Unveiling the role of proton concentration in dinuclear metal complexes for boosting photocatalytic CO2 reduction.

The reaction kinetics of photocatalytic CO2 reduction is highly dependent on the transfer rate of electrons and protons to the CO2 molecules adsorbed on catalytic centers. Studies on uncovering the proton effect in catalysts on photocatalytic activity of CO2 reduction are significant but rarely reported. In this paper, we, from the molecular level, revealed that the photocatalytic activity of CO2 reduction is closely related to the proton availability in catalysts. Specifically, four dinuclear Co(II) complexes based on Robson-type ligands with different number of carboxylic groups (-nCOOH; n = 0, 2, 4, 6) were designed and synthesized. All these complexes show photocatalytic activity for CO2 reduction to CO in a water-containing system upon visible-light illumination. Interestingly, the CO yields increase positively with the increase of the carboxylic-group number in dinuclear Co(II) complexes. The one containing -6COOH shows the best photocatalytic activity for CO2 reduction to CO, with the TON value reaching as high as 10,294. The value is 1.8, 3.4, and 7.8 times higher than those containing -4COOH, -2COOH, and -0COOH, respectively. The high TON value also makes the dinuclear Co(II) complex with -6COOH outstanding among reported homogeneous molecular catalysts for photocatalytic CO2 reduction. Control experiments and density functional theory calculation indicated that more carboxylic groups in the catalyst endow the catalyst with more proton relays, thus accelerating the proton transfer and boosting the photocatalytic CO2 reduction. This study, at a molecular level, elucidates that more carboxylic groups in catalysts are beneficial for boosting the reaction kinetics of photocatalytic CO2 reduction.

Dual electronic effects achieving a high-performance Ni(II) pincer catalyst for CO2 photoreduction in a noble-metal-free system.

A carbazolide-bis(NHC) NiII catalyst (1; NHC, N-heterocyclic carbene) for selective CO2 photoreduction was designed herein by a one-stone-two-birds strategy. The extended π-conjugation and the strong σ/π electron-donation characteristics (two birds) of the carbazolide fragment (one stone) lead to significantly enhanced activity for photoreduction of CO2 to CO. The turnover number (TON) and turnover frequency (TOF) of 1 were ninefold and eightfold higher than those of the reported pyridinol-bis(NHC) NiII complex at the same catalyst concentration using an identical Ir photosensitizer, respectively, with a selectivity of ∼100%. More importantly, an organic dye was applied to displace the Ir photosensitizer to develop a noble-metal-free photocatalytic system, which maintained excellent performance and obtained an outstanding quantum yield of 11.2%. Detailed investigations combining experimental and computational studies revealed the catalytic mechanism, which highlights the potential of the one-stone-two-birds effect.

Ordered heterogeneity of molecular photosensitizer toward enhanced photocatalysis.

SignificanceThe photosensitizer is one of the important components in the photocatalytic system. Molecular photosensitizers have well-defined structures, which is beneficial in revealing the catalysis mechanism and helpful for further structural design and performance optimization. However, separation and recycling of the molecular photosensitizers is a great problem. Loading them into/on two/three-dimensional supports through covalent bonds, electrostatic interactions, and supramolecular interactions is a method that enhances their separation and recycling capability. Nonetheless, the structures of the resulting composites are unclear. Thus, the development of highly crystalline heterogeneity methods for molecular photosensitizers, albeit greatly challenging, is meaningful and desirable in photocatalysis, through which heterogeneous photosensitizers with well-defined structures, definite catalysis mechanisms, and good catalytic performance would be expected.

A2 reactive astrocyte-derived exosomes alleviate cerebral ischemia-reperfusion injury by delivering miR-628.

Ischemia and hypoxia activate astrocytes into reactive types A1 and A2, which play roles in damage and protection, respectively. However, the function and mechanism of A1 and A2 astrocyte exosomes are unknown. After astrocyte exosomes were injected into the lateral ventricle, infarct volume, damage to the blood-brain barrier (BBB), apoptosis and the expression of microglia-related proteins were measured. The dual luciferase reporter assay was used to detect the target genes of miR-628, and overexpressing A2-Exos overexpressed and knocked down miR-628 were constructed. qRT-PCR, western blotting and immunofluorescence staining were subsequently performed. A2-Exos obviously reduced the infarct volume, damage to the BBB and apoptosis and promoted M2 microglial polarization. RT-PCR showed that miR-628 was highly expressed in A2-Exos. Dual luciferase reporter assays revealed that NLRP3, S1PR3 and IRF5 are target genes of miR-628. After miR-628 was overexpressed or knocked down, the protective effects of A2-Exos increased or decreased, respectively. A2-Exos reduced pyroptosis and BBB damage and promoted M2 microglial polarization through the inhibition of NLRP3, S1PR3 and IRF5 via the delivery of miR-628. This study explored the mechanism of action of A2-Exos and provided new therapeutic targets and concepts for treating cerebral ischemia.

Controllable Silver Release for Efficient Treatment of Drug-Resistant Bacterial-Infected Wounds.

The use of traditional Ag-based antibacterial agents is usually accompanied by uncontrollable silver release, which makes it difficult to find a balance between antibacterial performance and biosafety. Herein, we prepared a core-shell system of ZIF-8-derived amorphous carbon-coated Ag nanoparticles (Ag@C) as an ideal research model to reveal the synergistic effect and structure-activity relationship of the structural transformation of carbon shell and Ag core on the regulation of silver release behavior. It is found that Ag@C prepared at 600 °C (AC6) exhibits the best ion release kinetics due to the combination of relatively simple shell structure and lower crystallinity of the Ag core, thereby exerting stronger antibacterial properties (>99.999 %) at trace doses (20 µg mL-1) compared with most other Ag-based materials. Meanwhile, the carbon shell prevents the metal Ag from being directly exposed to the organism and thus endows AC6 with excellent biocompatibility. In animal experiments, AC6 can effectively promote wound healing by inactivating drug-resistant bacteria while regulating the expression of TNF-α and CD31. This work provides theoretical support for the scientific design and clinical application of controllable ion-releasing antibacterial agents.

Electronic Modulation in Homonuclear Dual-Atomic Catalysts for Enhanced CO2 Electroreduction.

Homonuclear dual-atomic catalysts showcase unique electronic modulation due to their dual metal centres, providing new direction in development of efficient catalysts for CO2 electroreduction. This article highlights a few cutting-edge homonuclear dual-atomic catalysts, focusing on their inherent advantages in efficient and selective CO2 electroreduction, to spotlight the potential application of dual-atomic catalysts in CO2 electroreduction.

Covalent Bonding of Salen Metal Complexes with Pyrene Chromophores to Porous Polymers for Photocatalytic Hydrogen Evolution.

The development of low-cost and efficient photocatalysts to achieve water splitting to hydrogen (H2) is highly desirable but remains challenging. Herein, we design and synthesize two porous polymers (Co-Salen-P and Fe-Salen-P) by covalent bonding of salen metal complexes and pyrene chromophores for photocatalytic H2 evolution. The catalytic results demonstrate that the two polymers exhibit excellent catalytic performance for H2 generation in the absence of additional noble-metal photosensitizers and cocatalysts. Particularly, the H2 generation rate of Co-Salen-P reaches as high as 542.5 µmol g-1 h-1, which is not only 6 times higher than that of Fe-Salen-P but also higher than a large amount of reported Pt-assisted photocatalytic systems. Systematic studies show that Co-Salen-P displays faster charge separation and transfer efficiencies, thereby accounting for the significantly improved photocatalytic activity. This study provides a facile and efficient way to fabricate high-performance photocatalysts for H2 production.

Discovery of cinnamamide/ester triazole hybrids as potential treatment for Alzheimer's disease.

Developing multitargeted ligands as promising therapeutics for Alzheimer's disease (AD) has been considered important. Herein, a novel class of cinnamamide/ester-triazole hybrids with multifaceted effects on AD was developed based on the multitarget-directed ligands strategy. Thirty-seven cinnamamide/ester-triazole hybrids were synthesized, with most exhibiting significant inhibitory activity against Aß-induced toxicity at a single concentration in vitro. The most optimal hybrid compound 4j inhibited copper-induced Aß toxicity in AD cells. its action was superior to that of donepezil and memantine. It also moderately inhibited intracellular AChE activity and presented favorable bioavailability and blood-brain barrier penetration with low toxicity in vivo. Of note, it ameliorated cognitive impairment, neuronal degeneration, and Aß deposition in Aß1-42-injured mice. Mechanistically, the compound regulated APP processing by promoting the ADAM10-associated nonamyloidogenic signaling and inhibiting the BACE1-mediated amyloidogenic pathway. Moreover, it suppressed intracellular AChE activity and tau phosphorylation. Therefore, compound 4j may be a promising multitargeted active molecule against AD.

Dinuclear metal synergistic catalysis for energy conversion.

Catalysts featuring dinuclear metal sites are regarded as superior systems compared with their counterparts with mononuclear metal sites. The dinuclear metal sites in catalysts with appropriate spatial separations and geometric configurations can confer the dinuclear metal synergistic catalysis (DMSC) effect, and thus boost the catalytic performance, in particular for reactions involving multiple reactants, intermediates and products. In this review, we summarize the related reports on the design and synthesis of both homogeneous and heterogeneous dinuclear metal catalysts, and their applications in energy conversion reactions, including photo-/electro-catalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO2 reduction reaction (CO2RR), and N2 reduction reaction (N2RR). Particularly, we focus on the analysis of the relationship between the catalyst structure and catalytic performances, where the design principles are presented. Finally, we discuss the challenges in the design and preparation of dinuclear metal catalysts with the DMSC effect and present a perspective on the future development of dinuclear metal catalysts in energy conversion. This review aims to comprehensively summarize the up-to-date research progress on the synthesis and energy-related application of dinuclear metal catalysts and provide guidance for designing energy-conversion catalysts with superior performances.

Boosting CO2 Photoreduction to Formate or CO with High Selectivity over a Covalent Organic Framework Covalently Anchored on Graphene Oxide.

Covalent organic frameworks (COFs) have been widely studied in photocatalytic CO2 reduction reaction (CO2 RR). However, pristine COFs usually exhibit low catalytic efficiency owing to the fast recombination of photogenerated electrons and holes. In this study, we fabricated a stable COF-based composite (GO-COF-366-Co) by covalently anchoring COF-366-Co on the surface of graphene oxide (GO) for the photocatalytic CO2 reduction. Interestingly, in absolute acetonitrile (CH3 CN), GO-COF-366-Co shows a high selectivity of 94.4 % for the photoreduction of CO2 to formate, with a formate yield of 15.8 mmol/g, which is approximately four times higher than that using the pristine COF-366-Co. By contrast, in CH3 CN/H2 O (v : v=4 : 1), the main product for the photocatalytic CO2 reduction over GO-COF-366-Co is CO (96.1 %), with a CO yield as high as 52.2 mmol/g, which is also approximately four times higher than that using the pristine COF-366-Co. Photoelectrochemical experiments demonstrate the covalent bonding of COF-366-Co and GO to form the GO-COF-366-Co composite facilitates charge separation and transfer significantly, thereby accounting for the enhanced catalytic activity. In addition, theoretical calculations and in situ Fourier transform infrared spectroscopy reveal H2 O can stabilize the *COOH intermediate to further form a *CO intermediate via O-H(aq)⋅⋅⋅O(*COOH) hydrogen bonding, thus explaining the regulated photocatalytic performance.

A Planar-Structured Dinuclear Cobalt(II) Complex with Indirect Synergy for Photocatalytic CO2-to-CO Conversion.

Dinuclear metal synergistic catalysis (DMSC) has been proved an effective approach to enhance catalytic efficiency in photocatalytic CO2 reduction reaction, while it remains challenge to design dinuclear metal complexes that can show DMSC effect. The main reason is that the influence of the microenvironment around dinuclear metal centres on catalytic activity has not been well recognized and revealed. Herein, we report a dinuclear cobalt complex featuring a planar structure, which displays outstanding catalytic efficiency for photochemical CO2-to-CO conversion. The turnover number (TON) and turnover frequency (TOF) values reach as high as 14457 and 0.40 s-1 respectively, 8.6 times higher than those of the corresponding mononuclear cobalt complex. Control experiments and theoretical calculations revealed that the enhanced catalytic efficiency of the dinuclear cobalt complex is due to the indirect DMSC effect between two CoII ions, energetically feasible one step two-electron transfer process by Co2 I,I intermediate to afford Co2 II,II(CO2 2-) intermediate and fast mass transfer closely related with the planar structure.

Modulating the Microenvironments of Robust Metal Hydrogen-Bonded Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution.

Hydrogen-bonded organic frameworks (HOFs) are outstanding candidates for photocatalytic hydrogen evolution. However, most of reported HOFs suffer from poor stability and photocatalytic activity in the absence of Pt cocatalyst. Herein, a series of metal HOFs (Co2-HOF-X, X=COOMe, Br, tBu and OMe) have been rationally constructed based on dinuclear cobalt complexes, which exhibit exceptional stability in the presence of strong acid (12 M HCl) and strong base (5 M NaOH) for at least 10 days. More impressively, by varying the -X groups of the dinuclear cobalt complexes, the microenvironment of Co2-HOF-X can be modulated, giving rise to obviously different photocatalytic H2 production rates, following the -X group sequence of -COOMe>-Br>-tBu>-OMe. The optimized Co2-HOF-COOMe shows H2 generation rate up to 12.8 mmol g-1 h-1 in the absence of any additional noble-metal photosensitizers and cocatalysts, which is superior to most reported Pt-assisted photocatalytic systems. Experiments and theoretical calculations reveal that the -X groups grafted on Co2-HOF-X possess different electron-withdrawing ability, thus regulating the electronic structures of Co catalytic centres and proton activation barrier for H2 production, and leading to the distinctly different photocatalytic activity.

Water-Etched Approach to Hierarchically Porous Metal-Organic Frameworks with High Stability.

The development of hierarchically porous metal-organic frameworks (MOFs) with high stability is desirable to expand their applications but remains challenging. Herein, an anionic sodalite-type microporous MOF (Yb-TTCA; TTCA3- = triphenylene-2,6,10-tricarboxylate) was synthesized, which shows outstanding catalytic activities for the cycloaddition of CO2 into cyclic carbonates. Moreover, the microporous Yb-TTCA can be transformed into a hierarchical micro- and mesoporous Yb-TTCA by water treatment with the mesopore sizes of 2 to 12 nm. The hierarchically porous Yb-TTCA (HP-Yb-TTCA) not only exhibits a high thermal stability up to 500 °C but also shows a high chemical stability in aqueous solutions with pH values ranging from 2 to 12. In addition, the HP-Yb-TTCA displays enhanced performance for the removal of organic dyes in comparison with microporous Yb-TTCA. This work provides a facile way to construct hierarchically porous MOF materials.

Bone marrow mesenchymal stem cell-derived exosomal miR-193b-5p reduces pyroptosis after ischemic stroke by targeting AIM2.

BACKGROUND: Ischemic stroke represents a major factor causing global morbidity and death. Bone marrow mesenchymal stem cell (BMSC)-derived exosomes (Exos) have important effects on treating ischemic stroke. Here, we investigated the therapeutic mechanism by which BMSC-derived exosomal miR-193b-5p affects ischemic stroke. METHODS: luciferase assay was performed to evaluate the regulatory relationship of miR-193b-5p with absent in melanoma 2 (AIM2). Additionally, an oxygen-glucose deprivation/reperfusion (OGD/R) model was constructed for the in vitro assay, while a middle cerebral artery occlusion (MCAO) model was developed for the in vivo assay. After exosome therapy, lactate dehydrogenase and MTT assays were conducted to detect cytotoxicity and cell viability, while PCR, ELISA, western blotting assay, and immunofluorescence staining were performed to detect changes in the levels of pyroptosis-related molecules. TTC staining and TUNEL assays were performed to assess cerebral ischemia/reperfusion (I/R) injury. RESULTS: In the luciferase assay, miR-193b-5p showed direct binding to the 3'-untranslated region of AIM2. In both in vivo and in vitro assays, the injected exosomes could access the sites of ischemic injury and could be internalized. In the in vitro assay, compared to normal BMSC-Exos, miR-193b-5p-overexpressing BMSC-Exos showed greater effects on increasing cell viability and attenuating cytotoxicity; AIM2, GSDMD-N, and cleaved caspase-1 levels; and IL-1ß/IL-18 generation. In the in vivo assay, compared to normal BMSC-Exos, miR-193b-5p-overexpressing BMSC-Exos showed greater effects on decreasing the levels of these pyroptosis-related molecules and infarct volume. CONCLUSION: BMSC-Exos attenuate the cerebral I/R injury in vivo and in vitro by inhibiting AIM2 pathway-mediated pyroptosis through miR-193b-5p delivery.

An Analysis of Respiratory Muscle Paralysis of Adult Patients in Guillain-Barré Syndrome: A Retrospective Analysis.

Respiratory muscle paralysis is known as a very common complication of Guillain-Barré syndrome (GBS). However, most research has focused on its later stages rather than its earlier stages, including the prognosis of patients with this condition, or factors that act as early predictors of risk. Therefore, our study aimed to identify early predictors of respiratory muscle paralysis in patients with GBS and determine the short-term prognosis of such patients. We recruited 455 GBS patients (age ≥ 18) who had been hospitalized in the First Affiliated Hospital of Harbin Medical University between 2016 and 2021, retrospectively. We recorded clinical and laboratory data and used linear and logistic regression analysis to investigate the relationship between early clinical, examination results, and subsequent respiratory muscle paralysis. Among the 455 patients, 129 were assigned to a respiratory muscle paralysis group and 326 were assigned to a non-respiratory muscle paralysis group. Compared with the non-affected group, the time from onset to admission was shorter (p = 0.0003), and the Medical Research Council (MRC) score at admission and discharge was smaller in the affected group (p < 0.0001). Compared with the non-affected group, the affected group had higher Hughes and Erasmus GBS Respiratory Insufficiency Score (EGRIS) scores at admission and longer hospital stays (p < 0.0001). Patients in the affected group were more likely to have bulbar palsy and lung infections (p < 0.0001). To conclude, bulbar palsy, a higher EGRIS score and Hughes score at admission, a lower MRC score, and a shorter time between onset and admission, are all predictive risk factors for respiratory muscle paralysis in patients with GBS. An increase in any of these factors increases the risk of muscle paralysis. Patients with respiratory muscle paralysis have a poorer short-term prognosis than those without respiratory muscle paralysis. Therefore, we should attempt to identify patients with one or more of these characteristics in the early stages of admission, provide ventilation management, and administer IMV treatment if necessary.

Photosystem II Inspired NiFe-Based Electrocatalysts for Efficient Water Oxidation via Second Coordination Sphere Effect.

The mismatched fast-electron-slow-proton process in the electrocatalytic oxygen evolution reaction (OER) severely restricts the catalytic efficiency. To overcome these issues, accelerating the proton transfer and elucidating the kinetic mechanism are highly sought after. Herein, inspired by photosystem II, we develop a family of OER electrocatalysts with FeO6 /NiO6 units and carboxylate anions (TA2- ) in the first and second coordination sphere, respectively. Benefiting from the synergistic effect of the metal units and TA2- , the optimized catalyst delivers superior activity with a low overpotential of 270 mV at 200 mA cm-2 and excellent cycling stability over 300 h. A proton-transfer-promotion mechanism is proposed by in situ Raman, catalytic tests, and theoretical calculations. The TA2- (proton acceptor) can mediate proton transfer pathways by preferentially accepting protons, which optimizes the O-H adsorption/activation process and reduces the kinetic barrier for O-O bond formation.

Building 2D/2D CdS/MOLs Heterojunctions for Efficient Photocatalytic Hydrogen Evolution.

2D lamellar materials can offer high surface area and abundant reactive sites, thus showing an appealing prospect in photocatalytic hydrogen evolution. However, it is still difficult to build cost-efficient photocatalytic hydrogen evolution systems based on 2D materials. Herein, an in situ growth method is employed to build 2D/2D heterojunctions, with which 2D Ni-based metal-organic layers (Ni-MOLs) are closely grown on 2D porous CdS (P-CdS) nanosheets, affording traditional P-CdS/Ni-MOL heterojunction materials. Impressively, the optimized P-CdS/Ni-MOL catalyst exhibits superior photocatalytic hydrogen evolution performance, with an H2 yield of 29.81 mmol g-1 h-1 . This value is 7 and 2981 times higher than that of P-CdS and Ni-MOLs, respectively, and comparable to those of reported state of the art catalysts. Photocatalytic mechanism studies reveal that the enhanced photocatalytic performance can be attributed to the 2D/2D intimate interface between P-CdS and Ni-MOLs, which facilitates the fast charge carriers' separation and transfer. This work provides a strategy to develop 2D MOL-based photocatalysts for sustainable energy conversion.

Modulating the Electronic Structures of Dual-Atom Catalysts via Coordination Environment Engineering for Boosting CO2 Electroreduction.

Dual-atom catalysts (DACs) have emerged as efficient electrocatalysts for CO2 reduction owing to the synergistic effect between the binary metal sites. However, rationally modulating the electronic structure of DACs to optimize the catalytic performance remains a great challenge. Herein, we report the electronic structure modulation of three Ni2 DACs (namely, Ni2 -N7 , Ni2 -N5 C2 and Ni2 -N3 C4 ) by the regulation of the coordination environments around the dual-atom Ni2 centres. As a result, Ni2 -N3 C4 exhibits significantly improved electrocatalytic activity for CO2 reduction, not only better than the corresponding single-atom Ni catalyst (Ni-N2 C2 ), but also higher than Ni2 -N7 and Ni2 -N5 C2 DACs. Density functional theory (DFT) calculations revealed that the high electrocatalytic activity of Ni2 -N3 C4 for CO2 reduction could be attributed to the electronic structure modulation to the Ni centre and the resulted proper binding energies to COOH* and CO* intermediates.

Recent advances of the function of sphingosine 1-phosphate (S1P) receptor S1P3.

Known as a variety of sphingolipid metabolites capable of performing various biological activities, sphingosine 1-phosphate (S1P) is commonly found in platelets, red blood cells, neutrophils, lymph fluid, and blood, as well as other cells and body fluids. S1P comprises five receptors, namely, S1P1-S1P5, with the distribution of S1P receptors exhibiting tissue selectivity to some degree. S1P1, S1P2, and S1P3 are extensively expressed in a wide variety of different tissues. The expression of S1P4 is restricted to lymphoid and hematopoietic tissues, while S1P5 is primarily expressed in the nervous system. S1P3 plays an essential role in the pathophysiological processes related to inflammation, cell proliferation, cell migration, tumor invasion and metastasis, ischemia-reperfusion, tissue fibrosis, and vascular tone. In this paper, the relevant mechanism in the role of S1P3 is summarized.

Incorporation of Chromophores into Metal-Organic Frameworks for Boosting CO2 Conversion.

The exploitation of highly stable and active catalysts for the conversion of CO2 into valuable fuels is desirable but is a great challenge. Herein, we report that the incorporation of chromophores into metal-organic frameworks (MOFs) could afford robust catalysts for efficient CO2 conversion. Specifically, a porous Nd(III) MOF (Nd-TTCA; TTCA3- = triphenylene-2,6,10-tricarboxylate) was constructed by incorporating one-dimensional Nd(CO2)n chains and TTCA3- ligands, which exhibits a very high stability, retaining its framework not only in the air at 300 °C for 2 h but also in boiling aqueous solutions at pH 1-12 for 7 days. More importantly, Nd-TTCA has achieved a 5-fold improvement in photocatalytic activity for reducing CO2 to HCOOH and a 10-fold improvement in catalytic activity for the cycloaddition of CO2 into cyclic carbonate in comparison to those of H3TTCA itself. This work gives a new strategy to design efficient artificial crystalline catalysts for CO2 conversion.