Unpaired 3d Electrons on Atomically Dispersed Cobalt Centres in Coordination Polymers Regulate both Oxygen Reduction Reaction (ORR) Activity and Selectivity for Use in Zinc–Air Batteries

Reversible oxygen conversion is important for various green energy technologies. Herein we synthesize a series of bimetallic coordination polymers by varying the Ni/Co ratio and using HITP (HITP=2,3,6,7,10,11‐hexaiminotriphenylene) as the ligand, to interrogate the role of metal centres in modulating the activity of the oxygen reduction reaction (ORR). Co₃HITP₂ and Ni₃HITP₂ are compared. Unpaired 3d electrons in Co₃HITP₂ result in less coplanarity but more radical character. Thus, despite of a reduced crystallinity and conductivity, the best ORR activity, comparable to 20 % Pt/C, is obtained for Co₃HITP₂, showing the 3d orbital configuration of the metal centre promotes ORR. Experimental and DFT studies show a transition of ORR pathway from four‐electron for Co₃HITP₂ to two‐electron for Ni₃HITP₂. Rechargeable zinc–air batteries using Co₃HITP₂ as the air cathode catalyst demonstrate excellent energy efficiency and stability.     

Bridging Small Molecules to Conjugated Polymers: Efficient Thermally Activated Delayed Fluorescence with a Methyl‐Substituted Phenylene Linker

Based on a “TADF + Linker” strategy (TADF=thermally activated delayed fluorescence), demonstrated here is the successful construction of conjugated polymers that allow highly efficient delayed fluorescence. Small molecular TADF blocks are linked together using a methyl‐substituted phenylene linker to form polymers. With the growing number of methyl groups on the phenylene, the energy level of the local excited triplet state (³LE_b) from the delocalized polymer backbone gradually increases, and finally surpasses the charge‐transfer triplet state (³CT). As a result, the diminished delayed fluorescence can be recovered for the tetramethyl phenylene containing polymer, revealing a record‐high external quantum efficiency (EQE) of 23.5 % (68.8 cd A^?1, 60.0 lm W^?1) and Commission Internationale de l′Eclairage (CIE) coordinates of (0.25, 0.52). Combined with an orange‐red TADF emitter, a bright white electroluminescence is also obtained with a peak EQE of 20.9 % (61.1 cd A^?1, 56.4 lm W^?1) and CIE coordinates of (0.36, 0.51).     

Responsive Exosome Nano‐bioconjugates for Synergistic Cancer Therapy

Exosomes hold great potential in therapeutic development. However, native exosomes usually induce insufficient effects in vivo and simply act as drug delivery vehicles. Herein, we synthesize responsive exosome nano‐bioconjugates for cancer therapy. Azide‐modified exosomes derived from M1 macrophages are conjugated with dibenzocyclooctyne‐modified antibodies of CD47 and SIRPα (aCD47 and aSIRPα) through pH‐sensitive linkers. After systemic administration, the nano‐bioconjugates can actively target tumors through the specific recognition between aCD47 and CD47 on the tumor cell surface. In the acidic tumor microenvironment, the benzoic‐imine bonds of the nano‐bioconjugates are cleaved to release aSIRPα and aCD47 that can, respectively, block SIRPα on macrophages and CD47, leading to abolished “don't eat me” signaling and improved phagocytosis of macrophages. Meanwhile, the native M1 exosomes effectively reprogram the macrophages from pro‐tumoral M2 to anti‐tumoral M1.     

Unraveling the Impact of Gold(I)–Thiolate Motifs on the Aggregation‐Induced Emission of Gold Nanoclusters

Aggregation‐induced emission (AIE) provides an efficient strategy to synthesize highly luminescent metal nanoclusters (NCs), however, rational control of emission energy and intensity of metal NCs is still challenging. This communication reveals the impact of surface Au^I‐thiolate motifs on the AIE properties of Au NCs, by employing a series of water‐soluble glutathione (GSH)‐coordinated Au complexes and NCs as a model ([Au₁₀SR₁₀], [Au₁₅SR₁₃], [Au₁₈SR₁₄], and [Au₂₅SR₁₈]^?, SR=thiolate ligand). Spectroscopic investigations show that the emission wavelength of Au NCs is adjustable from visible to the near‐infrared II (NIR‐II) region by controlling the length of the Au^I‐SR motifs on the NC surface. Decreasing the length of Au^I‐SR motifs also changes the origin of cluster luminescence from AIE‐type phosphorescence to Au⁰‐core‐dictated fluorescence. This effect becomes more prominent when the degree of aggregation of Au NCs increases in solution.     

Sulfonium‐Based Homolytic Substitution Observed for the Radical SAM Enzyme HemN

Sulfur‐based homolytic substitution (S_H reaction) plays an important role in synthetic chemistry, yet whether such a reaction could occur on the positively charged sulfonium compounds remains unknown. In the study of the anaerobic coproporphyrinogen III oxidase HemN, a radical S‐adenosyl‐l ‐methionine (SAM) enzyme involved in heme biosynthesis, we observed the production of di‐(5′‐deoxyadenosyl)methylsulfonium, which supports a deoxyadenosyl (dAdo) radical‐mediated S_H reaction on the sulfonium center of SAM. The sulfonium‐based S_H reactions were then investigated in detail by density functional theory calculations and model reactions, which showed that this type of reactions is thermodynamically favorable and kinetically competent. These findings represent the first report of sulfonium‐based S_H reactions, which could be useful in synthetic chemistry. Our study also demonstrates the remarkable catalytic promiscuity of the radical SAM superfamily enzymes.     

π‐Interactions between Cyclic Carbocations and Aromatics Cause Zeolite Deactivation in Methanol‐to‐Hydrocarbon Conversion

The understanding of catalyst deactivation represents one of the major challenges for the methanol‐to‐hydrocarbon (MTH) reaction over acidic zeolites. Here we report the critical role of intermolecular π‐interactions in catalyst deactivation in the MTH reaction on zeolites H‐SSZ‐13 and H‐ZSM‐5. π‐interaction‐induced spatial proximities between cyclopentenyl cations and aromatics in the confined channels and/or cages of zeolites are revealed by two‐dimensional solid‐state NMR spectroscopy. The formation of naphtalene as a precursor to coke species is favored due to the reaction of aromatics with the nearby cyclopentenyl cations and correlates with both acid density and zeolite topology.     

Influence of the molding angle on tensile properties of FDM parts with orthogonal layering

Fused deposition molding (FDM) is one of the most widely used three‐dimensional (3D) printing technologies. This paper explores the influence of the forming angle on the tensile properties of FDM specimens. Orthogonal layering details were studied through experiments, theory, and finite element simulations. The stiffness and strength of the specimens were analyzed using the classical laminated plate theory and the Tsai–Wu failure criterion. The experimental process was simulated using finite element simulations. Results show that it is feasible to predict the stiffness and strength of FDM specimens using classical laminated plate theory and the Tsai–Wu failure criterion. A molding angle of 45° leads to specimens with maximized tensile properties. Numerical simulations show that changing the molding angle changes the internal stress and deformation fields inside samples, leading to FDM samples with different mechanical properties due to the orthogonal layers at different molding angles.     

Flame retardancy and smoke suppression of silicone foams with microcapsulated aluminum hypophosphite and zinc borate

The flame‐retardant microcapsules were successfully fabricated with an aluminum hypophosphite (AHP) core. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) were used to verify that AHP was encapsulated in the microcapsules, and thermogravimetry analysis showed that microencapsulated AHP (MAHP) possessed higher thermal stability than that of AHP. Then, a flame‐retardant and smoke suppression system for silicone foams (SiFs) was obtained through a synergistic effect of MAHP and zinc borate (2ZnO·3B₂O₃·3.5H₂O). The mechanical properties, flame retardance, and smoke suppression of SiFs with MAHP and zinc borate were tested using the tensile test, limiting oxygen index (LOI) test, UL‐94 test, and cone calorimeter test. The mechanical properties indicated that the tensile strength and elongation at break of SiFs could evidently improve with the incorporation of MAHP. Compared with pure SiF, SiF8 with 4.5‐wt% MAHP and 1.5‐wt% zinc borate could achieve an LOI value of 30.7 vol% and an UL‐94 V‐0 rating, the time to ignition amplified almost six times, the peak heat release rate and total heat release were 51.10% and 46.00% less than that of pure SiF, respectively, the fire performance index increased nearly 13 times, and the fire growth index value was only 13.18% of pure SiF. Moreover, the partial substitution of zinc borate imparted a substantial improvement in both flame retardancy and smoke suppression. Especially, the peak smoke production rate and total smoke production of SiF8 were merely 38.46% and 38.84% of pure SiF.     

Analysis of thermodynamic characteristics of imidazolium-based ionic liquid on coal

To investigate the effects of ionic liquids (ILs) on the oxidative combustion characteristics of coal, the oxidation characteristics of ILs on coal, such as characteristic temperature, thermal mass loss rate, and oxidation kinetics characteristic parameters, were determined. The results the [BMIm][I]-treated coal samples increased cracking temperature (T₁), maximum oxidization mass gain (T₂), ignition temperature (T₃), burnout temperature (T₄), minimum thermal rate (T_a), maximum thermal energy (T_b), and maximum thermal rate (T_c) by 33.2, 29.3, 20.7, 42.8, 11.4, 23.0, and 27.9 °C, respectively. The increase mass ratio of coal samples treated with ILs increased and decreased at the water evaporation and thermal decomposition stages, respectively. The apparent activation energy (E_a) of coal samples treated with ILs increased, and the mechanism function also changed accordingly. These showed that the ILs improved the thermal stability of the coal samples in the stages of absorbing oxygen and increased mass, and the loss of combustion. The ILs caused damage to the molecular structure of the coal and ultimately effected changes in the combustion performance. In addition, the [BMIm][BF₄] hardly weakens the inhibitory effectiveness of the coal sample over time; coal spontaneous combustion could be effectively inhibited.

     

Preparation of Antioxidant Protein Hydrolysates from Pleurotus geesteranus and Their Protective Effects on H2O2 Oxidative Damaged PC12 Cells

Pleurotus geesteranus is a promising source of bioactive compounds. However, knowledge of the antioxidant behaviors of P. geesteranus protein hydrolysates (PGPHs) is limited. In this study, PGPHs were prepared with papain, alcalase, flavourzyme, pepsin, and pancreatin, respectively. The antioxidant properties and cytoprotective effects against oxidative stress of PGPHs were investigated using different chemical assays and H₂O₂ damaged PC12 cells, respectively. The results showed that PGPHs exhibited superior antioxidant activity. Especially, hydrolysate generated by alcalase displayed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (91.62%), 2,2-azino-bis (3-ethylbenzothia zoline-6-sulfonic acid) (ABTS) radical scavenging activity (90.53%), ferric reducing antioxidant power, and metal ion-chelating activity (82.16%). Analysis of amino acid composition revealed that this hydrolysate was rich in hydrophobic, negatively charged, and aromatic amino acids, contributing to its superior antioxidant properties. Additionally, alcalase hydrolysate showed cytoprotective effects on H₂O₂-induced oxidative stress in PC12 cells via diminishing intracellular reactive oxygen species (ROS) accumulation by stimulating antioxidant enzyme activities. Taken together, alcalase hydrolysate of P. geesteranus protein can be used as beneficial ingredients with antioxidant properties and protective effects against ROS-mediated oxidative stress.