative application of dimethylamine substituted boron complex as a reversible acidic vapor sensor was also demonstrated.
The purification of low-grade coal-bed methane is extremely important, but challenging, due to the very similar physical properties of CH4 and N2. Herein, we proposed a dual polarization strategy by employing triazine and polyfluoride sites to construct polar pores in COF materials, achieving the efficient separation of CH4 from N2. As expected, the dual polarized F-CTF-1 and F-CTF-2 exhibit higher CH4 adsorption capacity and CH4/N2 selectivity than CTF-1 and CTF-2, respectively. Especially, the CH4 uptake capacity and CH4/N2 selectivity of F-CTF-2 is 1.76 and 1.42 times than that of CTF-2. This work not only developed promising COF materials for CH4/N2 separation, but also provided important guidance for the separation of other adsorbates with similar properties.
The selective oxidative esterification of aldehydes with alcohols to the corresponding esters has been one of the hot spots in scientific research and industrial synthesis. However, the application of precious metal catalytic systems is limited by their complicated synthetic steps and high cost. Thus a highly efficient, green, recyclable selective synthesis method of esters catalyzed by polyoxovanadate (POV)-based molecular catalysts has been developed in this paper. The results show that supramolecular interaction between POV and 1,3-dibenzylimidazolium bromide (Act2Im) can efficiently convert alcohols and aldehydes to the corresponding esters in high yield under much milder conditions. Mechanistic insight is also provided based on the control experiments, single crystal X-ray diffraction and cyclic voltammetry studies.
Concise chemistry leads to a family of heptanuclear CoⅡ-clusters, [Co7(N3)12(CH3CN)12] [Y2(NO3)4(piv)4]·2CH3CN (DC1) (pivH = pivalic acid), [Co7(N3)12(CH3CN)10(NO3)0.4 (Cl)1.6]·4CH3CN (DC2) and [Co7(N3)12(CH3CN)10(NO3)2]·4CH3CN (DC3), in which the metal ions are exclusively bridged by end-on azido ligands to stabilize a beautiful disk-like topology. The resulting clusters exhibit interesting structural transformations and thermodynamically-distinct steady states verified by theoretical calculations. Magnetic studies reveal the first observation of zero-field SMM behaviour in disk-like heptanuclear CoⅡ complexes.
Metal-organic frameworks (MOFs) functionalized with open metal sites (OMSs) have received widespread attention in various applications due to their fascinating electronic properties and unique interactions with guest molecules. However, rational tailoring of the coordination environment of metal nodes during the synthesis of MOFs remains a great challenge due to their tendency of saturated coordination with linkers. Herein, we reported the construction of three new MOFs featuring unsaturated Cu(Ⅱ) sites, namely [Cu(HCOO)(pzta)]n (HL-1), {[Cu(PTA)0.5(pzta)(H2O)]·2H2O}n (HL-2) and [Cu(NA)0.5(pzta)]n (HL-3) (Hpzta = 3-pyrazinyl-1,2,4-triazole; PTA = terephthalic acid; NA = 1,4-naphthalene dicarboxylic acid), based on the mixed-linker strategy via specific selection of versatile Hpzta ligand and carboxylate ligands. Remarkably, the obtained MOFs exhibited excellent activity and good recyclability for the catalytic reduction of nitroaromatics under mild conditions (25 ℃ and 1 atm). In particular, the complete conversion of 4-nitrophenol (4-NP) took only 30 s on HL-2, reaching a record-high TOF value compared with previously reported metal catalysts. The combined experimental and theoretical studies on HL-2 revealed that the open Cu site with positive-charged nature could improve the adsorption and subsequent electron transport between the substrates, and was responsible for the outstanding performance. This work shined lights on the further enhancement of performance for MOFs through rational OMSs construction.
Electron-deficient viologens are widely used as ligands or structure-directing agents (SDAs) to synthesize crystalline X-ray induced photochromic materials. Here, a new rational strategy of anion-directed folding a flexible cation (H2imb)2+ ((H2imb)2+ = di-protonated 2,3-bis(imidazolin-2-yl)-2,3-dimethylbutane) has been developed. Electron-donating Cl− and (ZnCl4)2− are used to direct folding a flexible electron-deficient (H2imb)2+ cation. Three complexes (H2imb)(NO3)2 (1), (H2imb)Cl2·H2O (2), and (H2imb)ZnCl4 (3) have been synthesized in which (H2imb)2+ crystallize in an anti-conformation, 88.8°-gauche, and 51.8°-gauche, respectively. In contrary to X-ray silent complex 1, X-ray induced photochromism has been achieved in both complex 2 and 3. An intermolecular charge-transfer mechanism has been elucidated and the anion directed folding of (H2imb)2+ has been validated to be critical to yield colored long-lived charge-separated states.
The widespread application of phenolic substances in the field of food, medicine and industry, is harmful to the environment and human health. Therefore, it is very important to develop a convenient and effective method to detect and degrade phenolic compounds. Herein, we report a new keggin-type polyoxometallate-based metal-organic complex self-assembled under solvothermal condition, {[Cu(dap)(3-PA)]4(SiW12O40)(H2O)2}·2H2O (1, dap = 1,2-diaminopropane, 3-HPA = 3-pyridineacrylic acid). 1 shows an interesting 1D ladder-like structure. As a bifunctional catalyst, 1 can be employed as a colorimetric sensor toward phenol with the relatively low detection limit (LOD) of 0.36 µmol/L (S/N = 3) in the wide range (0.001–0.1 mmol/L). The title colorimetric sensor is applied to determine phenol in various water environment with good recoveries ranging from 95%–105%. In addition, 1 also exhibits excellent photocatalytic degradation toward phenol under visible light with the highest removal efficiency at 96% for 100 min and wide pH universality. The selectivity, stability and reliability of the detection of 1 towards phenol, as well as the detection for 4-chlorophenol, o-cresol, 4-nitrophenol and phloroglucinol were studied. Furthermore, the photocatalytic reaction kinetics and the mechanisms of photodegradation of phenol were also investigated in detail.
Focused on the performance promotion of organic small molecular dyes based photothermal agents via non-chemical modification, we found that heat-assisted binding of human serum albumin (HSA) to the dye causes shrinkage of the protein and encapsulate the dye to form nanoparticles. This revolutionizes the photostability of small molecule dyes which further improves their photothermal conversion efficiency and tumor ablation performance as photothermal agents significantly. In this work, the obtained photothermal agent named HSA-P2-T could accumulate in tumor and induce 22 ℃ enhancement of the tumor in xenograft models upon ultra-low dose (0.1 W/cm2) laser irradiation, which, as far as we know, is the lowest laser dose used in vivo photothermal therapy. Utilizing HSA-P2-T, we realized tumor ablation upon twice intravenous injections of the nanoparticles and four photothermal treatments.
In the development of 3D conductive frameworks for lithium metal anode (LMA), two models have been proposed: top growth model and bottom-up growth model. However, Li tends to accumulate on the top of these 3D frameworks with homogenous lithiophilicity (top growth) and Li dendrite still forms. To address this issue, some researchers have focused on developing 3D frameworks with gradient lithiophilicity, which realized bottom-up growth of Li. Nevertheless, partial Li nucleation sites on the top of these frameworks were missed. Inspired by the two models talked above, this work firstly proposed a novel intermittent lithiophilic model for lithium deposition. To demonstrate the feasibility of this model, a bimetallic metal-organic frameworks derived ZnMn2O4-MnO nanoparticles were grown on carbon cloth for LMA. It can cycle stably under ultra-high current and areal capacity (10 mA/cm2, 10 mAh/cm2). The in-situ optical microscopy (OM) was conducted to observe the Li deposition behavior, no dendrite was found during 80 h in ester-based electrolyte while the pure Li only cycled for 2 h. What is more, it can also be well-coupled with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and solid-state electrolyte, which further prove the advantages of the intermittent model for the development of LMAs with high safety and high energy density.
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