Stable Mg Single-Atom Solid Base Catalysts Anchored on Metal-Organic Framework-Derived Nitrogen-Doped Carbon.

Solid base catalysts are widely used in the chemical industry owing to their advantages of environmental friendliness and easy separation. However, their application is limited by basic site aggregation and poor stability. In this study, we report the preparation of magnesium (Mg) single-atom catalysts with high activity and stability by a sublimation-trapping strategy. The Mg net was sublimated as Mg vapor at 620 °C, subsequently transported through argon, and finally trapped on the defects of nitrogen-doped carbon derived from metal-organic framework ZIF-8, producing Mg1/NC. Because of the atomically dispersed Mg sites, the obtained Mg1/NC exhibits high catalytic activity and stability for Knoevenagel condensation of benzaldehyde with malononitrile, which is a typical base-catalyzed reaction. The Mg1/NC catalyst achieves a high efficiency with a turnover frequency of 49.6 h-1, which is much better than that of the traditional counterpart MgO/NC (7.7 h-1). In particular, the activity of Mg1/NC shows no decrease after five catalytic cycles, while that of MgO/NC declines due to the instability of basic sites.

Nanosecond-pulsed plasma protects against bacterial fruit blotch and promotes melon seedling growth.

BACKGROUND: Bacterial fruit blotch (BFB), known as the 'cancer' of cucurbits, is a seed-borne disease of melons caused by Acidovorax citrulli. Traditional chemical treatments for BFB are ineffective and adversely affect the environment. Using dielectric barrier discharge (DBD) nanosecond-pulsed plasma technology, melon seeds were treated to promote germination and growth and to control BFB. RESULTS: Based on the evaluation parameters of seed germination, seedling growth, leaf yellowing and bacterial infection after seed plasma treatments, 9 min at 20 kV was selected as the optimal plasma discharge parameter. In this study, seedling growth was significantly improved after treating melon seeds carrying A. citrulli using this discharge parameter. The number of first true leaves measured on the eighth day was 2.3 times higher and the disease index was reduced by 60.5% compared to the control group. Attenuated total reflectance-Fourier transform infrared measurements show that plasma treatments penetrate the seed coat and denature polysaccharides and proteins in the seed kernel, affecting their growth and sterilization properties. CONCLUSION: Pre-sowing treatment of melon seeds carrying A. citrulli using nanosecond-pulsed plasma technology can effectively control seedling BFB disease and promote melon seedling growth by optimizing DBD parameters. © 2024 Society of Chemical Industry.

Endowing Covalent Organic Frameworks with Photoresponsive Active Sites for Controllable Propylene Adsorption.

Photoresponsive covalent organic frameworks (PCOFs) have emerged as attractive candidates for adsorption, but it is challenging to construct PCOF adsorbents due to structural order loss of covalent organic frameworks (COFs) after introducing photoresponsive motifs and/or tedious steps of postmodification. Here, a facile strategy is developed, by dispersing photoresponsive metal-organic polyhedra (PMOP) into COFs, to endow COFs with photoresponsive adsorption sites. As a proof-of-concept study, a COF with pore size of 4.5 nm and PMOP with suitable molecular size (4.0 and 3.1 nm for trans and cis configuration, respectively) are selected to meet the requirements of proper accommodation space, good guest dispersion, and free isomerization. The structure of COF is well preserved after introducing PMOPs. Interestingly, the obtained photoresponsive host-guest composite (PHGC) adsorbents exhibit photomodulated adsorption capacity on propylene (C3 H6 ) and the change in adsorption capacity can reach up to 43.3% and is stable during multiple cycles. Density functional theory calculations reveal that visible-light irradiation drives the azobenzene motifs in PHGCs to the trans configuration and the adsorption sites are fully open and interact with C3 H6 . UV-light irradiation makes the azobenzene motifs transform to the cis configuration, leading to the shield of the adsorption sites and the consequent release of C3 H6 .

Photo-Induced Construction and Recovery of Cu+ Sites in Metal-Organic Frameworks.

The adjustment of the valence state of metal ions is crucial for various applications because peculiar activity originates from metal ions with specific valence. Cu+ can interact with molecules possessing unsaturated bonds like CO via π-complexation, while Cu2+ doesn't have such ability. Meanwhile, Cu+ sites are easily oxidized to Cu2+ , leading to the loss of activity. Despite great efforts, the development of a facile method to construct and recover Cu+ sites remains a pronounced challenge. Here, for the first time a facile photo-induced strategy is reported to fabricate Cu+ sites in metal-organic frameworks (MOFs) and recover Cu+ after oxidation. The Cu2+ precursor was loaded on NH2 -MIL-125, a typical visible-light responsive Ti-based MOF. Visible light irradiation triggers the formation of Ti3+ from Ti4+ in framework, which reduces the supported Cu2+ in the absence of any additional reducing agent, thus simplifying the process for Cu+ generation significantly. Due to π-complexation interaction, the presence of Cu+ results in remarkably enhanced CO capture capacity (1.16 mmol g-1 ) compared to NH2 -MIL-125 (0.49 mmol g-1 ). More importantly, Cu+ can be recovered conveniently via re-irradiation when it is oxidized to Cu2+ , and the oxidation-recovery process is reversible.

Process-Oriented Smart Adsorbents: Tailoring the Properties Dynamically as Demanded by Adsorption/Desorption.

Adsorptive separation plays a critical role in chemical, food, pharmaceutical, and environmental industries, as well as in many other industrial areas. Adsorbents are most important for adsorptive separation and undergo adsorption and desorption processes to accomplish the specific tasks of separation. In the process of adsorption, adsorbates diffuse into the pore spaces of adsorbents through pore openings, adsorb on active sites via physical or chemical interactions, and subsequently are regenerated by temperature or pressure swings during desorption. In the process of adsorption and desorption, however, the requirements for pore structures and surface properties of adsorbents are different. In general, adsorbents with small pore openings can realize selective adsorption and do not favor desorption; on the other hand, adsorbents with large pore openings are efficient in desorption but at the expense of adsorption selectivity. Remarkably, active sites possessing strong interactions with adsorbates contribute to high selectivity for adsorption, while desorption becomes difficult. The trade-off between adsorption and desorption presents an enormous challenge to develop high-efficiency adsorbents. Restricted by their fixed structures and surface properties, conventional adsorbents are unable to meet the demands of adsorption and desorption processes simultaneously.To confront the obstacles, the development of advanced adsorbents to meet the demand of adsorptive separation are urgent. A key strategy to address such issues lies in dynamically adjusting the pore structures or the surface properties of adsorbents with controllability according to the demands of adsorption/desorption. For instance, pursuant to the requirements of varying pore structures during adsorption/desorption, the pore openings of adsorbents can be customized through dynamic structural change of the decorated stimuli-sensitive motifs by suitable external intervention. In addition, the active sites within the adsorbents can be exposed to enhance the adsorption selectivity or sheltered to accelerate the desorption through stimuli-triggered adsorbent-adsorbate interactions. Hence, we proposed a concept of process-oriented smart adsorbents (POSAs) on the basis of the requirements of the adsorption/desorption processes. The design and development of such POSAs are based on three aspects, namely, pore openings, pore spaces, and adsorption sites of adsorbents.In this Account, we present the progress in the development of POSAs according to the demands of adsorption/desorption processes. A series of POSAs with incorporated stimuli-sensitive motifs were successfully achieved. The versatility of incorporated motifs allows them to tune the pore structures and surface properties of adsorbents dynamically and further to enhance the adsorption and desorption efficiency simultaneously. Based on the concept of POSAs, we hope that this Account could contribute to the development of high-efficiency adsorbents and ultimately promote their applications in practical industrial separation. Moreover, we present an outlook on future trends and challenges on the road toward the development and applications of POSAs.

Photomodulation on Active Sites of Adsorbents: Controllable Adsorption Processes with Improved Efficiency.

Adsorption is a widely applied technique in producing high-purity chemicals with advantages of low energy consumption, high selectivity, and mild operating conditions. However, traditional adsorbents have inflexible properties and suffer from the trade-off between selective adsorption and efficient desorption. Recently, the emerging photoresponsive adsorbents have provided new avenues for adsorption techniques. Active sites of photoresponsive adsorbents can be regulated through steric hindrance or tunable adsorbent-adsorbate interactions. Therefore, variation in adsorptive capacity is able to readily achieve through photomodulation, and the corresponding adsorption/desorption cycles are energy-saving. This concept mainly summarizes recent efforts on the fabrication and application of photoresponsive adsorbents with tunable active sites. Also, the future opportunities and critical challenges of photoregulation on adsorptive sites are presented.

How to handle a delayed or missed dose of edoxaban in patients with non-valvular atrial fibrillation? A model-informed remedial strategy.

AIMS: Edoxaban is a non-vitamin K antagonist oral anticoagulant (NOAC) widely used for the long-term prevention of stroke in patients with non-valvular atrial fibrillation (NVAF). Adherence to NOAC therapy has been unsatisfactory and decreases over time. Remedial strategies are currently used to address the non-adherence events. Current recommendations, however, are generic and not well supported by evidence. The aim of this study was to explore appropriate remedial dosing regimens for non-adherent edoxaban-treated NVAF patients through Monte Carlo simulation. METHODS: Six regimens were compared with the current recommendations of the European Heart Rhythm Association (EHRA) guide based on total deviation time. Both edoxaban plasma concentration and intrinsic Factor Xa activity were considered. Monte Carlo simulations were performed using RxODE based on a published population pharmacokinetic/pharmacodynamic (PK/PD) model. RESULTS: The proposed remedial strategies were different than the EHRA recommendations and were related to the delay time. However, it was found that the missed dose can be administered immediately if the delay time is within 11 h. When the delay is between 12 and 19 h, a half dose followed by a regular dosing schedule is recommended. When the delay time exceeds 19 h, a full dose followed by a half dose is preferred. CONCLUSION: PK/PD modelling and simulation are effective in developing and evaluating the remedial strategies of edoxaban, which can help maximise its therapeutic effect.

Bioactive Dimeric Diterpenoids from Taiwania cryptomerioides (Hayata) and Their Biological Activities.

Taiwania cryptomerioides Hayata is an endangered relict plant belonging to Taxodiaceae, and it is also an endemic plant to China. The decay-resistant of Taiwania timber can provide highly quality wood for building and furniture. Plenty of regenerative of leaves of T. cryptomerioides also has been used as a resource for the discovery of new dimeric diterpenoids. In a search for structurally diverse dimeric diterpenoids and potent bioactive isolates, ten new heterodimeric diterpenoids, taiwaniadducts K-T (1-4, 6, 8-11, and 14), along with five known ones (5, 7, 12, 13, and 15), were isolated from the leaves of T. cryptomerioides. These new compounds were defined by comprehensive spectroscopic analyses, putative biosynthetic pathways, and the values of optical. Biologically, anti-multidrug resistance (MDR) activities of compounds were evaluated. Compounds 4 and 10 exerted a 9.18-fold potentiation effect on bortezmib (BTZ) susceptibility at a tested concentration (20 µM) better than the positive control verapamil. The research of the leaves of T. cryptomerioides not only added the new data to the structural diversity and activities of dimeric diterpenoids but also could provide support for the medical and industrial application of the leaves of this endangered relict plant.

SM22α Deletion Contributes to Neurocognitive Impairment in Mice through Modulating Vascular Smooth Muscle Cell Phenotypes.

Considerable evidence now indicates that cognitive impairment is primarily a vascular disorder. The depletion of smooth muscle 22 alpha (SM22α) contributes to vascular smooth muscle cells (VSMCs) switching from contractile to synthetic and proinflammatory phenotypes in the context of inflammation. However, the role of VSMCs in the pathogenesis of cognitive impairment remains undetermined. Herein, we showed a possible link between VSMC phenotypic switching and neurodegenerative diseases via the integration of multi-omics data. SM22α knockout (Sm22α-/-) mice exhibited obvious cognitive impairment and cerebral pathological changes, which were visibly ameliorated by the administration of AAV-SM22α. Finally, we confirmed that SM22α disruption promotes the expression of SRY-related HMG-box gene 10 (Sox10) in VSMCs, thereby aggravating the systemic vascular inflammatory response and ultimately leading to cognitive impairment in the brain. Therefore, this study supports the idea of VSMCs and SM22α as promising therapeutic targets in cognitive impairment to improve memory and cognitive decline.

[Effects of Rehmanniae Radix and Rehmanniae Radix Praeparata on proteomics and autophagy in mice with type 2 diabetes mellitus induced by high-fat diet coupled with streptozotocin].

To compare the pancreatic proteomics and autophagy between Rehmanniae Radix-and Rehmanniae Radix Praeparata-treated mice with type 2 diabetes mellitus(T2DM). The T2DM mouse model was established by high-fat diet coupled with streptozotocin(STZ, intraperitoneal injection, 100 mg·kg~(-1), once a day for three consecutive days). The mice were then randomly assigned into a control group, low-(5 g·kg~(-1)) and high-dose(15 g·kg~(-1)) Rehmanniae Radix groups, low-(150 mg·kg~(-1)) and high-dose(300 mg·kg~(-1)) catalpol groups, low-(5 g·kg~(-1)) and high-dose(15 g·kg~(-1)) Rehmanniae Radix Praeparata groups, low-(150 mg·kg~(-1)) and high-dose(300 mg·kg~(-1)) 5-hydroxymethyl furfuraldehyde(5-HMF) groups, and a metformin(250 mg·kg~(-1)) group. In addition, a normal group was also set and each group included 8 mice. The pancreas was collected after four weeks of administration and proteomics tools were employed to study the effects of Rehmanniae Radix and Rehmanniae Radix Praeparata on protein expression in the pancreas of T2DM mice. The expression levels of proteins involved in autophagy, inflammation, and oxidative stress response in the pancreatic tissues of T2DM mice were determined by western blotting, immunohistochemical assay, and transmission electron microscopy. The results showed that the differential proteins between the model group and Rehmanniae Radix/Rehmanniae Radix Prae-parata group were enriched in 7 KEGG pathways, such as autophagy-animal, which indicated that the 7 pathways may be associated with T2DM. Compared with the control group, drug administration significantly up-regulated the expression levels of beclin1 and phosphorylated mammalian target of rapamycin(p-mTOR)/mTOR and down-regulated those of the inflammation indicators, Toll-like receptor-4(TLR4) and Nod-like receptor protein 3(NLRP3), in the pancreas of T2DM mice, and Rehmanniae Radix showed better performance. In addition, the expression levels of inducible nitric oxide synthase(iNOS), nuclear factor erythroid 2-related factor 2(Nrf2), and heine oxygenase-1(HO-1) in the pancreas of T2DM mice were down-regulated after drug administration, and Rehmanniae Radix Praeparata demonstrated better performance. The results indicate that both Rehmanniae Radix and Rehmanniae Radix Praeparata can alleviate the inflammatory symptoms, reduce oxidative stress response, and increase the autophagy level in the pancreas of T2DM mice, while they exert the effect on different autophagy pathways.

Transformation of Type III to Type II Porous Liquids by Tuning Surface Rigidity of Rhodium(II)-Based Metal-Organic Polyhedra for CO2 Cycloaddition.

Porous liquids (PLs), a summation of porous hosts and bulky solvents bestowing permanent cavities, are the prominent emerging materials. Despite great efforts, exploration of porous hosts and bulky solvents is still needed to develop new PL systems. Metal-organic polyhedra (MOPs) with discrete molecular architectures can be considered as porous hosts; however, many of them are insoluble entities. Here we report the transformation of type III PL to type II PLs by tuning the surface rigidity of insoluble MOP, Rh24 L24 , in a bulky ionic liquid (IL). Functionalization of N-donor molecules on Rh-Rh axial sites ensue their solubilization in bulky IL which confer type II PLs. Experimental and theoretical studies reveal the bulkiness of IL as per the cage apertures, and the cause of their dissolution as well. The obtained PLs, capturing more CO2 than neat solvent, have depicted higher catalytic activity for CO2 cycloaddition compared to individual MOPs and IL.

Detachable Porous Organic Polymers Responsive to Light and Heat.

Stimuli-responsive porous materials have captured much attention due to the on-demand tunable properties. Most reported stimuli-responsive porous materials are based on molecule isomerism or host-guest interaction, and it is highly desired to develop new types based on different responsive mechanism. Herein, inspired by natural cells which have the ability to fuse and divide induced by external stimulation, we report a new type of stimuli-responsive porous material based on detachment mechanism. A detachable porous organic polymer, namely DT-POP-1, is fabricated from the polymerization of anthracene-containing monomer (AnMon) when irradiated by 365 nm UV light. DT-POP-1 can detach into the monomer AnMon when irradiated with 275 nm UV light or heat. Such polymerization/detachment is reversible. The detachment results in a big difference in porosity and adsorption capacity, making the present detachable porous polymer highly promising in adsorptive separation and drug delivery.

Enhanced CO Adsorption by Modulating the Electron Density Distribution of Graphite-Copper Porphyrin Sorbents with Light.

The photo-responsive adsorption has emerged as a vibrant area, but its current methodology is limited by the well-defined photochromic units and their molecular deformation driven by photo-stimuli. Herein, a methodology of nondeforming photo-responsiveness is successfully exploited. With the exploiting agent of Cu-TCPP framework assembled on the graphite and strongly interacted with it, the sorbent generates two kinds of adsorption sites, over which the electron density distribution of the graphite layer can be modulated at the c-axis direction, which can further evolve due to photo-stimulated excited states. The excited states are stable enough to meet the timescale of microscopic adsorption equilibrium. Independent of the ultra-low specific surface area of the sorbent (20 m2 g-1 ), the CO adsorption capability can be improved from 0.50 mmol g-1 at the ground state to 1.24 mmol g-1 (0 °C, 1 bar) with the visible light radiation, rather than the photothermal desorption.

Solitary Medium of a Multifunctional Ionic Liquid for Crystallizing Hierarchically Porous Metal-Organic Frameworks.

Hierarchically porous metal-organic frameworks (HP-MOFs), dominating both the micro- and mesoporous regimes, show high potentials in various applications especially those involving bulky biomolecules. The templating method has been proven to be effective in the fabrication of HP-MOFs; however, complicated synthetic systems containing solvents, templates, and additives are frequently employed. Here we report the first example of designing a poly(ethylene glycol)-based alkylammonium and bromide multifunctional ionic liquid (IL) as a solitary medium to construct HP-MOFs, avoiding the involvement of any additional media. Besides the ready solubilization of MOF precursors in the multifunctional IL due to a poly(ethylene glycol) chain as the solubilizer, the ionic moiety facilitates electrostatic interaction to create a templating effect. Hence, UiO-66 with hierarchical porosity has been successfully fabricated, and such a methodology can also be applied to the construction of other HP-MOFs. The resultant HP-UiO-66 is efficient in the encapsulation of bulky biomolecule cytochrome c, and the adsorption capacity is obviously superior to that of the microporous counterpart.

Population pharmacokinetic and pharmacodynamic analysis of rivaroxaban in Chinese patients with non-valvular atrial fibrillation.

Rivaroxaban, a direct factor Xa inhibitor, is widely used for stroke prevention in patients with non-valvular atrial fibrillation (NVAF). The aim of this study was to conduct a population pharmacokinetic-pharmacodynamic (PK-PD) analysis of rivaroxaban in Chinese patients with NVAF to assess ethnic differences and provide model-based precision dosing. A total of 256 rivaroxaban plasma concentrations and 244 prothrombin time (PT) measurements were obtained from 195 Chinese NVAF patients from a prospective clinical trial. The population PK-PD model was developed using nonlinear mixed effects modeling (NONMEM) software. The PK of rivaroxaban was adequately described using a one-compartment model with first-order adsorption and elimination. Estimated glomerular filtration rate (eGFR) was identified as a major covariate for apparent clearance. No single nucleotide polymorphism was identified as a significant covariate. PT exhibited a linear relationship with rivaroxaban concentration. Total bilirubin (TBIL) and eGFR were identified as significant covariates for baseline PT. According to the Monte Carlo simulation, 15 mg for Chinese patients with eGFR ≥50 mL/min and normal liver function yielded an exposure comparable to 20 mg for Caucasian patients. Patients with moderately impaired renal function may require a lower dose of rivaroxaban to avoid overexposure. Moreover, there was an approximate 26% increase in PT levels in patients with TBIL of 34 µmol/L and eGFR of 30 mL/min, which could increase the risk of major bleeding. The established population PK-PD model could inform individualized dosing for Chinese NVAF patients who are administered rivaroxaban.

MiR-873-5p modulates progression of tongue squamous cell carcinoma via targeting SEC11A.

OBJECTIVE: To explore the effect of miR-873-5p on proliferation, apoptosis, migration, and invasion of tongue squamous cell carcinoma (TSCC) by targeting SEC11A. METHODS: Tongue squamous cell carcinoma tissues were collected and performed by qRT-PCR and Western blotting to determine the expression of miR-873-5p and SPC18. SCC9 and CAL-27 cells were transfected and divided into Mock, mimic NC, miR-873-5p mimic, SEC11A, and miR-873-5p mimic + SEC11A groups. Then, a series of experiments including cell count kit 8 (CCK-8), wound healing, Transwell, and flow cytometry were conducted. Besides, Western blotting was used to detect the expression of SPC18 and EGFR pathway-related proteins. RESULTS: MiR-873-5p was downregulated while SPC18 was upregulated in TSCC, and miR-873-5p was negatively correlated with SPC18. Dual luciferase reporter gene assay confirmed SEC11A to be a target of miR-873-5p. Cell proliferation, migration, and invasion of SCC9 and CAL-27 cells in miR-873-5p mimic group were decreased with increased cell apoptosis, presenting with downregulations of SPC18 and EGFR pathway-related proteins, while cells in SEC11A group manifested totally different changes. Moreover, the inhibitory effect of miR-873-5p mimic on TSCC cell growth was abolished by SEC11A overexpression. CONCLUSION: Overexpression of miR-873-5p may suppress cell proliferation, migration, and invasion, but facilitate apoptosis in TSCC via targeting SEC11A.

The functional analysis of the ubiquitin ligase Brl2 in the repair of DNA double-strand breaks.

Mono-ubiquitination of histone H2B plays a critical role in the regulation of gene transcription, DNA replication, and DNA damage repair. In Schizosaccharomyces pombe, Brl2 is an E3 ubiquitin ligase and required for the ubiquitination of H2B at lysine residue 119. Currently, there are few studies related to the function of Brl2 in DNA damage repair. Using camptothecin (CPT) to induce DNA double-strand breaks (DSBs) in S. pombe, we investigated the effect of Brl2 on DSB repair, and found that brl2-null mutants showed greater sensitivity to CPT when compared with wild-type (WT) cells, as well as having a drastically reduced spontaneous recombinant frequency. The fluorescent analysis demonstrated that Brl2 was co-localized with the recombination factor Rad52 at DSBs. Moreover, Brl2 promoted the recruitment of Rad52 to DSBs. Under CPT-induced DSBs, Brl2 was phosphorylated. These findings indicate that Brl2 plays a critical role in DNA homologous recombination and its mediated repair of DSBs.

Porous Liquids Responsive to Light.

A porous liquid is a unique liquid medium that combines the cavity of porous solids with the fluidity of liquids. This special characteristic offers potential in various applications. Here we report a type II photoresponsive porous ionic liquid (PPIL) from dissolving a photoresponsive metal-organic polyhedron (PMOP, constructed from dicopper and azobenzene-containing carboxylate) in a polyethylene-glycol-functionalized bulky ionic liquid (IL). Owing to favorable ion interactions, bulky IL molecules encircle outside PMOP, and the inter cavities are maintained. The azobenzene moieties can be isomerized freely in the PPILs to expose and shelter active sites upon visible and UV light irradiation. Hence, the adsorption capacity of PPILs is controllable by light irradiation, and the change in CO2 uptake is up to 30 % compared to neat IL. This study may inspire the development of new adsorption process regulated by light instead of pressure and temperature swing adsorption.

Reversible Light-Controlled CO Adsorption via Tuning π-Complexation of Cu+ Sites in Azobenzene-Decorated Metal-Organic Frameworks.

Light-responsive adsorbents capture significant attention due to their tailorable performance upon light irradiation. The modulation of such adsorbents is mainly based on weak (physical) interactions caused by steric hindrance while tuning strong interaction with target adsorbates is scarce. Here we report smart π-complexation adsorbents, which can adjust the π-complexation of active sites via light irradiation. A typical metal-organic framework, MIL-101-NH2 , was decorated with azobenzene motifs, and Cu+ as π-complexation active sites were introduced subsequently. The reversible light-induced isomerization of azobenzene regulates the surface electrostatic potentials around Cu+ from -0.038 to 0.008 eV, causing shielding and exposure effects. The alteration of CO uptake is achieved up to 54 % via changing light, while that on MIL-101-NH2 is negligible. This study provides a clue for designing target-specific smart materials to meet the practical stimuli-responsive adsorption demands.

Catalytically Stable Potassium Single-Atom Solid Superbases.

Solid superbases can catalyze diverse reactions under mild conditions, while they suffer from aggregation of basic sites and poor stability during recycling. Here we report a new generation of solid superbases derived from K single atoms (SAs) prepared by a tandem redox strategy. The initial redox reaction takes place between base precursor KNO3 and graphene support, producing K2 O at 400 °C. Further increasing the temperature to 800 °C, the graphene reduces K2 O to K anchored by its vacancies, leading to the generation of K SAs (denoted as K1 /G). The source of basicity in the K1 /G is K SAs, and neighboring single atoms (NSAs) possess superbasicity, which is different from conventional basicity originated from oxygen and nitrogen atoms. Due to the superbasicity as well as high dispersion and anchoring of basic sites, the K1 /G shows excellent catalytic activity and stability in transesterification reaction, which is much superior to the reported catalysts.