Lewis Acid Transition-Metal-Catalyzed Hydrogen Activation: Structures,Mechanisms, and Reactivities

As a new type of bifunctional catalyst, the Lewis acid transition-metal (LA-TM) catalysts have been widely applied for hydrogen activation. This study presents a mechanistic framework to understand the LA-TM-catalyzed H₂ activation through DFT studies. The mer(trans)-homolytic cleavage, the fac(cis)-homolytic cleavage, the synergetic heterolytic cleavage, and the dissociative heterolytic cleavage should be taken as general mechanisms for the field of LA-TM catalysis. Four typical LA-TM catalysts, the Z-type κ⁴-L₃B-Rh complex tri(azaindolyl)borane-Rh, the X-type κ³-L₂B-Co complex bis-phosphino-boryl (PBP)-Co, the η²-BC-type κ³-L₂B-Pd complex diphosphine-borane (DPB)-Pd, and the Z-type κ²-LB-Pt complex (boryl)iminomethane (BIM)-Pt are selected as representative models to systematically illustrate their mechanistic features and explore the influencing factors on mechanistic variations. Our results indicate that the tri(azaindolyl)borane-Rh catalyst favors the synergetic heterolytic mechanism; the PBP-Co catalyst prefers the mer(trans)-homolytic mechanism; the DPB-Pd catalyst operates through the fac(cis)-homolytic mechanism, whereas the BIM-Pt catalyst tends to undergo the dissociative heterolytic mechanism. The mechanistic variations are determined by the coordination geometry, the LA-TM bonding nature, the electronic structure of the TM center, and the flexibility or steric effect of the LA ligands. The presented mechanistic framework should provide helpful guidelines for LA-TM catalyst design and reaction developments.     

[2]Pseudorotaxane-Based Supramolecular Optical Indicator for the Visual Detection of Cellular Cyanide Excretion

Cyanide is extremely hazardous to living organisms and the environment. Owing to its wide range of applications and high toxicity, the development of functional materials for cyanide detection and sensing is highly desirable. Host–guest complexation between bis(p-phenylene)-34-crown-10 H and N-methylacridinium salt G remarkably decreases the detection limit for cyanide anions compared with that of the guest itself. The [2]pseudorotaxane selectively recognizes the cyanide anion with high optical sensitivity as a result of the nucleophilic addition of the cyanide anion at the 9-position of G . The host–guest complexation is further incorporated into supramolecular materials for the visual detection of cyanide anions, especially the detection of cellular cyanide excretion with a detection limit of 0.6 μm . This supramolecular method provides an extremely distinct strategy for the visual detection of cyanide anions.     

A Renal‐Clearable Duplex Optical Reporter for Real‐Time Imaging of Contrast‐Induced Acute Kidney Injury

Despite its high morbidity and mortality, contrast‐induced acute kidney injury (CIAKI) remains a diagnostic dilemma because it relies on in vitro detection of insensitive late‐stage blood and urinary biomarkers. We report the synthesis of an activatable duplex reporter (ADR) for real‐time in vivo imaging of CIAKI. ADR is equipped with chemiluminescence and near‐infrared fluorescence (NIRF) signaling channels that can be activated by oxidative stress (superoxide anion, O₂^.?) and lysosomal damage (N‐acetyl‐β‐d ‐glucosaminidase, NAG), respectively. By virtue of its high renal clearance efficiency (80 % injected doses after 24 h injection), ADR detects sequential upregulation of O₂^.? and NAG in the kidneys of living mice prior to a significant decrease in glomerular filtration rate (GFR) and tissue damage in the course of CIAKI. ADR outperforms the typical clinical assays and detects CIAKI at least 8 h (NIRF) and up to 16 h (chemiluminescence) earlier.     

Solvent Effect on the Photocatalytic Activity of g-C3N4/BiOBr and its Effect on Degradation of Acetochlor

Russian Journal of Physical Chemistry A - g-C3N4/BiOBr composites were obtained via solvothermal method. XRD, SEM, FTIR, UV–Vis DRS, BET, and BJH methods were used to characterize the...     

Integrating photocatalytic reduction of CO_2 with selective oxidation of tetrahydroisoquinoline over InP–In_2O_3 Z-scheme p-n junction

The development of a facile strategy to construct stable hierarchal porous heterogeneous photocatalysts remains a great challenge for efficient CO_2 reduction. Additionally, hole-trapping sacrificial agents(e.g., triethanolamine, triethylamine, and methanol) are mostly necessary, which produce useless chemicals, and thus cause costs/environmental concerns. Therefore,utilizing oxidation ability of holes to develop an alternative photooxidation reaction to produce value-added chemicals, especially coupled with CO_2 photoreduction, is highly desirable. Here, an in situ partial phosphating method of In_2O_3 is reported for synthesizing In P–In_2O_3 p-n junction. A highly selective photooxidation of tetrahydroisoquinoline(THIQ) into value-added dihydroisoquinoline(DHIQ) is to replace the hole driven oxidation of typical sacrificial agents. Meanwhile, the photoelectrons of In P–In_2O_3 p-n junction can induce the efficient photoreduction of CO_2 to CO with high selectivity and stability. The evolution rates of DHIQ and CO are 2 and 3.8 times higher than those of the corresponding In_2O_3 n-type precursor, respectively. In situ irradiated X-ray photoelectron spectroscopy and electron spin resonance are utilized to confirm that the direct Z-scheme mechanism of In P–In_2O_3 p-n junction accelerate the efficient separation of photocarriers.     

First-Principles Investigation of β-FeOOH for Hydrogen Evolution: Identifying Reactive Sites and Boosting Surface Reactions

Akaganeite (β-FeOOH) is a widely investigated candidate for photo(electro)catalysis, such as water splitting. Nevertheless, insights into understanding the surface reaction between water and β-FeOOH, in particular, the hydrogen evolution reaction (HER), are still insufficient. Herein, a set of first-principles calculations on pristine β-FeOOH and halogen-substituted β-FeOOH are applied to evaluate the HER performance through the computational hydrogen electrode model. The results show that the HER on β-FeOOH tends to occur at Fe sites on the (010) surface, and palladium and nickel are found to serve as excellent co-catalysts to boost the HER process, due to the remarkably reduced free energy change of hydrogen adsorption upon loading on the surface of β-FeOOH, demonstrating great potential for efficient water splitting.     

Effects of imperfect experimental conditions on stress waves in SHPB experiments

Experimental and numerical simulations were undertaken to estimate the effects of imperfect conditions on stress waves in split Hopkinson pressure bar(SHPB)experiments. The photonic Doppler velocimetry(PDV) measurement results show that the rise and fall times of an incident wave increases with an increasing inclination angle;also, the fluctuations of the incident wave disappear gradually with the increase of inclination angle. The following characteristics for various defects in the SHPB were obtained by numerical simulation:(1) the influence of a curved bar was negligible;(2) misalignment modestly affects the fluctuation characteristics, and bending waves were generated at this condition;(3) inclination and indentation of the impact endsurface had a great impact on the incident waves, and both of them increase the rise time of the incident wave by increasing the degree of defects. In view of the results, misalignment,inclination, and indentation in SHPB experiments should be minimized.