ABSTRACT
Cannabis activates the cannabinoid receptor 1 (CB1), which elicits analgesic and emotion regulation benefits, along with adverse effects, via Gi and ß-arrestin signaling pathways. However, the lack of understanding of the mechanism of ß-arrestin-1 (ßarr1) coupling and signaling bias has hindered drug development targeting CB1. Here, we present the high-resolution cryo-electron microscopy structure of CB1-ßarr1 complex bound to the synthetic cannabinoid MDMB-Fubinaca (FUB), revealing notable differences in the transducer pocket and ligand-binding site compared with the Gi protein complex. ßarr1 occupies a wider transducer pocket promoting substantial outward movement of the TM6 and distinctive twin toggle switch rearrangements, whereas FUB adopts a different pose, inserting more deeply than the Gi-coupled state, suggesting the allosteric correlation between the orthosteric binding pocket and the partner protein site. Taken together, our findings unravel the molecular mechanism of signaling bias toward CB1, facilitating the development of CB1 agonists.
Subject(s)
Arrestin , Receptor, Cannabinoid, CB1 , Signal Transduction , Arrestin/metabolism , beta-Arrestin 1/metabolism , beta-Arrestins/metabolism , Cryoelectron Microscopy , Receptor, Cannabinoid, CB1/metabolism , Humans , Animals , Cell LineABSTRACT
Among arthropod vectors, ticks transmit the most diverse human and animal pathogens, leading to an increasing number of new challenges worldwide. Here we sequenced and assembled high-quality genomes of six ixodid tick species and further resequenced 678 tick specimens to understand three key aspects of ticks: genetic diversity, population structure, and pathogen distribution. We explored the genetic basis common to ticks, including heme and hemoglobin digestion, iron metabolism, and reactive oxygen species, and unveiled for the first time that genetic structure and pathogen composition in different tick species are mainly shaped by ecological and geographic factors. We further identified species-specific determinants associated with different host ranges, life cycles, and distributions. The findings of this study are an invaluable resource for research and control of ticks and tick-borne diseases.
Subject(s)
Genetic Variation/genetics , Tick-Borne Diseases/microbiology , Ticks/genetics , Animals , Cell Line , Disease Vectors , Host Specificity/geneticsABSTRACT
Genome-wide association studies (GWAS) have identified rs11672691 at 19q13 associated with aggressive prostate cancer (PCa). Here, we independently confirmed the finding in a cohort of 2,738 PCa patients and discovered the biological mechanism underlying this association. We found an association of the aggressive PCa-associated allele G of rs11672691 with elevated transcript levels of two biologically plausible candidate genes, PCAT19 and CEACAM21, implicated in PCa cell growth and tumor progression. Mechanistically, rs11672691 resides in an enhancer element and alters the binding site of HOXA2, a novel oncogenic transcription factor with prognostic potential in PCa. Remarkably, CRISPR/Cas9-mediated single-nucleotide editing showed the direct effect of rs11672691 on PCAT19 and CEACAM21 expression and PCa cellular aggressive phenotype. Clinical data demonstrated synergistic effects of rs11672691 genotype and PCAT19/CEACAM21 gene expression on PCa prognosis. These results provide a plausible mechanism for rs11672691 associated with aggressive PCa and thus lay the ground work for translating this finding to the clinic.
Subject(s)
Prostatic Neoplasms/genetics , RNA, Long Noncoding/genetics , RNA, Untranslated/genetics , Adult , Alleles , Cell Line, Tumor , Chromosomes, Human, Pair 19/genetics , Cohort Studies , Gene Expression Regulation, Neoplastic/genetics , Gene Frequency/genetics , Genetic Predisposition to Disease/genetics , Genome-Wide Association Study , Genotype , Homeodomain Proteins , Humans , Male , Middle Aged , Polymorphism, Single Nucleotide/genetics , PrognosisABSTRACT
Spatial, momentum and energy separation of electronic spins in condensed-matter systems guides the development of new devices in which spin-polarized current is generated and manipulated1-3. Recent attention on a set of previously overlooked symmetry operations in magnetic materials4 leads to the emergence of a new type of spin splitting, enabling giant and momentum-dependent spin polarization of energy bands on selected antiferromagnets5-10. Despite the ever-growing theoretical predictions, the direct spectroscopic proof of such spin splitting is still lacking. Here we provide solid spectroscopic and computational evidence for the existence of such materials. In the noncoplanar antiferromagnet manganese ditelluride (MnTe2), the in-plane components of spin are found to be antisymmetric about the high-symmetry planes of the Brillouin zone, comprising a plaid-like spin texture in the antiferromagnetic (AFM) ground state. Such an unconventional spin pattern, further found to diminish at the high-temperature paramagnetic state, originates from the intrinsic AFM order instead of spin-orbit coupling (SOC). Our finding demonstrates a new type of quadratic spin texture induced by time-reversal breaking, placing AFM spintronics on a firm basis and paving the way for studying exotic quantum phenomena in related materials.
ABSTRACT
Objects that deform a liquid interface are subject to capillary forces, which can be harnessed to assemble the objects1-4. Once assembled, such structures are generally static. Here we dynamically modulate these forces to move objects in programmable two-dimensional patterns. We 3D-print devices containing channels that trap floating objects using repulsive capillary forces5,6, then move these devices vertically in a water bath. Because the channel cross-sections vary with height, the trapped objects can be steered in two dimensions. The device and interface therefore constitute a simple machine that converts vertical to lateral motion. We design machines that translate, rotate and separate multiple floating objects and that do work on submerged objects through cyclic vertical motion. We combine these elementary machines to make centimetre-scale compound machines that braid micrometre-scale filaments into prescribed topologies, including non-repeating braids. Capillary machines are distinct from mechanical, optical or fluidic micromanipulators in that a meniscus links the object to the machine. Therefore, the channel shapes need only be controlled on the scale of the capillary length (a few millimetres), even when the objects are microscopic. Consequently, such machines can be built quickly and inexpensively. This approach could be used to manipulate micrometre-scale particles or to braid microwires for high-frequency electronics.
ABSTRACT
Although bradykinesia, tremor and rigidity are the hallmark motor defects in patients with Parkinson's disease (PD), patients also experience motor learning impairments and non-motor symptoms such as depression1. The neural circuit basis for these different symptoms of PD are not well understood. Although current treatments are effective for locomotion deficits in PD2,3, therapeutic strategies targeting motor learning deficits and non-motor symptoms are lacking4-6. Here we found that distinct parafascicular (PF) thalamic subpopulations project to caudate putamen (CPu), subthalamic nucleus (STN) and nucleus accumbens (NAc). Whereas PFâCPu and PFâSTN circuits are critical for locomotion and motor learning, respectively, inhibition of the PFâNAc circuit induced a depression-like state. Whereas chemogenetically manipulating CPu-projecting PF neurons led to a long-term restoration of locomotion, optogenetic long-term potentiation (LTP) at PFâSTN synapses restored motor learning behaviour in an acute mouse model of PD. Furthermore, activation of NAc-projecting PF neurons rescued depression-like phenotypes. Further, we identified nicotinic acetylcholine receptors capable of modulating PF circuits to rescue different PD phenotypes. Thus, targeting PF thalamic circuits may be an effective strategy for treating motor and non-motor deficits in PD.
Subject(s)
Affect , Motor Skills , Neural Pathways , Parkinson Disease , Thalamus , Animals , Disease Models, Animal , Learning , Locomotion , Long-Term Potentiation , Mice , Neurons/physiology , Nucleus Accumbens , Optogenetics , Parkinson Disease/physiopathology , Parkinson Disease/psychology , Parkinson Disease/therapy , Putamen , Receptors, Nicotinic , Subthalamic Nucleus , Synapses , Thalamus/cytology , Thalamus/pathologyABSTRACT
The deep population history of East Asia remains poorly understood owing to a lack of ancient DNA data and sparse sampling of present-day people1,2. Here we report genome-wide data from 166 East Asian individuals dating to between 6000 BC and AD 1000 and 46 present-day groups. Hunter-gatherers from Japan, the Amur River Basin, and people of Neolithic and Iron Age Taiwan and the Tibetan Plateau are linked by a deeply splitting lineage that probably reflects a coastal migration during the Late Pleistocene epoch. We also follow expansions during the subsequent Holocene epoch from four regions. First, hunter-gatherers from Mongolia and the Amur River Basin have ancestry shared by individuals who speak Mongolic and Tungusic languages, but do not carry ancestry characteristic of farmers from the West Liao River region (around 3000 BC), which contradicts theories that the expansion of these farmers spread the Mongolic and Tungusic proto-languages. Second, farmers from the Yellow River Basin (around 3000 BC) probably spread Sino-Tibetan languages, as their ancestry dispersed both to Tibet-where it forms approximately 84% of the gene pool in some groups-and to the Central Plain, where it has contributed around 59-84% to modern Han Chinese groups. Third, people from Taiwan from around 1300 BC to AD 800 derived approximately 75% of their ancestry from a lineage that is widespread in modern individuals who speak Austronesian, Tai-Kadai and Austroasiatic languages, and that we hypothesize derives from farmers of the Yangtze River Valley. Ancient people from Taiwan also derived about 25% of their ancestry from a northern lineage that is related to, but different from, farmers of the Yellow River Basin, which suggests an additional north-to-south expansion. Fourth, ancestry from Yamnaya Steppe pastoralists arrived in western Mongolia after around 3000 BC but was displaced by previously established lineages even while it persisted in western China, as would be expected if this ancestry was associated with the spread of proto-Tocharian Indo-European languages. Two later gene flows affected western Mongolia: migrants after around 2000 BC with Yamnaya and European farmer ancestry, and episodic influences of later groups with ancestry from Turan.
Subject(s)
Genome, Human/genetics , Genomics , Human Migration/history , China , Crop Production/history , Female , Haplotypes/genetics , History, Ancient , Humans , Japan , Language/history , Male , Mongolia , Nepal , Oryza , Polymorphism, Single Nucleotide/genetics , Siberia , TaiwanABSTRACT
The ongoing outbreak of viral pneumonia in China and across the world is associated with a new coronavirus, SARS-CoV-21. This outbreak has been tentatively associated with a seafood market in Wuhan, China, where the sale of wild animals may be the source of zoonotic infection2. Although bats are probable reservoir hosts for SARS-CoV-2, the identity of any intermediate host that may have facilitated transfer to humans is unknown. Here we report the identification of SARS-CoV-2-related coronaviruses in Malayan pangolins (Manis javanica) seized in anti-smuggling operations in southern China. Metagenomic sequencing identified pangolin-associated coronaviruses that belong to two sub-lineages of SARS-CoV-2-related coronaviruses, including one that exhibits strong similarity in the receptor-binding domain to SARS-CoV-2. The discovery of multiple lineages of pangolin coronavirus and their similarity to SARS-CoV-2 suggests that pangolins should be considered as possible hosts in the emergence of new coronaviruses and should be removed from wet markets to prevent zoonotic transmission.
Subject(s)
Betacoronavirus/genetics , Betacoronavirus/isolation & purification , Eutheria/virology , Evolution, Molecular , Genome, Viral/genetics , Sequence Homology, Nucleic Acid , Amino Acid Sequence , Animals , Betacoronavirus/chemistry , Betacoronavirus/classification , COVID-19 , China/epidemiology , Chiroptera/virology , Coronavirus Infections/epidemiology , Coronavirus Infections/transmission , Coronavirus Infections/virology , Disease Reservoirs/virology , Genomics , Humans , Malaysia , Pandemics , Phylogeny , Pneumonia, Viral/epidemiology , Pneumonia, Viral/transmission , Pneumonia, Viral/virology , Recombination, Genetic , SARS-CoV-2 , Sequence Alignment , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Zoonoses/virologyABSTRACT
Chromosome instability (CIN) is frequently observed in many tumors. The breakage-fusion-bridge (BFB) cycle has been proposed to be one of the main drivers of CIN during tumorigenesis and tumor evolution. However, the detailed mechanism for the individual steps of the BFB cycle warrants further investigation. Here, we demonstrate that a nuclease-dead Cas9 (dCas9) coupled with a telomere-specific single-guide RNA (sgTelo) can be used to model the BFB cycle. First, we show that targeting dCas9 to telomeres using sgTelo impedes DNA replication at telomeres and induces a pronounced increase of replication stress and DNA damage. Using Single-Molecule Telomere Assay via Optical Mapping (SMTA-OM), we investigate the genome-wide features of telomeres in the dCas9/sgTelo cells and observe a dramatic increase of chromosome end fusions, including fusion/ITS+ and fusion/ITS-. Consistently, we also observe an increase in the formation of dicentric chromosomes, anaphase bridges, and intercellular telomeric chromosome bridges (ITCBs). Utilizing the dCas9/sgTelo system, we uncover many interesting molecular and structural features of the ITCB and demonstrate that multiple DNA repair pathways are implicated in the formation of ITCBs. Our studies shed new light on the molecular mechanisms of the BFB cycle, which will advance our understanding of tumorigenesis, tumor evolution, and drug resistance.
Subject(s)
CRISPR-Cas Systems , Chromosomal Instability , DNA Replication , Telomere , Humans , Telomere/genetics , DNA Replication/genetics , DNA Damage , RNA, Guide, CRISPR-Cas Systems/genetics , CRISPR-Associated Protein 9/metabolism , CRISPR-Associated Protein 9/geneticsABSTRACT
Rewiring of redox metabolism has a profound impact on tumor development, but how the cellular heterogeneity of redox balance affects leukemogenesis remains unknown. To precisely characterize the dynamic change in redox metabolism in vivo, we developed a bright genetically encoded biosensor for H2O2 (named HyPerion) and tracked the redox state of leukemic cells in situ in a transgenic sensor mouse. A H2O2-low (HyPerion-low) subset of acute myeloid leukemia (AML) cells was enriched with leukemia-initiating cells, which were endowed with high colony-forming ability, potent drug resistance, endosteal rather than vascular localization, and short survival. Significantly high expression of malic enzymes, including ME1/3, accounted for nicotinamide adenine dinucleotide phosphate (NADPH) production and the subsequent low abundance of H2O2. Deletion of malic enzymes decreased the population size of leukemia-initiating cells and impaired their leukemogenic capacity and drug resistance. In summary, by establishing an in vivo redox monitoring tool at single-cell resolution, this work reveals a critical role of redox metabolism in leukemogenesis and a potential therapeutic target.
Subject(s)
Hydrogen Peroxide , Leukemia, Myeloid, Acute , Mice , Animals , Leukemia, Myeloid, Acute/drug therapy , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/metabolism , Oxidation-Reduction , Mice, Transgenic , Drug Resistance, Neoplasm/geneticsABSTRACT
Abscisic acid (ABA) is involved in salt and drought stress responses, but the underlying molecular mechanism remains unclear. Here, we demonstrated that the overexpression of MdMYB44-like, an R2R3-MYB transcription factor, significantly increases the salt and drought tolerance of transgenic apples and Arabidopsis. MdMYB44-like inhibits the transcription of MdPP2CA, which encodes a type 2C protein phosphatase that acts as a negative regulator in the ABA response, thereby enhancing ABA signaling-mediated salt and drought tolerance. Furthermore, we found that MdMYB44-like and MdPYL8, an ABA receptor, form a protein complex that further enhances the transcriptional inhibition of the MdPP2CA promoter by MdMYB44-like. Significantly, we discovered that MdPP2CA can interfere with the physical association between MdMYB44-like and MdPYL8 in the presence of ABA, partially blocking the inhibitory effect of the MdMYB44-like-MdPYL8 complex on the MdPP2CA promoter. Thus, MdMYB44-like, MdPYL8, and MdPP2CA form a regulatory loop that tightly modulates ABA signaling homeostasis under salt and drought stress. Our data reveal that MdMYB44-like precisely modulates ABA-mediated salt and drought tolerance in apples through the MdPYL8-MdPP2CA module.
Subject(s)
Arabidopsis , Malus , Malus/genetics , Malus/metabolism , Drought Resistance , Plant Proteins/genetics , Plant Proteins/metabolism , Plants, Genetically Modified/metabolism , Sodium Chloride/pharmacology , Arabidopsis/metabolism , Abscisic Acid/metabolism , Droughts , Gene Expression Regulation, Plant , Stress, PhysiologicalABSTRACT
BACKGROUND AND AIMS: The common characteristics of alcohol-associated liver injury (ALI) include abnormal liver function, infiltration of inflammatory cells, and generation of oxidative stress. The gastrin-releasing peptide receptor (GRPR) is activated by its neuropeptide ligand, gastrin-releasing peptide (GRP). GRP/GRPR appears to induce the production of cytokines in immune cells and promotes neutrophil migration. However, the effects of GRP/GRPR in ALI are unknown. APPROACH AND RESULTS: We found high GRPR expression in the liver of patients with alcohol-associated steatohepatitis and increased pro-GRP levels in peripheral blood mononuclear cells of these patients compared with that of the control. Increased expression of GRP may be associated with histone H3 lysine 27 acetylation induced by alcohol, which promotes the expression of GRP and then GRPR binding. Grpr-/- and Grprflox/floxLysMCre mice alleviated ethanol-induced liver injury with relieved steatosis, lower serum alanine aminotransferase, aspartate aminotransferase, triglycerides, malondialdehyde, and superoxide dismutase levels, reduced neutrophil influx, and decreased expression and release of inflammatory cytokines and chemokines. Conversely, the overexpression of GRPR showed opposite effects. The pro-inflammatory and oxidative stress roles of GRPR might be dependent on IRF1-mediated Caspase-1 inflammasome and NOX2-dependent reactive oxygen species pathway, respectively. In addition, we verified the therapeutic and preventive effects of RH-1402, a novel GRPR antagonist, for ALI. CONCLUSIONS: A knockout or antagonist of GRPR during excess alcohol intake could have anti-inflammatory and antioxidative roles, as well as provide a platform for histone modification-based therapy for ALI.
Subject(s)
Inflammasomes , Receptors, Bombesin , Humans , Mice , Animals , Receptors, Bombesin/metabolism , Inflammasomes/metabolism , Reactive Oxygen Species/metabolism , Caspase 1/metabolism , Leukocytes, Mononuclear , Gastrin-Releasing Peptide/metabolism , Ethanol , Liver/metabolism , Cytokines/metabolism , Interferon Regulatory Factor-1/metabolismABSTRACT
Hepatocellular carcinoma (HCC) is a cancer with high morbidity and mortality. Studies have shown that histone modification plays an important regulatory role in the occurrence and development of HCC. However, the specific regulatory effects of histone modifications on gene expression in HCC are still unclear. This study focuses on HepG2 cell lines and hepatocyte cell lines. First, the distribution of histone modification signals in the two cell lines was calculated and analyzed. Then, using the random forest algorithm, we analyzed the effects of different histone modifications and their modified regions on gene expression in the two cell lines, four key histone modifications (H3K36me3, H3K4me3, H3K79me2, and H3K9ac) and five key regions that co-regulate gene expression were obtained. Subsequently, target genes regulated by key histone modifications in key regions were screened. Combined with clinical data, Cox regression analysis and Kaplan-Meier survival analysis were performed on the target genes, and four key target genes (CBX2, CEBPZOS, LDHA, and UMPS) related to prognosis were identified. Finally, through immune infiltration analysis and drug sensitivity analysis of key target genes, the potential role of key target genes in HCC was confirmed. Our results provide a theoretical basis for exploring the occurrence of HCC and propose potential biomarkers associated with histone modifications, which may be potential drug targets for the clinical treatment of HCC.
Subject(s)
Carcinoma, Hepatocellular , Gene Expression Regulation, Neoplastic , Histone Code , Histones , Liver Neoplasms , Humans , Carcinoma, Hepatocellular/genetics , Carcinoma, Hepatocellular/metabolism , Carcinoma, Hepatocellular/pathology , Liver Neoplasms/genetics , Liver Neoplasms/metabolism , Liver Neoplasms/pathology , Hep G2 Cells , Histone Code/genetics , Histones/metabolism , Histones/genetics , Prognosis , Kaplan-Meier EstimateABSTRACT
In the global health community, colorectal cancer (CRC) is a major concern, with a high rate of incidence. Mono-ADP-ribosylation (MARylation) is a type of epigenetics and recognized as one of the causes of CRC development and progression. Although the modification level and target proteins in CRC remain unclear, it has been found that MARylation of arginine-117 of histone 3 (H3R117) promotes the proliferation, upregulates methylation of tumor suppressor gene, and is tightly associated with the metabolic processes in LoVo cells. Lipid metabolism disorder is involved in the development of CRC at the early stage. Our study revealed that MARylation of H3R117 of the LoVo cells modulated lipid metabolism, increased cholesterol synthesis, promoted lipid raft (LR) protein IGF-1R distribution, and inhibited cell apoptosis through IGFBP1. In addition, bioinformatics analyses revealed that IGFBP1 promoter was hypermethylated in CRC when compared to that in normal tissues. Moreover, H3R117 MARylation upregulated the methylation of IGFBP1 promoter through histone H3 citrullination (H3cit) by increasing the H3K9me2, heterochromatin protein1 (HP1), and DNA methyltransferase 1 (DNMT1) enrichment of IGFBP1 promoter. Accordingly, IGFBP1 may function as a tumor suppressor gene, while H3R117 MARylation may promote CRC development. Our study findings enrich the available data on epigenetics of CRC and provide a new idea and experimental basis for H3R117 MARylation as a target in CRC treatment.
ABSTRACT
The Wnt/ß-catenin pathway is critical to maintaining cell fate decisions. Recent study showed that liquid-liquid-phase separation (LLPS) of Axin organized the ß-catenin destruction complex condensates in a normal cellular state. Mutations inactivating the APC gene are found in approximately 80% of all human colorectal cancer (CRC). However, the molecular mechanism of the formation of ß-catenin destruction complex condensates organized by Axin phase separation and how APC mutations impact the condensates are still unclear. Here, we report that the ß-catenin destruction complex, which is constructed by Axin, was assembled condensates via a phase separation process in CRC cells. The key role of wild-type APC is to stabilize destruction complex condensates. Surprisingly, truncated APC did not affect the formation of condensates, and GSK 3ß and CK1α were unsuccessfully recruited, preventing ß-catenin phosphorylation and resulting in accumulation in the cytoplasm of CRCs. Besides, we propose that the phase separation ability of Axin participates in the nucleus translocation of ß-catenin and be incorporated and concentrated into transcriptional condensates, affecting the transcriptional activity of Wnt signaling pathway.
Subject(s)
Axin Signaling Complex , beta Catenin , Humans , Axin Signaling Complex/genetics , Axin Protein/genetics , Axin Protein/metabolism , beta Catenin/genetics , beta Catenin/metabolism , Phase Separation , Mutation/genetics , Wnt Signaling Pathway/genetics , Adenomatous Polyposis Coli Protein/genetics , Adenomatous Polyposis Coli Protein/metabolismABSTRACT
To date, it remains challenging to precisely and efficiently construct structurally intriguing polycarbocycles with densely packed stereocenters in organic synthesis. Niduterpenoid B, a naturally occurring ERα inhibitor, exemplifies this complexity with its intricate polycyclic network comprising 5 cyclopentane and 1 cyclopropane rings, featuring 13 contiguous stereocenters, including 4 all-carbon quaternary centers. In this work, we describe the first total synthesis of niduterpenoid B using a structural reorganization strategy. Key features include the following: (1) an efficient methoxy-controlled cascade reaction that precisely forges a highly functionalized tetraquinane (A-D rings) bearing sterically hindered contiguous quaternary stereocenters; (2) a rhodium-catalyzed [1 + 2] cycloaddition that facilitates the construction of a strained 3/5 bicycle (E-F rings) angularly fused with ring D.
ABSTRACT
Electrosynthesis of H2O2 provides an environmentally friendly alternative to the traditional anthraquinone method employed in industry, but suffers from impurities and restricted yield rate and concentration of H2O2. Herein, we demonstrated a Ni-phthalocyanine-based covalent-organic framework (COF, denoted as BBL-PcNi) with a higher inherent conductivity of 1.14 × 10-5 S m-1, which exhibited an ultrahigh current density of 530 mA cm-2 with a Faradaic efficiency (H2O2) of â¼100% at a low cell voltage of 3.5 V. Notably, this high level of performance is maintained over a continuous operation of 200 h without noticeable degradation. When integrated into a scale-up membrane electrode assembly electrolyzer and operated at â¼3300 mA at a very low cell voltage of 2 V, BBL-PcNi continuously yielded a pure H2O2 solution with medical-grade concentration (3.5 wt %), which is at least 3.5 times higher than previously reported catalysts and 1.5 times the output of the traditional anthraquinone process. A mechanistic study revealed that enhancing the π-conjugation to reduce the band gap of the molecular catalytic sites integrated into a COF is more effective to enhance its inherent electron transport ability, thereby significantly improving the electrocatalytic performance for H2O2 generation.
ABSTRACT
High-purity CO2 rather than dilute CO2 (15 vol %, CO2/N2/O2 = 15:80:5, v/v/v) similar to the flue gas is currently used as the feedstock for the electroreduction of CO2, and the liquid products are usually mixed up with the cathode electrolyte, resulting in high product separation costs. In this work, we showed that a microporous conductive Bi-based metal-organic framework (Bi-HHTP, HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) can not only efficiently capture CO2 from the dilute CO2 under high humidity but also catalyze the electroreduction of the adsorbed CO2 into formic acid with a high current density of 80 mA cm-2 and a Faradaic efficiency of 90% at a very low cell voltage of 2.6 V. Importantly, the performance in a dilute CO2 atmosphere was close to that under a high-purity CO2 atmosphere. This is the first catalyst that can maintain exceptional eCO2RR performance in the presence of both O2 and N2. Moreover, by using dilute CO2 as the feedstock, a 1 cm-2 working electrode coating with Bi-HHTP can continuously produce a 200 mM formic acid aqueous solution with a relative purity of 100% for at least 30 h in a membrane electrode assembly (MEA) electrolyzer. The product does not contain electrolytes, and such a highly concentrated and pure formic acid aqueous solution can be directly used as an electrolyte for formic acid fuel cells. Comprehensive studies revealed that such a high performance might be ascribed to the CO2 capture ability of the micropores on Bi-HHTP and the lower Gibbs free energy of formation of the key intermediate *OCHO on the open Bi sites.
ABSTRACT
It is crucial to achieve continuous production of highly concentrated and pure C2 chemicals through the electrochemical CO2 reduction reaction (eCO2RR) for artificial carbon cycling, yet it has remained unattainable until now. Despite one-pot tandem catalysis (dividing the eCO2RR to C2 into two catalytical reactions of CO2 to CO and CO to C2) offering the potential for significantly enhancing reaction efficiency, its mechanism remains unclear and its performance is unsatisfactory. Herein, we selected different CO2-to-CO catalysts and CO-to-acetate catalysts to construct several tandem catalytic systems for the eCO2RR to acetic acid. Among them, a tandem catalytic system comprising a covalent organic framework (PcNi-DMTP) and a metal-organic framework (MAF-2) as CO2-to-CO and CO-to-acetate catalysts, respectively, exhibited a faradaic efficiency of 51.2% with a current density of 410 mA cm-2 and an ultrahigh acetate yield rate of 2.72 mmol m-2 s-1 under neutral conditions. After electrolysis for 200 h, 1 cm-2 working electrode can continuously produce 20 mM acetic acid aqueous solution with a relative purity of 95+%. Comprehensive studies revealed that the performance of tandem catalysts is influenced not only by the CO supply-demand relationship and electron competition between the two catalytic processes in the one-pot tandem system but also by the performance of the CO-to-C2 catalyst under diluted CO conditions.
ABSTRACT
Construction of mesoporous frameworks by noncovalent bonding still remains a great challenge. Here, we report a micelle-directed nanocluster modular self-assembly approach to synthesize a novel type of two-dimensional (2-D) hydrogen-bonded mesoporous frameworks (HMFs) for the first time based on nanoscale cluster units (1.0-3.0 nm in size). In this 2-D structure, a mesoporous cluster plate with â¼100 nm in thickness and several micrometers in size can be stably formed into uniform hexagonal arrays. Meanwhile, such a porous plate consists of several (3-4) dozens of layers of ultrathin mesoporous cluster nanosheets. The size of the mesopores can be precisely controlled from 11.6 to 18.5 nm by utilizing the amphiphilic diblock copolymer micelles with tunable block lengths. Additionally, the pore configuration of the HMFs can be changed from spherical to cylindrical by manipulating the concentration of the micelles. As a general approach, various new HMFs have been achieved successfully via a modular self-assembly of nanoclusters with switchable configurations (nanoring, Keggin-type, and cubane-like) and components (titanium-oxo, polyoxometalate, and organometallic clusters). As a demonstration, the titanium-oxo cluster-based HMFs show efficient photocatalytic activity for hydrogen evolution (3.6 mmol g-1h-1), with a conversion rate about 2 times higher than that of the unassembled titanium-oxo clusters (1.5 mmol g-1h-1). This demonstrates that HMFs exhibited enhanced photocatalytic activity compared with unassembled titanium-oxo clusters units.