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Rational design of pre-catalysts to in situ form active structures is vital for efficient catalysis, especially when surface reconstruction occurs. Here we report a surface engineering strategy to form highly active surfaces on Ni-based catalysts (NiMo in this work) under oxygen evolution reaction (OER) conditions. The NiMo catalyst is decorated with mononuclear Fe–O5 species on its surface. During the OER reconstruction process, the Fe–O5 species will further bond to the surface of Ni oxyhydroxide reconstructed from NiMo. In situ X-ray absorption spectroscopy and theoretical calculations reveal that the Fe–O5 species anchored on Ni oxyhydroxide are easily oxidized under OER conditions, which compensates for the charges of Ni and increases the reducibility of Ni active sites. As a result, such a catalyst shows a 33-fold increase in intrinsic activity compared with the NiMo catalyst, which also decreases the full cell voltage by 0.72 V at 500 mA cm−2 in an anion exchange membrane electrolyzer compared with the IrO2 catalyst. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs), featuring semiconductor-like behavior, have recently garnered widespread interest for applications in photocatalysis by virtue of their well-defined and tailorable porous structures, high surface areas and excellent chemical stability. A facile strategy for designing COFs exerting efficient charge transfer and separation as well as suppressing charge carrier recombination is the precise integration of electron-donating and electron-withdrawing moieties to form long-range ordered donor–acceptor (D–A) type structures. In this work, we rationally designed and synthesized a novel imine-linked COF (DABT-Py-COF) by the condensation of a newly designed D–A–D type monomer of 4,4′,4′′,4′′′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(9,9-dimethyl-9,10-dihydroacridine-10,2,7-triyl))tetrabenzaldehyde and 1,3,6,8-tetrakis(4-aminophenyl)pyrene under solvothermal conditions. Remarkably, the obtained DABT-Py-COF exhibited outstanding and steady hydrogen production with a maximum hydrogen evolution rate (HER) of 5458 μmol g−1 h−1 under visible-light irradiation (AM 1.5). This work has paved the way for the rational design and preparation of more efficient D–A type COFs for photocatalysis. [ABSTRACT FROM AUTHOR]

A fully sp2-carbon conjugated COF (Py-FTP-COF) was designed and synthesized, exhibiting excellent hydrogen evolution rate of 5.22 mmol g−1 h−1. More importantly, in situ hydrogenation of nitroarenes under visible-light irradiation without any additional hydrogen source was successfully accomplished for the first time over COF-based materials. [ABSTRACT FROM AUTHOR]

Metal oxide sensors face the challenge of high response and fast recovery at low operating temperatures for the detection of toxic and flammable hydrogen sulfide (H2S) gases. Herein, novel In-doped ZnO with a sunflower-like structure and tunable surface properties was rationally synthesized. The substitutional In atom in the ZnO crystal can dramatically enhance the concentration of oxygen vacancies (Ov), the In–ZnO sites are responsible for fast recovery, and the formation of sub-stable sulfide intermediates gives rise to the high response towards H2S. As a result, the response of the optimized 4In–ZnO sensor is 3538.36 to 50 ppm H2S at a low operating temperature of 110 °C, which is 106 times higher than that of pristine ZnO. Moreover, the response time and recovery time to 50 ppm H2S are 100 s and 27 s, respectively, with high selectivity and stability. First-principles calculations revealed that 4In–ZnO with rich Ov exhibited higher adsorption energy for the H2S molecule than pristine ZnO, resulting in effortless H2S detection. Our work lays the foundation for the rational design of highly sensitive gas sensors through precise doping of atoms in oxygen-rich vacancies in semiconductor materials. [ABSTRACT FROM AUTHOR]

The detection of volatile organic gas triethylamine (TEA) is of great significance to environment quality and human health. However, it is still a challenge to achieve high-sensitivity detection at low temperatures. In this work, a TEA sensor with a low operating temperature and high response was successfully prepared by designing ZnO/SnO2 composite material rich in oxygen vacancy defects. A camellia-like ZnO material was synthesized by a hydrothermal method using surfactant, bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) as a soft template. SnO2 nanoparticles with a diameter of 20 nm were dispersed on ZnO nanosheets to form a ZnO/SnO2 heterostructure. The sensor based on ZnO/SnO2-10 demonstrates an extremely high response of 780 to 100 ppm TEA. More importantly, the response value of 1 ppm TEA detected is 6 and the detection limit is as low as 0.43 ppm. Besides, the sensor has a low working temperature of 100 °C. The enhancement of TEA sensing performance could be attributed to the synergistic effect of oxygen vacancy (Vo), ZnO–SnO2 heterojunction, and the ZnO (001) exposure plane. Vo can be used as the active center of oxygen molecule adsorption to produce highly active O2− species. Furthermore, Vo–ZnO has higher adsorption energy for TEA molecules than pure ZnO, which was determined using first-principles calculations, confirming the strong interaction between Vo–ZnO and TEA. The sensor shows a broad application prospect in food safety detection and environmental monitoring. [ABSTRACT FROM AUTHOR]

A benzodifuran-based donor–acceptor covalent organic framework was synthesized and employed for efficient simulated sunlight-driven photocatalytic hydrogen evolution from water, which exhibited a superior and steady hydrogen evolution rate of 1390 μmol g−1 h−1 and an outstanding apparent quantum yield (AQY) of 7.8% was obtained at 420 nm. [ABSTRACT FROM AUTHOR]

Restacking of 2D nanomaterials is often deemed to be detrimental to their applications. In contrast to this common notion, here we demonstrate that tightly packed stacked MoS2 exhibits a higher electrocatalytic activity for hydrogen evolution than the more loosely stacked ones. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs), as a new emerging class of highly crystalline advanced porous materials with fascinating structural tunability and diversity as well as the desired semiconductor properties, have gained significant attention as highly promising and efficient photocatalysts or designer platforms for a variety of photocatalytic applications in recent years; thus a comprehensive review is timely to summarize the advances of this field. In this review, a background and brief timeline concerning the developments and key achievements of COFs are provided. Afterwards, a systematic overview of the potential photocatalytic applications realized to date in the fast growing field of COFs is provided with the aim of presenting a full blueprint of COFs for possible photochemical energy conversion and reactions. Finally, the challenges remaining and personal perspectives on further development of this type of material for photocatalysis are presented. [ABSTRACT FROM AUTHOR]

Many highly active electrocatalysts for the reduction of N2 to NH3 (NRR) have been synthesized but suffer from poor selectivity. One crucial reason is that the adsorption of hydrogen often dominates at the active centers at applied voltage, which leads to the competitive hydrogen evolution reaction. This work used density functional theory (DFT) calculations to develop a class of stable polyoxometalate-based electrocatalysts including phosphomolybdic-, phosphotungstic-, silicotungstic-, and silicomolybdic-acid supported Ru single atoms to efficiently catalyze the NRR process with an overpotential lower than 0.25 V. More importantly, phosphomolybdic- and phosphotungstic acid-supported Ru electrocatalysts can achieve high selectivity at applied voltage. This work offers useful insights into designing high-performance polyoxometalate-based electrocatalysts for the NRR. [ABSTRACT FROM AUTHOR]

An efficient enantioselective dearomatization of 2-nitrobenzofurans was realized via an organocatalyzed one-step Michael addition process. This method provides a facile strategy to access a range of structurally diverse 3,3′-disubstituted oxindoles, which feature an intriguing combination of two privileged motifs including 3-pyrrolyl-substituted-oxindoles and 2,3-dihydrobenzofurans substructures, in excellent results. [ABSTRACT FROM AUTHOR]

An efficient asymmetric [4+2] cycloaddition of 1-((2-aryl)vinyl)naphthalen-2-ols and in situ generated ortho-quinone methides with chiral phosphoric acid as the catalyst was developed. This reaction enables the highly enantioselective synthesis of chiral polysubstituted chromanes bearing multiple contiguous stereogenic centers in excellent yields and stereoselectivities (up to 99% yield, >95 : 5 dr and >99% ee). [ABSTRACT FROM AUTHOR]

Double-platelet, single-platelet and spherical ZnO microcrystals were fabricated via a facile and controllable hydrothermal method. The morphology of the ZnO microcrystals and the exposure ratio of the (001) crystal surface were regulated by adjusting the pH of the solution. The ZnO microcrystals were modified with Pd nanoparticle loading by simple calcining, and the interaction of Pd nanoparticles (NPs) on the ZnO crystal surface increased its oxygen vacancy content. A micro-amount (0.05 wt%) of Pd NP-doped ZnO double-platelets (D-ZnO-0.05) enhanced the gas sensing of the sensor to 3.5 times that of pure double-platelet ZnO. The gas sensing results indicate that D-ZnO-0.05 exhibits a high response (71.2 for NO2 with 25 ppm), fast response/recovery (25 s/21 s), and superior long-term stability (remained at around 95.5% after 35 days). The enhancement in the gas sensing could be attributed to the catalysis of Pd NPs and the increase in the number of oxygen vacancies as a result of Pd loading. The band structure of D-ZnO-0.05 could be effectively tuned by introducing Pd nanoparticles, as shown in density functional theory (DFT) calculations. The Pd dopant and oxygen vacancies reduce the band gap of the ZnO(001) crystal materials, resulting in excellent sensor performance. It is believed that the D-ZnO-0.05 microcrystals could provide inspiration for crystal growth studies and high NO2 gas sensing. [ABSTRACT FROM AUTHOR]

An efficient organocatalytic cyclization strategy was developed to synthesize pharmacologically interesting bicyclic imidazoline derivatives. Morita–Baylis–Hillman carbonates were applied as C3 electrophiles to react with N,C-dinucleophiles for the first time, yielding the desired products in good to excellent yields with outstanding diastereoselectivities. The optically pure bicyclic imidazolines were expeditiously prepared by utilizing the readily available chiral ketene aminals as building blocks. The products were found to inhibit MDM2–p53 binding and cell proliferation. The most potent compound 5c induced the accumulation of MDM2, p53 and p21 proteins in HCT116 cells and blocked interaction between MDM2 and p53. [ABSTRACT FROM AUTHOR]

A highly enantioselective aza-Friedel–Crafts reaction of structurally new ketimines with indoles and pyrrole is developed by using a chiral phosphoric acid as the catalyst. This protocol enables the first enantioselective synthesis of isoquinoline-1,3(2H,4H)-dione derivatives in good to excellent yields (up to 99% yield) and excellent enantioselectivities (up to ＞99% ee). [ABSTRACT FROM AUTHOR]

A highly efficient cyclopropanation of diazo compounds and electron-deficient alkenes under metal- and catalyst-free conditions was developed. The use of water as the sole solvent dramatically increased the efficiency of the reaction. This on-water synthesis approach featured numerous advantages, including high yield, broad substrate scope and environmentally friendly conditions. Moreover, a simple substrate-engineering strategy was used in the reaction system to realise the unprecedented diastereodivergent synthesis of functionalised cyclopropane derivatives with remarkable stereoselectivities. [ABSTRACT FROM AUTHOR]

Crosslinker-free electrochemically-derived graphene oxide membranes are found to be extraordinarily stable in aqueous solutions and exhibit superior ionic sieving performance because of their unique chemical structure. [ABSTRACT FROM AUTHOR]

We report a novel Pd(0) loaded metal–organic framework (MOF) catalyst, namely Pd@Zn2(azoBDC)2(dabco). The efficient catalytic activity and good recyclability of the heterogeneous catalyst carrier are demonstrated through the probe reduction reaction of 4-nitrophenol (NP) to 4-aminophenol (AP) by sodium borohydride (NaBH4). [ABSTRACT FROM AUTHOR]

We here provide the first report on the construction of nanoparticles formulating highly potent cytotoxic therapeutics using albumin. Maytansinoid DM1 can be efficiently integrated into albumin nanoparticles, resulting in remarkable alleviation of in vivo drug toxicity and expanding the repertoire of albumin technology available for cancer therapy. [ABSTRACT FROM AUTHOR]

A novel water-soluble mitochondria-targeted ratiometric fluorescent probe (Cl-2) is presented. Cl-2 can respond selectively to SO2 derivatives within 1 min. Notably, Cl-2 can be used to monitor successfully the concentration change of endogenously generated SO2 derivatives in living cells. [ABSTRACT FROM AUTHOR]

Actuators can directly convert various types of energy into mechanical motions. In this work, we constructed a novel air working ionic actuator by sandwiching sulfuric acid–poly(vinyl alcohol) (H2SO4–PVA) gel electrolyte between two pieces of reduced graphene oxide/polyaniline (r-GO/PANI) nanocomposite film based electrode, in which the PANI nanoparticles were uniformly decorated onto the r-GO sheet surfaces through an in situ polymerization method. A combination of the supramechanical properties, electrical conductivity, large surface area of the individual graphene sheets and excellent electrochemical properties of the PANI component results in the composite electrode having good mechanical properties and a high electrochemical capacitance. Later tests indicated that the actuator could be stimulated under a low driving voltage (≤0.5 V) without trade-off actuator strokes, and showed excellent long-term actuation durability. Under a 0.5 V operating voltage, the actuation strain of the r-GO/PANI actuator could reach 0.327%, corresponding to a 30 MPa generated stress. We attribute the excellent actuation performance to the synergistic effect of the r-GO sheets and the PANI component. [ABSTRACT FROM AUTHOR]

A novel metal-free hydrogen evolution reaction catalyst made of poly(3,4-dinitrothiophene)/SWCNT was developed. This catalyst presents a good hydrogen evolution reaction activity with a lower overpotential than metallic catalysts. Its performance was optimized to an overpotential of ca. 0.040 V and a hydrogen generation rate of 44.2 μmol h -- 1 cm -- 2. [ABSTRACT FROM AUTHOR]

A convenient hydrothermal method has been developed for the controllable synthesis of various nanostructures of manganese oxides and their derivatives through modified redox reactions between Mn2+and the combinative oxidizer of KBrO3/KX (X = Cl, Br, I). The morphologies and oxidation states of the products could be modulated simply by changing the anions in KX to regulate the oxidizability of the combinative oxidizer. With KBrO3/KBr as the oxidizer, potassium manganese oxide (KMO) nanowires are obtained owing to the appropriate oxidizability of the oxidizer as well as the assistance of ion-intercalated effect. The KMO nanowires exhibit the electrochemical capacitance of about 134.2 F g−1at the scan rate of 10 mV s−1and superior cycling stability as revealed by cyclic voltammetry and charge/discharge measurements, implying their potential application in supercapacitors for electrical storage. [ABSTRACT FROM AUTHOR]

The feasibility of employing azulene-like molecules as a new type of high performance substitution-free molecular rectifier has been explored using NEGF-DFT calculation. The electronic transport behaviors of metal-molecule-metal junctions consisting of various azulene-like dithiol molecules are investigated, which reveals that the azulene-like molecules exhibit high conductance and bias-dependent rectification effects. Among all the substitution-free azulene-like structures, cyclohepta[b]cyclopenta[g]naphthalene exhibits the highest rectification ratio, revealing that the all fused aromatic ring structure and an appropriate separation between the pentagon and heptagon rings are essential for achieving both high conductance and high rectification ratio. The rectification ratio can be increased by substituting the pentagon ring with electron-withdrawing group and/or the heptagon ring with electron donating groups. Further increase of the rectification ratio may also be obtained by lithium adsorption on the pentagon ring. This work reveals that azulene-like molecules may be used as a new class of highly conductive unimolecular rectifiers. [ABSTRACT FROM AUTHOR]

The Pd(0)-mediated umpolung reaction of an alkyne to achieve trans -difunctionalization is a potential synthetic methodology, but its insightful activation mechanism of Pd(0)-alkyne interaction has yet to be established. Here, a Pd(0)-π-Lewis base activation mode is proposed and investigated by combining theoretical and experimental studies. In this activation mode, the Pd(0) coordinates to the alkyne group and enhances its nucleophilicity through π-back-donation, facilitating the nucleophilic attack on the aldehyde to generate a trans -Pd(ii)-vinyl complex. Ligand-effect studies reveal that the more electron-donating one would accelerate the reaction, and the cyclization of the challenging flexible C- or O-tethered substrates has been realized. The origin of regioselectivities is also explicated by the newly proposed metal π-Lewis base activation mode., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

The alkyne group can undergo facile transformations under palladium catalysis, such as hydropalladation, Wacker reaction, etc. Here we demonstrate that a chiral Pd 0 complex can chemoselectively dihapto-coordinate to the alkyne moiety of 2-indolyl propiolates, and raise the Highest Occupied Molecular Orbital (HOMO)-energy ofthe deactivated heteroarenes via π-Lewis base catalysis. As a result, asymmetric C3-selective Friedel-Crafts addition to activated alkenes occurs, finally affording [3 + 2] or [3 + 4] annulation products with high enantioselectivity and exclusive E -selectivity. Moreover, this π-Lewis base vinylogous HOMO-activation strategy can be extended to remote Friedel-Crafts reaction of diverse five-membered heteroarenes tethered to a 2-enone or 2-acrylate motif with imines or 1-azadienes, and excellent enantiocontrol is generally achieved for the multifunctional adducts, which can be effectively converted to diverse frameworks with higher molecular complexity. In addition, NMR and density functional theory calculation studies are conducted to elucidate the catalytic mechanism., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Metal oxide sensors face the challenge of high response and fast recovery at low operating temperatures for the detection of toxic and flammable hydrogen sulfide (H 2 S) gases. Herein, novel In-doped ZnO with a sunflower-like structure and tunable surface properties was rationally synthesized. The substitutional In atom in the ZnO crystal can dramatically enhance the concentration of oxygen vacancies (O v ), the In-ZnO sites are responsible for fast recovery, and the formation of sub-stable sulfide intermediates gives rise to the high response towards H 2 S. As a result, the response of the optimized 4In-ZnO sensor is 3538.36 to 50 ppm H 2 S at a low operating temperature of 110 °C, which is 106 times higher than that of pristine ZnO. Moreover, the response time and recovery time to 50 ppm H 2 S are 100 s and 27 s, respectively, with high selectivity and stability. First-principles calculations revealed that 4In-ZnO with rich O v exhibited higher adsorption energy for the H 2 S molecule than pristine ZnO, resulting in effortless H 2 S detection. Our work lays the foundation for the rational design of highly sensitive gas sensors through precise doping of atoms in oxygen-rich vacancies in semiconductor materials.

Restacking of 2D nanomaterials is often deemed to be detrimental to their applications. In contrast to this common notion, here we demonstrate that tightly packed stacked MoS2 exhibits a higher electrocatalytic activity for hydrogen evolution than the more loosely stacked ones.

Many highly active electrocatalysts for the reduction of N2 to NH3 (NRR) have been synthesized but suffer from poor selectivity. One crucial reason is that the adsorption of hydrogen often dominates at the active centers at applied voltage, which leads to the competitive hydrogen evolution reaction. This work used density functional theory (DFT) calculations to develop a class of stable polyoxometalate-based electrocatalysts including phosphomolybdic-, phosphotungstic-, silicotungstic-, and silicomolybdic-acid supported Ru single atoms to efficiently catalyze the NRR process with an overpotential lower than 0.25 V. More importantly, phosphomolybdic- and phosphotungstic acid-supported Ru electrocatalysts can achieve high selectivity at applied voltage. This work offers useful insights into designing high-performance polyoxometalate-based electrocatalysts for the NRR.

Double-platelet, single-platelet and spherical ZnO microcrystals were fabricated via a facile and controllable hydrothermal method. The morphology of the ZnO microcrystals and the exposure ratio of the (001) crystal surface were regulated by adjusting the pH of the solution. The ZnO microcrystals were modified with Pd nanoparticle loading by simple calcining, and the interaction of Pd nanoparticles (NPs) on the ZnO crystal surface increased its oxygen vacancy content. A micro-amount (0.05 wt%) of Pd NP-doped ZnO double-platelets (D-ZnO-0.05) enhanced the gas sensing of the sensor to 3.5 times that of pure double-platelet ZnO. The gas sensing results indicate that D-ZnO-0.05 exhibits a high response (71.2 for NO2 with 25 ppm), fast response/recovery (25 s/21 s), and superior long-term stability (remained at around 95.5% after 35 days). The enhancement in the gas sensing could be attributed to the catalysis of Pd NPs and the increase in the number of oxygen vacancies as a result of Pd loading. The band structure of D-ZnO-0.05 could be effectively tuned by introducing Pd nanoparticles, as shown in density functional theory (DFT) calculations. The Pd dopant and oxygen vacancies reduce the band gap of the ZnO(001) crystal materials, resulting in excellent sensor performance. It is believed that the D-ZnO-0.05 microcrystals could provide inspiration for crystal growth studies and high NO2 gas sensing.

A novel water-soluble mitochondria-targeted ratiometric fluorescent probe (Cl-2) is presented. Cl-2 can respond selectively to SO2 derivatives within 1 min. Notably, Cl-2 can be used to monitor successfully the concentration change of endogenously generated SO2 derivatives in living cells.

A fundamental understanding of the properties of various metal/graphene nanostructures is of great importance for realising their potential applications in electronics and spintronics. The electronic and magnetic properties of three metal/graphene adducts (metal = Li, Co or Fe) are investigated using first-principles calculation. It is predicated that the metal/graphene adducts have strong affinity to aromatic molecule 1,2-dichlorobenzene (DCB), and the resultant DCB-metal/graphene sandwich structures are much more stable than the simple DCB/graphene adduct. Importantly, it is found that the adsorption of DCB slightly enhances the magnetic moment of the Co/graphene, but turns the Fe/graphene from magnetic to nonmagnetic. A detailed theoretical explanation of the different magnetic properties of the DCB/Co/graphene and DCB/Fe/graphene is achieved based on their different d-band splitting upon DCB adsorption. In addition, the transport property study indicates that the Fe/graphene is a better sensing material for DCB than the pristine graphene.