The first example for cycloenantiomeric hexahomooxacali

Cycloenantiomeric hexahomooxacalix[3]arenes with different substituents on the three upper rims were synthesized for the first time by fixing their conformation into a cone. A cycloenantiomeric hexahomooxacalix[3]arene 6 was resolved into both enantiomeric forms and chiroptically characterized. Preliminary 1H-NMR studies indicated that the optically resolved cycloenantiomer 6 could discriminate the enantiomers of hydrochloride of phenylalanine ethyl ester.     

Self-Assembled Nano-Filamentous Zeolite Catalyst to Realize Efficient One-Step Ethanol Synthesis

The non-petroleum synthesis route of ethanol from syngas (H₂+CO) with methyl acetate (MA) as the core intermediate product has been confirmed as an excellent industrialization route for high purity ethanol production. However, as the central part of this tandem-catalysis path, the carbonylation of dimethyl ether (DME) to MA is limited by the undesirable catalytic activity and stability of zeolite catalysts. Herein, a facile inhibitor-assisted strategy was developed for constructing self-assembled nano-Mordenite (nano-MOR) zeolites without using any expensive or complex template. A nano-filamentous MOR zeolite with only 70 nm crystal diameter was successfully synthesized by selectively controlling the crystal growth orientation with a specific inhibitor. The catalytic performance of self-assembled nano-MOR catalysts was remarkably outstanding in DME carbonylation reaction. The highest Space-Time Yield (STY) of MA was achieved over Nanofilament MOR (NF-MOR), which was significantly improved comparing with that of the traditional Ellipsoid-MOR (ES-MOR) [3780 mmol/(kg ⋅ h) vs. 1368 mmol/(kg ⋅ h)]. One-step ethanol synthesis was realized by combining the MOR catalyst and an innovative self-reduced Cu-ZnO/SiO₂ (CZ/SiO₂) catalyst in a rationally designed dual-bed catalysis system. Adopting the tailor-made NF-MOR&CZ/SiO₂ combination, it obtained the highest STY of ethanol, about 4 times of the conventional ES-MOR&CZ combination [1800 mmol/(kg ⋅ h) vs. 476 mmol/(kg ⋅ h)]. The present self-assembled nano-MOR zeolites synthetic strategy opens a new way for the fabrication of high-performance zeolites for practical industrial applications in catalytic conversions of one-carbon (C1) small molecules to high value-added chemicals.     

Alternative simple and effective synthesis of (di)benzoxanthones and their functions toward fluorescent dyes

(Di)benzoxanthones possessing additional benzene units on one or both sides of xanthone were prepared via dehydration of the corresponding dihydroxybenzophenone, where a catalytic amount of K₂CO₃ dramatically increased the yields. Chemical transformations of the versatile carbonyl groups of (di)benzoxanthones could derive fluorescent materials.     

Exhaustive syntheses of naphthofluoresceins and their functions

Naphthofluorescein and/or seminaphthofluorescein derivatives possessing the additional benzene units to one or both sides of fluorescein were exhaustively constructed through Friedel-Crafts type reactions between corresponding aroylbenzoic acids and dihydroxynaphthalenes. Compound 4 works as a one-dye pH indicator, which shows red in strong acid condition and blue in basic solution. Compound 23 (diacetate of compound 4) shows good transitivity to the HEK 293 cells and acts as a fluorescent pigment for the living cell imaging. Compounds 5, 6, and 9 show fluorescent emission in the NIR region (>700 nm) and imply the potentialities of NIR fluorescent probes.     

Synthesis and properties of S,R-alternating octinaphthalenes

(S,R,S,R,S,R,S)- and (S,R,S,S,S,R,S)-octinaphthalenes were synthesized by oxidative coupling of (S,R,S)-quaternaphthalene, and differences due to axis chirality of (S,R,S,R,S,R,S)-, (S,R,S,S,S,R,S)-, (S,S,S,R,S,S,S)-, and (S,S,S,S,S,S,S)-octinaphthalenes were compared using the R_f values on TLC, specific optical rotations, ¹H NMR chemical shifts of the hydroxy groups, and CD spectra. A clear CD additivity was found in the Δ? values of the ¹L_a transition around 290 nm, which are proportional to the difference between the numbers of S and R binaphthalene units.     

Bottom-up synthesis of optically active oligonaphthalenes: three different pathways for controlling axial chirality

The oxidative homocoupling of optically active binaphthalenes 1a-d with a stoichiometric amount of CuCl2 and amines afforded quaternaphthalenes 2a-d in up to 93% de. The high diastereoselectivities were achieved through three different pathways (epimerization of the axis together with diastereoselective crystallization, thermodynamic, and kinetic control pathways). The type of side chains on the naphthalene influenced which pathway dominates. Three pathways were applicable to octinaphthalenes (8a-d) and hexadecanaphthalene 10a with 46-99% de. The absolute configuration of the newly formed axial bond was determined by (1) X-ray crystallographic analysis, (2) transformation to known compounds 15 and 16, (3) CD spectra of oligonaphthalenes with two pyrene rings as exciton parts, and (4) the shift values in 13C NMR spectra of 13C-enriched derivatives 29-31 toward chiral shift reagent Eu(+tfc)3.     

不同改性组分对Cu-ZnO基催化剂低温甲醇合成性能的影响

通过共沉淀法制备了Al、Zr和Ce改性的Cu-ZnO基低温甲醇合成催化剂,采用氮气物理吸附、H2-TPR、CO2-TPD、N2O滴定、XRD和TEM等技术对其进行了表征,并考察了改性组分和煅烧温度对其在170℃下合成气制甲醇催化性能的影响。结果表明,经Zr改性的Cu-ZnO基催化剂,其低温甲醇合成性能较好;随着煅烧温度的降低,Cu在催化剂表面的分散度逐渐变大、颗粒逐渐变小,所得到的催化剂其活性也较高;其中,未经煅烧的Cu-ZnO/ZrO2催化剂的活性最佳,其甲醇时空产率为106.02 g/(kg·h),选择性达87.04%。     

Effect of supercritical fluid of CO2 drying during Cu/ZnO catalyst preparation on methanol synthesis from syngas at low temperature

A copper-based catalyst can be utilized to synthesize methanol from syngas containing carbon dioxide as well as water at low temperature and low pressure. However, the agglomeration of the metallic copper and zinc oxide decreased the catalyst surface area and the Cu-specific surface area. In order to prevent the sintering, the supercritical CO₂ was used to extract water from the catalyst precursor. Our results demonstrate that the Cu-specific surface area was the essential factor to affect the catalytic activity. A larger Cu-specific surface area would cause higher methanol synthesis activity. The optimized supercritical CO₂ drying condition was at 308?K and 8.0?MPa for 3?h when the methanol yield reached 44.8%.     

Linear and nonlinear transports of coupled quantum dots

Series of double quantum dots each with a size around 400 × 400nm² have been realized by delineating a 2DEG in modulation-doped AlGaAs/GaAs with 100 nm wide Schottky split gates fabricated by an electron-beam lithography and a lift-off technique. The split gate in the middle of the double dot allows us to control interdot coupling widely. The charging diagram obtained from linear transports in the Coulomb blockade regime shows that the isolated dots merge into a single composite dot with increase of interdot coupling. A clear Coulomb staircase has been observed in the double-dot system at a limited high-bias condition.     

Direct and Oriented Conversion of CO2 into Value-Added Aromatics

The oriented conversion of CO₂ into target high-value chemicals is an effective way to reduce carbon emissions, but still presents a challenge. In this communication, we report the oriented conversion of CO₂ into value-added aromatics, especially para-xylene, in a single pass by combining core–shell structured Zn-doped H-ZSM-5 (Zn-ZSM-5@SiO₂) and a Cr₂O₃ component. Through precise regulation of the acidity of Zn-ZSM-5@SiO₂, high para-xylene selectivity (38.7 % in the total products) at a CO₂ conversion of 22.1 % was achieved. Furthermore, a CO₂-assisted effect in the synthesis of aromatics during the tandem process has been clarified through a control experiment. The CO₂ reactant can act as a hydrogen acceptor to accelerate the dehydrogenation of alkenes, intermediates in the synthesis of aromatics, thereby increasing the driving force towards aromatics in the tandem reaction process.