Metal–organic frameworks (MOFs) have been extensively used for single‐site catalysis and light harvesting, but their application in multicomponent photocatalysis is unexplored. We report here the ...successful incorporation of an IrIII photoredox catalyst and a NiII cross‐coupling catalyst into a stable Zr12 MOF, Zr12‐Ir‐Ni, to efficiently catalyze C−S bond formation between various aryl iodides and thiols. The proximity of the IrIII and NiII catalytic components to each other (ca. 0.6 nm) in Zr12‐Ir‐Ni greatly facilitates electron and thiol radical transfers from Ir to Ni centers to reach a turnover number of 38 500, an order of magnitude higher than that of its homogeneous counterpart. This work highlights the opportunity in merging photoredox and organometallic catalysts in MOFs to effect challenging organic transformations.
Business merger: The incorporation of both an IrIII photoredox catalyst and a NiII cross‐coupling catalyst into a stable Zr12 metal–organic framework (MOF) affords a solid dual photocatalyst for C−S coupling between aryl iodides and thiols. By facilitating electron and thiophenol radical transfers from Ir to Ni centers, the MOF photocatalyst exhibits an order of magnitude higher catalytic activity than its homogeneous counterpart.
Abstract
Porous organic polymers (POPs) have emerged as a novel class of porous materials that are synthesized by the polymerization of various organic monomers with different geometries and ...topologies. The molecular tunability of organic building blocks allows the incorporation of functional units for photocatalytic organic transformations. Here, we report the synthesis of two POP‐based photocatalysts via homopolymerization of vinyl‐functionalized diaryl dihydrophenazine (DADHP) monomer (
POP1
) and copolymerization of vinyl‐functionalized DADHP and 2,2′‐bipyridine monomers (
POP2
). The fluorescence lifetimes of DADHP units in the POPs significantly increased, resulting in enhanced photocatalytic performances over homogeneous controls.
POP1
is highly effective in catalysing visible‐light‐driven C−N bond forming cross‐coupling reactions. Upon coordination with Ni
2+
ions,
POP2‐Ni
shows strong synergy between photocatalytic and Ni catalytic cycles due to the confinement effect within the POP framework, leading to high efficiency in energy, electron, and organic radical transfer.
POP2‐Ni
displays excellent activity in catalysing C−P bond forming reactions between diarylphosphine oxides and aryl iodides. They increased the photocatalytic activities by more than 30‐fold in C−N and C−P cross‐coupling reactions. These POP catalysts were readily recovered via centrifugal separation and reused in six catalytic cycles without loss of activities. Thus, photosensitizer‐based POPs provide a promising platform for heterogeneous photocatalytic organic transformations.
More and more tourists are sharing their travel feelings and posting their real experiences on the Internet, generating tourism big data. Online travel reviews can fully reflect tourists' emotions, ...and mining and analyzing them can provide insight into the value of them. In order to analyze the potential value of online travel reviews by using big data technology and machine learning technology, this paper proposes an improved support vector machine (SVM) algorithm based on travel consumer sentiment analysis and builds an Hadoop Distributed File System (HDFS) system based on Map-Reduce model. Firstly, Internet travel reviews are pre-processed for sentiment analysis of the review text. Secondly, an improved SVM algorithm is proposed based on the main features of linear classification and kernel functions, so as to improve the accuracy of sentiment word classification. Then, HDFS data nodes are deployed on the basis of Hadoop platform with the actual tourism application context. And based on the Map-Reduce programming model, the map function and reduce function are designed and implemented, which greatly improves the possibility of parallel processing and reduces the time consumption at the same time. Finally, an improved SVM algorithm is implemented under the built Hadoop platform. The test results show that online travel reviews can be an important data source for travel big data recommendation, and the proposed method can quickly and accurately achieve travel sentiment classification.
The magnetic properties of many magnetic materials can be controlled by external stimuli. The principal focus here is on the thermal, photochemical, electrochemical, and chemical control of phase ...transitions that involve changes in magnetization. The molecular compounds described herein range from metal complexes, through pure organic compounds to composite materials. Most of the Review is devoted to the properties of valence‐tautomeric compounds, molecular magnets, and spin‐crossover complexes, which could find future application in memory devices or optical switches.
Under control: The behavior of certain magnetic materials can be controlled by external stimuli such as temperature, light, and pressure. Typical examples of such switchable materials are valence‐tautomeric compounds, molecular photomagnets, and spin‐crossover complexes, which could find application in memory devices or optical switches.
The jet breaks in the afterglow light curves of short gamma-ray bursts (SGRBs), rarely detected so far, are crucial for estimating the half-opening angles of the ejecta (θj) and hence the neutron ...star merger rate. In this work, we report the detection of jet decline behaviors in GRB 150424A and GRB 160821B, and find θj ∼ 0.1 rad. Together with five events reported before 2015 and three others "identified" recently (GRB 050709, GRB 060614, and GRB 140903A), we have a sample consisting of nine SGRBs and one long-short GRB with reasonably estimated θj. In particular, three Swift bursts in the sample have redshifts z ≤ 0.2, with which we estimate the local neutron star merger rate density to be or if the narrowly beamed GRB 061201 is excluded. Inspired by the typical θj ∼ 0.1 rad found currently, we further investigate whether the off-beam GRBs (in the uniform jet model) or the off-axis events (in the structured jet model) can significantly enhance the GRB/GW association. For the former, the enhancement is at most moderate, while for the latter the enhancement can be much greater and a high GRB/GW association probability of ∼10% is possible. We also show that the data of GRB 160821B may contain a macronova/kilonova emission component with a temperature of ∼3100 K at ∼3.6 days after the burst and more data are needed to ultimately clarify.
Very recently the NICER collaboration published the first-ever accurate measurement of mass and radius together for PSR J0030+0451, a nearby isolated quickly rotating neutron star (NS). In this work ...we set the joint constraints on the equation of state (EoS) and some bulk properties of NSs with the data of PSR J0030+0451, GW170817, and some nuclear experiments. The piecewise polytropic expansion method and the spectral decomposition method have been adopted to parameterize the EoS. The resulting constraints are consistent with each other. Assuming the maximal gravitational mass of nonrotating NS MTOV lies between 2.04M and 2.4M , with the piecewise method the pressure at twice nuclear saturation density is measured to be at the 90% level. For an NS with canonical mass of 1.4M , we have the moment of inertia , tidal deformability , radius , and binding energy at the 90% level, which are improved in comparison to the constraints with the sole data of GW170817. These conclusions are drawn for the mass/radius measurements of PSR J0030+0451 by Riley et al. For the measurements of Miller et al., the results are rather similar.
Recent interest has surged in using heterogeneous carriers to boost synergistic photocatalysis for organic transformations. Heterogeneous catalysts not only facilitate synergistic enhancement of ...distinct catalytic centers compared to their homogeneous counterparts, but also allow for the easy recovery and reuse of catalysts. This mini‐review summarizes recent advancements in developing heterogeneous carriers, including metal–organic frameworks, covalent–organic frameworks, porous organic polymers, and others, for synergistic catalytic reactions. The advantages of porous materials in heterogeneous catalysis originate from their ability to provide a high surface area, facilitate enhanced mass transport, offer a tunable chemical structure, ensure the stability of active species, and enable easy recovery and reuse of catalysts. Both photosensitizers and catalysts can be intricately incorporated into suitable porous carriers to create heterogeneous dual photocatalysts for organic transformations. Notably, experimental evidence from reported cases has shown that the catalytic efficacy of heterogeneous catalysts often surpasses that of their homogeneous analogues. This enhanced performance is attributed to the proximity and confinement effects provided by the porous nature of the carriers. It is expected that porous carriers will provide a versatile platform for integrating diverse catalysts, thus exhibiting superior performance across a range of organic transformations and appealing prospect for industrial applications.
Porous materials including metal–organic frameworks (MOFs), covalent–organic frameworks (COFs), and porous organic polymers (POPs) have recently been established as an ideal platform to enhance synergistic photocatalysis for organic transformations. Benefitting from the designability of these molecular materials, both photosensitizers and catalysts can be intricately incorporated into the porous carriers, leading to greatly enhanced performance over their homogeneous counterparts.
Abstract
We perform a hierarchical Bayesian inference to investigate the population properties of the coalescing compact binaries involving at least one neutron star (NS). With the current ...gravitational-wave (GW) observation data, we can rule out none of the double Gaussian, single Gaussian, and uniform NS mass distribution models, though a specific double Gaussian model inferred from the Galactic NSs is found to be slightly more preferred. The mass distribution of black holes (BHs) in the neutron star–black hole (NSBH) population is found to be similar to that in the Galactic X-ray binaries. Additionally, the ratio of the merger rate densities between NSBHs and BNSs is estimated to be ∼3:7. The spin properties of the binaries, though constrained relatively poorly, play a nontrivial role in reconstructing the mass distribution of NSs and BHs. We find that a perfectly aligned spin distribution can be ruled out, while a purely isotropic distribution of spin orientation is still allowed. To evaluate the feasibility of reliably determining the population properties of NSs in the coalescing compact binaries with upcoming GW observations, we perform simulations with a mock population. We find that with 100 detections (including BNSs and NSBHs) the mass distribution of NSs can be well determined, and the fraction of BNSs can also be accurately estimated.
Preparation of reliable, stable, and highly responsive gas-sensing devices for the detection of acetone has been considered to be a key issue for the development of accurate disease diagnosis systems ...via exhaled breath. In this paper, novel CeO2 nanodot-decorated WO3 nanowires are successfully synthesized through a sequential hydrothermal and thermolysis process. Such CeO2 nanodot-decorated WO3 nanowires exhibited a remarkable enhancement in acetone-sensing performance based on a miniaturized micro-electromechanical system device, which affords high response (S = 1.30–500 ppb, 1.62–2.5 ppm), low detection limit (500 ppb), and superior selectivity toward acetone. The improved performance of the acetone sensor is likely to be originated from the fast carrier transportation of WO3 nanowires, the formation of WO3–CeO2 heterojunctions, and the existence of large amounts of oxygen vacancies in CeO2. The improved reaction thermodynamics and sensing mechanisms have also been revealed by the specific band alignment and X-ray photoelectron spectroscopy analysis.
We report the design of two new metal–organic frameworks (MOFs), Ru-TBP and Ru-TBP-Zn, based on Ru2 secondary building units (SBUs) and porphyrin-derived tetracarboxylate ligands. The proximity of ...Ru2 SBUs to porphyrin ligands (∼1.1 nm) facilitates multielectron transfer from excited porphyrins to Ru2 SBUs to enable efficient visible-light-driven hydrogen evolution reaction (HER) in neutral water. Photophysical and electrochemical studies revealed oxidative quenching of excited porphyrin by Ru2 SBUs as the initial step of the HER process and the energetics of key intermediates in the catalytic cycle. Our work provides a new strategy to building multifunctional MOFs with synergistic ligands and SBUs for efficient photocatalysis.
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