Asymmetric photocatalysis over robust covalent organic frameworks with tetrahydroquinoline linkage

The asymmetric photocatalytic organic synthesis(APOS)process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source.However,it still lacks efficient semiconductors with tunable band structures and has a low recycling stability.Herein,we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks(QH-COFs)with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetricα-alkylation of aldehydes by merging with a chiral secondary amine.Up to 94%ee was obtained over QH-COFs,and the activity of QH-COFs was significantly higher than those of inorganic semiconductors(e.g.,Ti O2,Bi VO4,and WO3)under similar conditions,which is mainly attributed to their narrow band gap and suitable band edge.As far as we know,QH-COFs are the most active semiconductors for asymmetricα-alkylation of aldehydes ever reported.The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts.Attributed to the tetrahydroquinoline linkage,QH-COFs showed extremely high recycling stability,which made practicals application possible.This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.

Development of efficient solid chiral catalysts with designable linkage for asymmetric transfer hydrogenation of quinoline derivatives

Developing chiral solid catalysts for asymmetric catalysis is desirable for the elimination of homogeneous catalysis flaws but remains an immense challenge.Herein,we report the immobilization of TsDPEN on SBA‐15 with an ionic liquid(IL)linkage via the one‐pot reaction of imidazole‐TsDPEN‐N‐Boc with 3‐(trimethoxysilyl)propyl bromide in the SBA‐15 mesopores.After coordination to Rh,the chiral solid catalysts could efficiently catalyze quinoline transfer hydrogenation,achieving 97%conversion with 93%ee,which was comparable to their homogeneous counterparts.The chiral solid catalyst with the IL linkage afforded much higher turnover frequency than that without the IL linkage(93 h^(–1)vs.33 h^(–1)),attributed to the phase transfer and formate‐enriching ability of the IL linkage.Furthermore,the effect of the pH on the reaction rate of the solid catalyst was investigated,preventing reaction rate retardation during the catalytic process.The tuning of the linkage group is an efficient approach for catalytic activity improvement of immobilized chiral catalysts.

Co NP/NC hollow nanoparticles derived from yolk-shell structured ZIFs@polydopamine as bifunctional electrocatalysts for water oxidation and oxygen reduction reactions

The pyrolysis under inert atmosphere has been widely used for the synthesis of metal containing heteroatoms doped carbon materials, versatile catalysts for various reactions. However, it is difficult to prevent metal nanoparticles aggregation during pyrolysis process. Herein, we reported the efficient synthesis of nitrogen doped carbon hollow nanospheres with cobalt nanoparticles （Co NP, ca. 10nm in size） distributed uniformly in the shell via pyrolysis of yolk-shell structured Zn-Co-ZIFs@polydopamine （PDA）. PDA acted as both protection layer and carbon source, which successfully prevented the aggregation of cobalt nanoparticles during high-temperature pyrolysis process. The Co NP and N containing carbon （Co NP/NC） hollow nanospheres were active for both oxygen evolution reaction （OER） and oxygen reduction reaction （ORR）, affording overpotential of 430 mV at 10 mA/cm2 for OER in 1 M KOH and comparable half-wave potential to that of Pt/C （0.80V vs RHE） for ORR in 0.1 M KOH. The superior performance of carbon hollow nanospheres for both OER and ORR was mainly attributed to its small metal nanoparticles, N-doping and hollow nanostructure. The protection and confinement effect that originated from PDA coating strategy could be extended to the synthesis of other hollow structured carbon materials, especially the ones with small metal nanoparticles.

One-pot synthesis of mesosilica/nano covalent organic polymer composites and their synergistic effect in photocatalysis

Organic-inorganic hybrid materials provide a desirable platform for the development of novel functional materials.Here,we report the one-pot synthesis of mesoporous hybrid nanospheres by the in-situ sol-gel condensation of tetraethoxysilane around surfactant micelle-confined nano covalent organic polymer(nanoCOP)colloids.The hybrid nanospheres containing nanoCOPs uniformly distributed in the mesosilica network,inherited the visible light responsive properties of the nanoCOPs.The turnover frequency of the hybrid nanospheres is almost 12 times that of its corresponding bulk COP counterpart for the photocatalytic reductive dehalogenation of a-bromoacetophenone,which is attributed to activation of the Hantzsch ester reductant by the hydroxyl group.The existence of a volcano relationship between the activity and nano COP/mesosilica ratio confirmed the synergistic effect between nano COP and mesosilica.Our preliminary results suggest that hybridization of semiconductors and reactant-activating materials is an efficient strategy for enhancing the activity of a catalyst for photocatalysis.

Synthesis of polymer/CNTs composites for the heterogeneous asymmetric hydrogenation of quinolines

The development of heterogeneous catalytic processes is crucial for the synthesis of chiral compounds for both academic and industrial applications.However,thus far,such achievements have remained elusive.Herein,we report the heterogeneous asymmetric hydrogenation of 2-methylquinoline over solid chiral catalysts,which were prepared by the one-pot polymerization of(1R,2R)-N-(4-vinyl-benzenesulfonyl)-1,2-diphenylethane-1,2-diamine(VDPEN)and divinylbenzene(DVB)in the presence or absence of activated carbon(C)or carbon nanotubes(CNTs),followed by Ru coordination and anion exchange.The solid chiral catalysts were fully characterized by N2 sorption analysis,elemental analysis,TEM,FT-IR spectroscopy,and 13C CP-MAS NMR.All the solid chiral catalysts could efficiently catalyze the asymmetric hydrogenation of 2-methylquinoline to afford 2-methyl-1,2,3,4-tetrahydroquinoline with 90%ee.Studies have shown that polymer/C and polymer/CNTs composites are more active than pure polymers.The polymer/CNTs composite exhibited the highest activity among all the solid chiral catalysts under identical conditions,owing to the unique morphology of CNTs.The recycling stabilities of the solid chiral catalysts were greatly improved when ionic liquids(ILs)were employed as solvents;this is mainly attributed to the decreased leaching amount of anions owing to the confinement effect of ILs on ionic compounds.

In vivo comparison of transduction efficiency with recombinant adenovirus-mediated p53 in a human colon cancer mouse model by different delivery routes

Objective： To evaluate transduction efficiency with recombinant adenovirus-mediated p53 （rAd/p53） therapy in a human colon cancer mouse model by intra-tumoral injection and intra-arterial delivery. Methods： The tumor pieces of human colon cancer SW480 were implanted in the livers of 45 nude mice. These mice were administrated with rAd/p53 by intratumoral injection and intra-artedal delivery. After 24 h, 48 h and 72 h tAd/p53 administration, 5 mice each group were killed with over anesthesia and their livers were removed. P53 expression and apoptosis of tumor and liver were assessed. Results： P53 expression and apoptosis of intratumoral administration group was higher than tail vein group and control group. Apoptosis and p53 expression of livers in three groups had no significant difference. Conclusion： p53 gene transducUon efficiency and anticancer effect of rAd/p53 is much better by intra-tumoral injection than intra-arterial delivery,

Recent progress in photocatalytic NAD(P)H regeneration for photocatalytic-enzymatic-coupling system

The enzymatic redox reactions in natural photosynthesis rely much on the participation of cofactors,with reduced nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate(NADH/NADPH)or their oxidized form(NAD+/NADP+)as an important redox power.The photocatalytic regeneration of expensive and unstable NADH/NADPH in vitro is an important process in enzymatic reduction and has attracted much research attention.Though different types of photocatalysts have been developed for photocatalytic NADH/NADPH regeneration,the efficiency is still relatively low.To elucidate the key factors affecting the performance of photocatalytic NADH/NADPH regeneration is helpful to rationally design the photocatalyst and improve the photocatalytic efficiency.In this paper,we overview the recent progress in photocatalytic NADH/NADPH regeneration with the focus on the strategies to improve the visible light adsorption,the charge separation and migration efficiency,as well as the surface reaction,which jointly determine the overall photocatalytic regeneration efficiency.The potential development of photocatalytic NADH/NADPH regeneration and photocatalyticenzymatic-coupling system is prospected finally.

Transparent perovskite glass-ceramics for visual optical thermometry

Optical thermometers have aroused considerable attention in recent years,and the increasing demand of sensitivity for practical application encourages the investigation on developing innovative non-contact optical thermo metric materials with higher sensitivity and accuracy.Perovskite quantum dots(QDs)with excellent temperature-dependence optical properties,provide a feasible approach to realizing the detection of temperature change,however,their poor high temperature thermal stability and the facile realization to obtain the production remain a daunting challenge.Herein,growing Tb^(3+)-doped CsPbl_(3) QDs in situ in borosilicate glass is proposed,which ensures the phase stability,and high-efficiency florescence output of the all-inorganic perovskite as a temperature sensor.A higher absolute and relative temperature sensitivity(0.0398 K^(-1) and 7.12%/K,respectively),along with the visible color change from orange-red to yellow-green with the increase of temperature is accomplished.Notably,the repeatable florescence intensity of Tb^(3+)-doped CsPbl_(3) QDs under high temperature enables their temperature sensing application.

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

Enhancing the charge separation efficiency is highly effective strategy in improving the photocatalytic activity of covalent organic frameworks(COFs)which have the problems of low conductivity and difficult dissociation of excitons.In this work,we report the sevenfold increase in apparent quantum efficiency resulting from the use of a near-single layer COF(SLCOF)in photocatalytic hydrogen evolution compared with bulk COF.Detected by transient absorption spectroscopy characterization,100% of photogenerated long-lived electrons in the near-SLCOF can be extracted and participate in the photocatalytic process.However,the electron extraction efficiency declined to only about 11% when the COFs were increased to eight layers,implying the difficulty of charge migration among COFs interlayers.The near-SLCOF was prepared by deposition of selfexfoliated COFs colloids on SiO_(2),driven by their strong affinity.This work not only sheds light on the significant influence of COF layer thickness on the charge separation efficiency but also provides a new route to prepare and stabilize COF layers for practical applications.

Fabrication of ZnO with tunable morphology through a facile treatment of Zn-based coordination polymers

The morphology and structure of zinc oxide(ZnO), one of the important semiconductors, are relevant to its properties and applications. The preparation of ZnO with tunable morphology and desired structure is an attractive topic in the field of material synthesis. This work reports a facile method for the synthesis of Zn O with controllable morphology and crystal orientation using Zn-based coordination polymer particles(Zn-CPP) as precursors. Using hydrothermal method, Zn-CPP with morphologies of microrod, nanoplate, flower-like, arrow-tipped microsheet, and square cylinder were successfully synthesized via the coordination between metal ions Zn2+ and organic ligand 1,4,5,8-naphthalenetetracarboxylic dianhydride in aqueous solution. Subsequent thermal treatment of the Zn-CPP successfully resulted in the formation of porous Zn O with similar morphology to Zn-CPP. It is also found that the Zn O with enhanced(002) orientation could be obtained from Zn-CPP with preferred(002) orientation. This strategy could be extended for the preparation of other metal oxides with desired shape and structure.