Search

Supramolecular systems consisting of covalent organic frameworks (COFs) and Ni complex are designed for robust photocatalytic reduction of CO2. Multiple heteroatom‐hydrogen bonding between the COF and Ni complex is identified to play a decisive role in the photoexcited electron transfer across the liquid‐solid interface. The diminution of steric groups on COF or metal complex can optimize catalytic performance, which is more attributable to the enhanced hydrogen‐bond interaction rather than their intrinsic activity. The photosystem with relatively strong strength of hydrogen bonds exhibits remarkable photocatalytic CO2‐to‐CO conversion, far superior to photosystems with supported atomic Ni or metal complex alone in the absence of hydrogen‐bond effect. Such heteroatom‐hydrogen bonds bridging electron transport pathway confers supramolecular system with high photocatalytic performance, providing an avenue to rationally design efficient and steadily available photosystems. [ABSTRACT FROM AUTHOR]

Supramolecular systems consisting of covalent organic frameworks (COFs) and Ni complex are designed for robust photocatalytic reduction of CO2. Multiple heteroatom‐hydrogen bonding between the COF and Ni complex is identified to play a decisive role in the photoexcited electron transfer across the liquid‐solid interface. The diminution of steric groups on COF or metal complex can optimize catalytic performance, which is more attributable to the enhanced hydrogen‐bond interaction rather than their intrinsic activity. The photosystem with relatively strong strength of hydrogen bonds exhibits remarkable photocatalytic CO2‐to‐CO conversion, far superior to photosystems with supported atomic Ni or metal complex alone in the absence of hydrogen‐bond effect. Such heteroatom‐hydrogen bonds bridging electron transport pathway confers supramolecular system with high photocatalytic performance, providing an avenue to rationally design efficient and steadily available photosystems. [ABSTRACT FROM AUTHOR]

Abstract: Covalent organic frameworks (COFs) are emerging as a class of photocatalyst for solar energy utilization. The separation of photogenerated excitons in COFs is crucial for their photocatalytic performance. Herein, we report a strategy to tune the electronic structure of COFs by implanting Zn ions within the framework to facilitate the separation and utilization of the photoinduced charges. Zn ions are incorporated within the shell of hollow COF cages (Zn@H‐TpPa) by a sacrificial template method with a formation of hollow cages. The implantation of Zn ions within the framework results in a redistribution of electron density and an increment of the polarity of the COF, as evidenced by experimental and computational analyses, and thus contributes to the separation and transport of charge carries. The Zn@H‐TpPa shows enhanced photocatalytic H2 production efficiency as compared to TpPa. The results demonstrate a new way to optimize the electronic structure of COFs for photocatalysis. [ABSTRACT FROM AUTHOR]

Crystalline covalent organic frameworks (COFs) are porous polymeric semiconductors with network topologies, which are built from the integration of selected organic blocks with covalent bond linkages. They have shown great promise for artificial photosynthesis, owing to broad light harvesting, high crystallinity, and high carrier mobility. This Minireview introduces state‐of‐the‐art COF photocatalysts based on different linkages and discusses the origin of photocatalytic activities for hydrogen evolution. Three typical COF photocatalysts, with linkages including imine (−C=N−), β‐ketoenamine (O=C−C=C−NH−), and vinylene (−C=C−), are discussed with a particular focus on the advancements in synthetic methodologies and structural design, as well as photoelectronic properties that are relevant to photocatalytic performance. The Minireview is expected to elucidate their structure–property relationships and the way to design photoactive COFs with enhanced performances. [ABSTRACT FROM AUTHOR]

Facile fabrication of nanocatalysts consisting of metal nanoparticles (NPs) anchored on a functional support is highly desirable, yet remains challenging. Covalent organic frameworks (COFs) provide an emerging materials platform for structural control and functional design. Here, a facile one‐pot in situ reduction approach is demonstrated for the encapsulation of small Pd NPs into the shell of COF‐derived hollow polyamine spheres (Pd@H‐PPA). In the one‐pot synthetic process, the nucleation and growth of Pd NPs in the cavities of the porous shell take place simultaneously with the reduction of imine linkages to secondary amine groups. Pd@H‐PPA shows a significantly enhanced catalytic activity and recyclability in the tandem dehydrogenation of ammonia borane and selective hydrogenation of nitroarenes through an adsorption–activation–reaction mechanism. The strong interactions of the secondary amine linkage with borane and nitroarene molecules afford a positive synergy to promote the catalytic reaction. Moreover, the hierarchical structure of Pd@H‐PPA allows the accessibility of active Pd NPs to reactants. [ABSTRACT FROM AUTHOR]

Photocatalytic conversion of CO2 into value‐added chemical fuels is a promising approach to address the depletion of fossil energy and environment‐related concerns. Tailor‐making the electronic properties and band structures of photocatalysts is pivotal to improve their efficiency and selectivity in photocatalytic CO2 reduction. Herein, a covalent triazine‐based framework was developed containing electron‐donor triphenylamine and electron‐acceptor triazine components (DA‐CTF). The engineered π‐conjugated electron donor–acceptor dyads in DA‐CTF not only optimized the optical bandgap but also contributed to visible‐light harvesting and migration of photoexcited charge carriers. The activity of photocatalytic CO2 reduction under visible light was significantly improved compared with that of traditional g‐C3N4 and reported covalent triazine‐based frameworks. This study provides molecular‐level insights into the mechanism of photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction into carbonaceous feedstock chemicals is a promising renewable energy technology to convert solar energy and greenhouse gases into chemical fuels. Here, a covalent triazine‐based framework (CTF) is demonstrated as an efficient cocatalyst to reduce CO2 under visible‐light irradiation. The nitrogen‐rich triazine moieties in CTF contribute to CO2 adsorption, while the periodical pore structure of CTF favors the accommodation of CO2 and electron mediator. Immobilization of cobalt species onto CTF promotes the photocatalytic activity with a 44‐fold enhancement over pristine CTF and the optimal CO production rate of the obtained Co/CTFs was up to 50 μmol g−1 h−1. The results of solid‐state UV‐vis diffuse reflectance spectra (UV‐vis DRS), CO2 adsorption and electrochemical impedance spectroscopy (EIS) illustrated that the increased activity was ascribed to the enhanced CO2 capture capacity, improved absorption of visible‐light and facilitated the transfer of charge from CTF to CO2 molecules. The CTF not only serves as a substrate for active Co species, but also bridges the photosensitizer with cobalt catalytic sites for the efficient transfer of photoexcited electrons. This work highlights the capability and ease of fabricating covalent organic framework‐based photocatalytic systems that are potentially useful for energy‐conversion applications. [ABSTRACT FROM AUTHOR]

The protein tyrosine phosphatase PTP1B, which is encoded by PTPN1, is a ubiquitously expressed nonreceptor protein tyrosine phosphatase. PTP1B has long been known to negatively regulate insulin and leptin receptor signalling. Recently, it was reported to be aberrantly expressed in cancer cells and to function as an important oncogene. In this study, we found that PTP1B protein levels are dramatically increased in breast cancer (BC) tissues and that PTP1B promotes the proliferation, and suppresses the apoptosis, of both HER2‐positive and triple‐negative BC cell lines. Bioinformatics analysis identified that the miRNA, miR‐193a‐3p, might potentially target PTP1B. We demonstrate that miR‐193a‐3p regulates PTP1B in BC cells and that it regulates the proliferation and apoptosis of BC cells by targeting PTP1B, both in vitro and in vivo. In conclusion, this study confirms that PTP1B acts as an oncogene in BC and demonstrates that miR‐193a‐3p can serve as a tumour suppressor gene in BC by targeting PTP1B. Dysregulation of miR‐193a‐3p leads to PTP1B overexpression via a post‐transcriptional mechanism in HER2‐positive and triple‐negative breast cancer (BC) cells. The miR‐193a‐3p/PTP1B regulatory axis promotes cell proliferation, suppresses apoptosis and ultimately accelerates BC progression. [ABSTRACT FROM AUTHOR]

The formation mechanism of Mn–Al–O inclusions in Fe–Cr–Mn stainless steel during continuous casting is investigated by industrial trials and thermodynamic calculation. The morphology, composition, and size distribution of inclusions in steel specimens are analyzed by scanning electron microscopy and energy dispersive spectroscopy. The main inclusions change from spherical Ca–Si–O and Ca–Si–Mn–O inclusions during LF refining to Mn–Al–O inclusions in continuous casting slab and hot‐rolled sheet. The size of most Mn–Al–O inclusions containing high MnO content is smaller than 4 µm. The formation of these inclusions is consistent with thermodynamic calculation, which indicates that MnO and Al2O3 inclusions are formed during continuous casting process. The calculation results of MnO and Al2O3 inclusions growth shown that the size of MnO inclusion (4 µm) is much larger than that of Al2O3 inclusion (0.4 µm) at the end of solidification, which also accords with the characteristics of inclusions in continuous casting slab and hot‐rolled sheet. [ABSTRACT FROM AUTHOR]

Abstract: MoS2 quantum dots (QDs)‐modified covalent triazine‐based framework (MoS2/CTF) composites are synthesized through an in situ photodeposition method. MoS2 QDs are well distributed and stabilized on the layers of CTFs by coordination of the frameworks to MoS2. The QDs–sheet interactions between MoS2 and CTFs facilitate interfacial charge transfer and separation. As a consequence, the composites exhibit outstanding photocatalytic activity and stability for hydrogen evolution under visible light irradiation (λ≥420 nm), that exceed those over pristine CTFs and MoS2‐modified g‐C3N4 (MoS2/g‐C3N4) composite, making them promising materials for solar energy conversion. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with hollow structures hold great promise for developing new types of functional materials. Herein, we report a hollow spherical COF with a hierarchical shell, which serves as an effective precursor of B,N-codoped hierarchical hollow carbon spheres. Benefiting from the synergistic effects of hierarchical porosity, high surface area, and B,N-codoping, the as-synthesized carbon spheres show prospective utility as metal-free catalysts in nitroarene reduction. A mechanistic hypothesis is proposed based on theoretical and experimental studies. Boron atoms situated meta to pyridinic N atoms are identified to be the main catalytic active sites. The anti-aromaticity originating from the codoping of B and pyridinic N atoms, not charge distribution and deformation energy, is confirmed to play a pivotal role in the catalytic reaction. [ABSTRACT FROM AUTHOR]

A series of porous imidazolium-based ionic polymers that contain in situ formed Pd nanoparticles (Pd@PIPs) was synthesized by a Suzuki-Miyaura cross-coupling reaction in the presence of SiO2 particles. The hierarchical porosities of Pd@PIPs can be regulated well by adjusting the dosage of SiO2. Pd nanoparticles are formed concomitantly and encapsulated uniformly within the pores of the polymers. The appropriate usage of SiO2 templates results in a clear enhancement of the catalytic activity in the hydrogenation of nitroarenes without the addition of extra Pd species. The excellent catalytic performances are attributed to abundant meso- and macropores that facilitate the mass transfer of substrates during catalytic reactions. [ABSTRACT FROM AUTHOR]

Covalent triazine-based frameworks (CTFs) with a graphene-like layered morphology have been controllably synthesized by the trifluoromethanesulfonic acid-catalyzed nitrile trimerization reactions at room temperature via selecting different monomers. Platinum nanoparticles are well dispersed in CTF-T1, which is ascribed to the synergistic effects of the coordination of triazine moieties and the nanoscale confinement effect of CTFs. CTF-T1 exhibits excellent photocatalytic activity and stability for H2 evolution in the presence of platinum under visible light irradiation ( λ ≥ 420 nm). The activity and stability of CTF-T1 are comparable to those of g-C3N4. Importantly, as a result of the tailorable electronic and spatial structures of CTFs that can be achieved through the judicial selection of monomers, CTFs not only show great potential as organic semiconductor for photocatalysis but also may provide a molecular-level understanding of the inherent heterogeneous photocatalysis. [ABSTRACT FROM AUTHOR]

Two urea-based porous organic frameworks, UOF-1 and UOF-2, were synthesized through a urea-forming condensation of 1,3,5-benzenetriisocyanate with 1,4-diaminobenzene and benzidine, respectively. UOF-1 and UOF-2 possess good hydrophilic properties and high scavenging ability for palladium. Their palladium polymers, PdII/UOF-1 and PdII/UOF-2, exhibit high catalytic activity and selectivity for Suzuki-Miyaura cross-coupling reactions and selective reduction of nitroarenes in water. The catalytic reactions can be efficiently performed at room temperature. Palladium nanoparticles with narrow size distribution were formed after the catalytic reaction and were well dispersed in UOF-1 and UOF-2. XPS analysis confirmed the coordination of the urea oxygen atom with palladium. SEM and TEM images showed that the original network morphology of UOF-1 and UOF-2 was maintained after palladium loading and catalytic reactions. [ABSTRACT FROM AUTHOR]

Three ionic nitrogen-containing chelating ligands ( L1- L3) are synthesized readily through alkylation and quaternization of 2,2′-dipyridylamine. The charge distributions and natural bond orbital analyses of their cations are implemented by using density functional theory calculations. The catalytic performances of their water-soluble palladium complexes are evaluated preliminarily by using the Suzuki-Miyaura cross-coupling reaction, and high catalytic activities of aryl bromides and chlorides are achieved in neat water. The mercury drop test, poison experiments, and TEM analysis are used to demonstrate the formation of palladium nanoparticles (NPs) after the catalytic reaction. The effects of pendant ionic groups in L1- L3 on the catalytic activities and structures of the palladium NPs are disclosed. These NPs are stable in water for several weeks; they are stabilized by synergetic interactions between the chelating coordination of the 2,2′-dipyridylamino group to the surface of the palladium NPs and the electrostatic repulsion of the ionic groups in L1- L3. [ABSTRACT FROM AUTHOR]

The reaction of bis- or tris-chelating nitrogen-containing ligands (L1-L5) with CuI gave rise to five coordination complexes consisting of Cu2I2 dimeric units. L1 in complex 1 adopts a cis conformation and links Cu2I2 into a dinuclear structure. L2 and L3 in complexes 2 and 3 exhibit a trans conformation, and the alternative linkage of L2 or L3 and Cu2I2 results in the formation of a 1D chain. In complex 4, two pyrazolyl-pyridine units of L4 at the same side of the central phenyl ring are connected to Cu2I2 forming a tetranuclear macrocycle, and the third pyrazolyl-pyridine unit at the other side of the central phenyl ring further links the macrocycle into a 1D chain. L5 bridges Cu2I2 in a cis conformation forming a tetranuclear complex, which is very different from 1 owing to the difference of the electronic property between pyrazolyl and triazolyl rings. The coordination nitrogen atoms in two pairs of ortho-positioned nitrogen-containing chelating rings in L1 and L5 are directed toward opposite and the same directions, respectively. Complexes 1- 4 containing pyrazolyl-pyridine units showed luminescence whereas no clear emission was observed in complex 5 containing triazolyl-pyridine units, despite the fact that they were investigated under the same conditions. The application of complexes 1- 5 in the copper(I)-catalyzed Ullmann cross-coupling reaction and azide-alkyne cycloaddition reaction was preliminarily evaluated. [ABSTRACT FROM AUTHOR]

A series of 1,10-phenanthroline derivatives were used as supporting ligands for copper-catalyzed Ullmann reaction in neat water. The catalytic system based on 4,7-dihydroxy-1,10-phenanthroline has demonstrated the promising catalytic performances for aryl bromides. The catalytic system was applicable to a wide scope of substrates, high catalytic activity and selectivity were observed for the reactions of electron-deficient, electron-rich, and heterocyclic aryl bromides with imidazoles containing different steric hindrance. The superior promoting effect of 4,7-dihydroxy-1,10-phenanthroline is attributed to its water solubility under the basic conditions. [ABSTRACT FROM AUTHOR]

A series of click ionic salts 4 a- 4 n was prepared through click reaction of organic azides with alkyne-functionalized imidazolium or 2-methylimidazolium salts, followed by metathesis with lithium bis(trifluoromethanesulfonyl)amide or potassium hexafluorophosphate. All salts were characterized by IR, NMR, TGA, and DSC, and most of them can be classified as ionic liquids. Their steric and electronic properties can be easily tuned and modified through variation of the aromatic or aliphatic substituents at the imidazolium and/or triazolyl rings. The effect of anions and substituents at the two rings on the physicochemical properties was investigated. The charge and orbital distributions based on the optimized structures of cations in the salts were calculated. Reaction of 4 a with PdCl2 produced mononuclear click complex 4 a-Pd, the structure of which was confirmed by single-crystal X-ray diffraction analysis. Suzuki-Miyaura cross-coupling shows good catalytic stability and high recyclability in the presence of PdCl2 in 4 a. TEM and XPS analyses show formation of palladium nanoparticles after the reaction. The palladium NPs in 4 a are immobilized by the synergetic effect of coordination and electrostatic interactions with 1,2,3-triazolyl and imidazolium, respectively. [ABSTRACT FROM AUTHOR]

Frontispiece: A covalent triazine‐based framework (CTF) possessing a graphene‐like layered morphology demonstrates excellent photocatalytic activity and stability in splitting water under visible light irradiation. Due to the tailorable electronic and spatial structures of CTFs, they not only show great potential as organic semiconductors for photocatalysis but also provide a molecular‐level understanding of the inherent heterogeneous photocatalysis. Further details can be found in the article by J. Bi,* W. Fang, L. Li, J. Wang, S. Liang, Y. He, M. Liu, and L. Wu* on page 1799. [ABSTRACT FROM AUTHOR]

Supramolecular systems consisting of covalent organic frameworks (COFs) and Ni complex are designed for robust photocatalytic reduction of CO2. Multiple heteroatom‐hydrogen bonding between the COF and Ni complex is identified to play a decisive role in the photoexcited electron transfer across the liquid‐solid interface. The diminution of steric groups on COF or metal complex can optimize catalytic performance, which is more attributable to the enhanced hydrogen‐bond interaction rather than their intrinsic activity. The photosystem with relatively strong strength of hydrogen bonds exhibits remarkable photocatalytic CO2‐to‐CO conversion, far superior to photosystems with supported atomic Ni or metal complex alone in the absence of hydrogen‐bond effect. Such heteroatom‐hydrogen bonds bridging electron transport pathway confers supramolecular system with high photocatalytic performance, providing an avenue to rationally design efficient and steadily available photosystems. [ABSTRACT FROM AUTHOR]

Supramolecular systems consisting of covalent organic frameworks (COFs) and Ni complex are designed for robust photocatalytic reduction of CO2. Multiple heteroatom‐hydrogen bonding between the COF and Ni complex is identified to play a decisive role in the photoexcited electron transfer across the liquid‐solid interface. The diminution of steric groups on COF or metal complex can optimize catalytic performance, which is more attributable to the enhanced hydrogen‐bond interaction rather than their intrinsic activity. The photosystem with relatively strong strength of hydrogen bonds exhibits remarkable photocatalytic CO2‐to‐CO conversion, far superior to photosystems with supported atomic Ni or metal complex alone in the absence of hydrogen‐bond effect. Such heteroatom‐hydrogen bonds bridging electron transport pathway confers supramolecular system with high photocatalytic performance, providing an avenue to rationally design efficient and steadily available photosystems. [ABSTRACT FROM AUTHOR]

Two urea-based porous organic frameworks are synthesized through an urea-forming condensation of benzenetriisocyanate with 1,4-diaminobenzene and benzidine, respectively. [ABSTRACT FROM AUTHOR]

Health professions preventing and controlling Coronavirus Disease 2019 are prone to skin and mucous membrane injury, which may cause acute and chronic dermatitis, secondary infection and aggravation of underlying skin diseases. This is a consensus of Chinese experts on protective measures and advice on hand-cleaning- and medical-glove-related hand protection, mask- and goggles-related face protection, UV-related protection, eye protection, nasal and oral mucosa protection, outer ear, and hair protection. It is necessary to strictly follow standards of wearing protective equipment and specification of sterilizing and cleaning. Insufficient and excessive protection will have adverse effects on the skin and mucous membrane barrier. At the same time, using moisturizing products is highly recommended to achieve better protection., (© 2020 Wiley Periodicals, Inc.)