Ethane/Ethylene Separations in Flexible Diamondoid Coordination Networks via an Ethane-Induced Gate-Opening Mechanism.

Separating ethane (C2H6) from ethylene (C2H4) is an essential and energy-intensive process in the chemical industry. Here, we report two flexible diamondoid coordination networks, X-dia-1-Ni and X-dia-1-Ni0.89Co0.11, that exhibit gate-opening between narrow-pore (NP) and large-pore (LP) phases for C2H6, but not for C2H4. X-dia-1-Ni0.89Co0.11 thereby exhibited a type F-IV isotherm at 273 K with no C2H6 uptake and a high uptake (111 cm3 g-1, 1 atm) for the NP and LP phases, respectively. Conversely, the LP phase exhibited a low uptake of C2H4 (12.2 cm3 g-1). This C2H6/C2H4 uptake ratio of 9.1 for X-dia-1-Ni0.89Co0.11 far surpassed those of previously reported physisorbents, many of which are C2H4-selective. In situ variable-pressure X-ray diffraction and modeling studies provided insight into the abrupt C2H6-induced structural NP to LP transformation. The promise of pure gas isotherms and, more generally, flexible coordination networks for gas separations was validated by dynamic breakthrough studies, which afforded high-purity (99.9%) C2H4 in one step.

Ligand Defect-Induced Active Sites in Ni-MOF-74 for Efficient Photocatalytic CO2 Reduction to CO.

The conversion of CO2 into valuable carbon-based products using clean and renewable solar energy has been a significant challenge in photocatalysis. It is of paramount importance to develop efficient photocatalysts for the catalytic conversion of CO2 using visible light. In this study, the Ni-MOF-74 material is successfully modified to achieve a highly porous structure (Ni-74-Am) through temperature and solvent modulation. Compared to the original Ni-MOF-74, Ni-74-Am contains more unsaturated Ni active sites resulting from defects, thereby enhancing the performance of CO2 photocatalytic conversion. Remarkably, Ni-74-Am exhibits outstanding photocatalytic performance, with a CO generation rate of 1380 µmol g-1 h-1 and 94% CO selectivity under visible light, significantly surpassing the majority of MOF-based photocatalysts reported to date. Furthermore, experimental characterizations reveal that Ni-74-Am has significantly higher efficiency of photogenerated electron-hole separation and faster carrier migration rate for photocatalytic CO2 reduction. This work enriches the design and application of defective MOFs and provides new insights into the design of MOF-based photocatalysts for renewable energy and environmental sustainability. The findings of this study hold significant promise for developing efficient photocatalysts for CO2 reduction under visible-light conditions.

Identifying the Role of Surface Hydroxyl on FeOCl in Bridging Electron Transfer toward Efficient Persulfate Activation.

FeOCl is a highly effective candidate material for advanced oxidation process (AOP) catalysts, but there remain enormous uncertainties about the essence of its outstanding activity. Herein, we clearly elucidate the mechanism involved in the FeOCl-catalyzed perdisulfate (PDS) activation, and the role of surface hydroxyls in bridging the electron transfer between Fe sites and PDS onto the FeOCl/H2O interface is highlighted. ATR-FTIR and Raman analyses reveal that phosphate could suppress the activity of FeOCl via substituting its surface hydroxyls, demonstrating the essential role of hydroxyl in PDS activation. By the use of X-ray absorption fine structure and density functional theory calculations, we found that the polar surface of FeOCl experienced prominent hydrolyzation, which enriched abundant electrons within the microarea around the Fe site, leading to a stronger attraction between FeOCl and PDS. As a result, PDS adsorption onto the FeOCl/H2O interface was obviously enhanced, the bond length of O-O in adsorbed PDS was lengthened, and the electron transfer from Fe atoms to O-O was also promoted. This work proposed a new strategy for PDS-based AOP development and a hint of building efficient heterogeneous AOP catalysts via regulating the hydroxylation of active sites.

Extracellular electron transfer for aerobic denitrification mediated by the bioelectric catalytic system with zero-carbon source.

The slow rate of electron transfer and the large consumption of carbon sources are technical bottlenecks in the biological treatment of wastewater. Here, we first proposed to domesticate aerobic denitrifying bacteria (ADB) from heterotrophic to autotrophic by electricity (0.6 V) under zero organic carbon source conditions, to accelerate electron transfer and shorten hydraulic retention time (HRT) while increasing the biodegradation rate. Then we investigated the extracellular electron transfer (EET) mechanism mediated by this process, and additionally examined the integrated nitrogen removal efficiency of this system with composite pollution. It was demonstrated that compared with the traditional membrane bioreactor (MBR), the BEC displayed higher nitrogen removal efficiency. Especially at C/N = 0, the BEC exhibited a NO3--N removal rate of 95.42 ± 2.71 % for 4 h, which was about 6.5 times higher than that of the MBR. Under the compound pollution condition, the BEC still maintained high NO3--N and tetracycline removal (94.52 ± 2.01 % and 91.50 ± 0.001 %), greatly superior to the MBR (10.64 ± 2.01 % and 12.00 ± 0.019 %). In addition, in-situ electrochemical tests showed that the nitrate in the BEC could be directly converted to N2 by reduction using electrons from the cathode, which was successfully demonstrated as a terminal electron acceptor.

Linking nuclear matrix-localized PIAS1 to chromatin SUMOylation via direct binding of histones H3 and H2A.Z.

As a conserved posttranslational modification, SUMOylation has been shown to play important roles in chromatin-related biological processes including transcription. However, how the SUMOylation machinery associates with chromatin is not clear. Here, we present evidence that multiple SUMOylation machinery components, including SUMO E1 proteins SAE1 and SAE2 and the PIAS (protein inhibitor of activated STAT) family SUMO E3 ligases, are primarily associated with the nuclear matrix rather than with chromatin. We show using nuclease digestion that all PIAS family proteins maintain nuclear matrix association in the absence of chromatin. Of importance, we identify multiple histones including H3 and H2A.Z as directly interacting with PIAS1 and demonstrate that this interaction requires the PIAS1 SAP (SAF-A/B, Acinus, and PIAS) domain. We demonstrate that PIAS1 promotes SUMOylation of histones H3 and H2B in both a SAP domain- and an E3 ligase activity-dependent manner. Furthermore, we show that PIAS1 binds to heat shock-induced genes and represses their expression and that this function also requires the SAP domain. Altogether, our study reveals for the first time the nuclear matrix as the compartment most enriched in SUMO E1 and PIAS family E3 ligases. Our finding that PIAS1 interacts directly with histone proteins also suggests a molecular mechanism as to how nuclear matrix-associated PIAS1 is able to regulate transcription and other chromatin-related processes.

An acetylation-enhanced interaction between transcription factor Sox2 and the steroid receptor coactivators facilitates Sox2 transcriptional activity and function.

SRY-box 2 (Sox2) is a transcription factor with critical roles in maintaining embryonic stem (ES) cell and adult stem cell functions and in tumorigenesis. However, how Sox2 exerts its transcriptional function remains unclear. Here, we used an in vitro protein-protein interaction assay to discover transcriptional regulators for ES cell core transcription factors (Oct4, Sox2, Klf4, and c-Myc) and identified members of the steroid receptor coactivators (SRCs) as Sox2-specific interacting proteins. The SRC family coactivators have broad roles in transcriptional regulation, but it is unknown whether they also serve as Sox2 coactivators. We demonstrated that these proteins facilitate Sox2 transcriptional activity and act synergistically with p300. Furthermore, we uncovered an acetylation-enhanced interaction between Sox2 and SRC-2/3, but not SRC-1, demonstrating it is Sox2 acetylation that promotes the interaction. We identified putative Sox2 acetylation sites required for acetylation-enhanced interaction between Sox2 and SRC-3 and demonstrated that acetylation on these sites contributes to Sox2 transcriptional activity and recruitment of SRC-3. We showed that activation domains 1 and 2 of SRC-3 both display a preferential binding to acetylated Sox2. Finally, functional analyses in mouse ES cells demonstrated that knockdown of SRC-2/3 but not SRC-1 in mouse ES cells significantly downregulates the transcriptional activities of various Sox2 target genes and impairs ES cell stemness. Taken together, we identify specific SRC family proteins as novel Sox2 coactivators and uncover the role of Sox2 acetylation in promoting coactivator recruitment and Sox2 transcriptional function.

Insights into the role of strontium in catalytic combustion of toluene over La1-xSrxCoO3 perovskite catalysts.

A series of LaCoO3 perovskite catalysts substituted by Sr in the A site (La1-xSrxCoO3) were prepared via a facile sol-gel method. The catalytic activity of these perovskite catalysts for the deep oxidation of toluene was evaluated. It was found that Sr substitution significantly enhanced the redox properties, the concentration of oxygen vacancies, and surface Co3+ active species via an electron interaction between Sr and Co from the results of Raman spectroscopy, H2-TPR (temperature programmed reduction), O2-TPD (temperature programmed desorption) and XPS (X-ray photoelectron spectroscopy). Typically, La0.82Sr0.18CoO3 (L0.82S0.18C) exhibited a superior catalytic performance among these samples owing to its best reducibility and highest number of active species. Kinetic analysis further revealed a higher reaction rate (5.1 × 10-7 mol g-1·s-1 at 210 °C) and a lower apparent activation energy (69.1 kJ mol-1) for toluene oxidation on the L0.82S0.18C sample in comparison to those on the others. In situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) confirmed the easy desorption of immediate products from the surface of the L0.82S0.18C sample, which could be responsible for its remarkable performance. These results could provide an efficient strategy for promoting the toluene oxidation through finely tuning the reducibility and surface active phase of the catalysts.

Constructing the vacancies and defects by hemp stem core alkali extraction residue biochar for highly effective removal of heavy metal ions.

Defects and vacancies are the essential reasons for the removal of heavy metal ions from wastewater by low-cost biochar materials. This study aimed to use chemically activated hemp stem core alkali extraction residue biochar as an adsorbent to remove nickel (Ni) and copper (Cu) ions from the simulated waste liquid. A large number of defects and vacancies were introduced into the pyrolysis process to study the efficient removal of heavy metal ions Cu and Ni by hemp rod biomass carbon material (HSR-BC) with different carbon base mass ratios and temperatures. The specific surface area of the prepared hemp rod active biochar was highly correlated with the aperture and carbon base ratio and temperature, and reached the maximum value (1429 m2/g) at 600 °C with the ratio of carbon to base (1:3.5). The removal rates of heavy metals Ni(II) and Cu(II) were as high as 94.25% and 99.54%, respectively, and the adsorption capacities were up to 7.85 mg/g and 24.88 mg/g. The adsorption isotherm follows the Langmuir equation and chemo-adsorption was the main adsorption process. Comparing the surface defects and vacancies of biochar materials before and after adsorption showed that the defects of sp-C and oxygen vacancies produced on the edge of the carbon were the main active sites of the biochar material, an amount of carbon defects would become an anchor site for the Lewis acidic groups, the defective acid site strengthened the electron transfer between the functional group and the Ni(II)/Cu(II), promoted the strong cooperation of Ni(II)/Cu(II) ions with -COOH group to enable efficient and rapid adsorption removal. In addition, a large number of carbon-deficient structures could quickly anchor the Ni(II)/Cu(II) due to their local electron deficiency state, which was difficult to desorb. This study provided an in-depth understanding and guidance for the development of low-cost biochar materials with excellent removal performance of heavy metal ions.

Cerasome-based gold-nanoshell encapsulating L-menthol for ultrasound contrast imaging and photothermal therapy of cancer.

Various nanoformulations of perfluorocarbon have been developed thus far, to achieve ultrasound imaging of tumors and tumor-targeted therapy. However, their application has been greatly limited by their short sonographic duration and large size distribution. A novel theranostic agent was constructed based on gold nanoshell cerasome-encapsulated L-menthol (GNC-LM). Owing to the sustained and controllable generation of L-menthol bubbles under near-infrared laser irradiation, GNC-LM showed good performance in contrast enhancement of ultrasound imaging in vivo. GNC-LM could be imaged for 30 min, which is much longer than the imaging time of SonoVue (commercially used microbubbles). Moreover, photothermal therapy (PTT) based on the light-to-heat conversion of the nanosystem effectively ablated the tumor. Our study demonstrated the promising potential of the obtained GNC-LM to serve as a therapeutic nanoprobe for ultrasound contrast imaging and PTT of tumors.

The Influence of the Charge Compensating Anions of Layered Double Hydroxides (LDHs) in LDH-NS/Graphene Oxide Nanohybrid for CO2 Capture.

In this paper, the influence of charge compensating anions of Layered double hydroxides (LDHs) in the LDH-NS/GO nanohybrid for carbon dioxide capture was systematically investigated. The four kinds of different charge compensating anion intercalated LDH were exfoliated and the LDH and Graphene oxide (GO) nanohybrids were synthesized by "exfoliation-self-assembly" method. In this contribution, the CO2 capture capacity of LDH was improved by introducing of GO. And the calcination and adsorption conditions were tested, which proved that the LDH-NS/GO nanohybrids can be used in a wide temperature range for carbon dioxide capture, and the appropriate calcination temperature is 400 °C. Furthermore, the LDH-NS/GO nanohybrids also have a good multiple adsorption/desorption stability, which is vital for practical application.

Hydrogel-Based Interfacial Solar-Driven Evaporation: Essentials and Trails.

Hydrogel-based interfacial solar-driven evaporation (ISDE) gives full play to the highly adjustable physical and chemical properties of hydrogel, which endows ISDE systems with excellent evaporation performance, anti-pollution properties, and mechanical behavior, making it more promising for applications in seawater desalination and wastewater treatment. This review systematically introduces the latest advances in hydrogel-based ISDE systems from three aspects: the required properties, the preparation methods, and the role played in application scenarios of hydrogels used in ISDE. Additionally, we also discuss the remaining challenges and potential opportunities in hydrogel-based ISDE systems. By summarizing the latest research progress, we hope that researchers in related fields have some insight into the unique advantages of hydrogels in the ISDE field and contribute our efforts so that ISDE technology reaches the finishing line of practical application on the hydrogel track.

Oxygen vacancy induction strategy to regulate the evolution of valence- and free-electrons for boosting visible photodegradation of tetracycline hydrochloride.

The generation, migration and reaction paths of electrons are the key steps for photodegradation of pollutants. However, efficient operation of the above pathways is still challenging. Herein, by strong coordination and slow pyrolysis, we constructed a narrow band Zn-Mn bimetallic photoactive core-shell material (Mn@Zn-N-C, Eg = 3.38 eV) with abundant oxygen vacancies for enhancing the above electronic paths. The photodegradation experiments of tetracycline hydrochloride (TCH) showed that the formation and transfer of vacancy-induced free electrons in the synthesized Mn@Zn-N-C was the key to improve the photocatalytic activity. The DFT calculation results revealed that the photogenerated electrons can transfer along the Mn-O-Zn bridge in Mn@Zn-N-C, and promote the formation of MnIV, which directly capture the free electrons and reset itself to MnII site. In this case, the introduction of Mn would enhance the separation of h+ and e-. The adjacent vacancies and defects then also trapped the above free electrons and hinder the recombination of photogenerated carriers. Simultaneously, the localized valence electron transfer between the above redox pairs (Mn4+/Mn2+ and Zn2+/Zn0) also promoted the long-term stability of the photocatalytic process. In summary, using vacancy induction strategy to regulate the evolution of valence- and free-electrons is a promising method to improve the production-transfer-utilization efficiency of photogenerated carriers.

Developing Zn-2Cu-xLi (x < 0.1 wt %) alloys with suitable mechanical properties, degradation behaviors and cytocompatibility for vascular stents.

Biodegradable Zn alloys show great potential for vascular stents due to their moderate degradation rates and acceptable biocompatibility. However, the poor mechanical properties limit their applications. In this study, low alloyed Zn-2Cu-xLi (x = 0.004, 0.01, 0.07 wt %) alloys with favorable mechanical properties were developed. The microstructure consists of fine equiaxed η-Zn grains, micron, submicron-sized and coherent nano ε-CuZn4 phases. The introduced Li exists as a solute in the η-Zn matrix and ε-CuZn4 phase, and results in the increase of ε-CuZn4 volume fraction, the refinement of grains and more uniform distribution of grain sizes. As Li content increases, the strength of alloys is dramatically improved by grain boundary strengthening, precipitate strengthening of ε-CuZn4 and solid solution strengthening of Li. Zn-2Cu-0.07Li alloy has the optimal mechanical properties with a tensile yield strength of 321.8 MPa, ultimate tensile strength of 362.3 MPa and fracture elongation of 28.0 %, exceeding the benchmark of stents. It also has favorable mechanical property stability, weak tension compression yield asymmetry and strain rate sensitivity. It exhibits uniform degradation and a little improved degradation rate of 89.5 µm∙year-1, due to the improved electrochemical activity by increased ε-CuZn4 volume fraction, and generates Li2CO3 and LiOH. It shows favorable cytocompatibility without adverse influence on endothelial cell viability by trace Li+. The fabricated microtubes show favorable mechanical properties, and stents exhibit an average radial strength of 118 kPa. The present study indicates that Zn-2Cu-0.07Li alloy is a potential and promising candidate for vascular stent applications. STATEMENT OF SIGNIFICANCE: Zn alloys are promising candidates for biodegradable vascular stents. However, improving their mechanical properties is challenging. Combining the advantages of Cu and trace Li, Zn-2Cu-xLi (x < 0.1 wt %) alloys were developed for stents. As Li increases, the strength of alloys is dramatically improved by refined grains, increased volume fraction of ε-CuZn4 and solid solution of Li. Zn-2Cu-0.07Li alloy exhibits a TYS exceeding 320 MPa, UTS exceeding 360 MPa and fracture EL of nearly 30 %. It shows favorable mechanical stability, degradation behaviors and cytocompatibility. The alloy was fabricated into microtubes and stents for mechanical property tests to verify application feasibility for the first time. This indicates that Zn-2Cu-0.07Li alloy has great potential for vascular stent applications.

A comparative study of confinement and layer modified Zr-based MOFs for the efficient removal of Cr(vi) from wastewater.

The GO- and SBA-15-modified UiO-66 adsorbents were developed for removal of trace Cr(vi) from wastewater and investigated to understand the effect of different hybrid ways on the absorption activity and reaction mechanism. The characterization results confirmed that the UiO-66 nanoparticles could be encapsulated by the SBA-15 matrix and anchored onto GO layers. Due to different exposure modes, the adsorption results showed that the GO-modified UiO-66 had better Cr(vi) trapping performance with the maximum removal efficiency of 97% within 3 min, presenting one of the most efficient Cr(vi) removal materials. Kinetic models showed that the adsorption process included fast, exothermic, spontaneous and pseudo-secondary chemical adsorption. By comparison with the Freundlich and Temkin model, the results revealed that the adsorption process of Cr(vi) by UiO-66@SBA-15 involved some multi-layer physical adsorption, while Cr(vi) was adsorbed onto the UiO-66@GO surface. The mechanism study also found that the fixation of Cr was the chemical action of UiO-66 on GO. Additionally, the encapsulated way increases the protection of UiO-55 from surface damage. In all, both hard-core-shell UiO-66@SBA-15 and piece UiO-66@Go increase the absorption activity of Cr(vi), but the different hybrid ways lead to different activities, absorption processes and regeneration abilities.

Catalytic conversion of cellulosic biomass to harvest high-valued organic acids.

Catalytic conversion of biomass provides an alternative way for the production of organic acids from renewable feedstocks. The emerging process contains complex reactions and strategies to cut down those complex biogenic materials into target molecules. Here, we review the catalytic conversion of cellulosic biomass toward high-valued organic acids. This work has summarized the key controlling reactions which lead toward formic acid, glycolic acid, or sugar acids in oxidative conditions and the main pathways for lactic acid or levulinic acid in the anaerobic environment from cellulosic biomass and its derivatives. We evaluate and compare different strategies and methods such as one-pot and two-step conversion. Additionally, the optimization of catalytic reactions has been discussed to realize the design of C-C coupling reactions, the development of multifunctional materials, and new efficient system. In all, this article gives an insight guide to precisely convert cellulosic biomass into target organic acids.

Reversible and irreversible stimuli-responsive chromism of a square-planar platinum(ii) salt.

A new simple Pt(ii) terpyridyl salt that shows reversible response towards acetonitrile and irreversible response towards methanol has been reported, accompanied with the colorimetric/luminescent changing from red to yellow. Experimentally and theoretically, the spectroscopic change derives from the hydrogen bonds between crystal water in the Pt(ii) terpyridyl salt and external organic molecules, and the different strength of hydrogen bond leads either reversible or irreversible stimuli-response. Furthermore, this Pt(ii) terpyridyl salt has been on one hand applied as a probe for sensing acetonitrile in water solution, with high selectivity, good reversibility, proper sensitivity and fast response rate, and on the other hand as advanced anticounterfeiting materials. The current study provides a new approach to acquire and design either reversible or irreversible stimuli-responsive luminescent materials.

Nanostructured Materials for Photothermal Carbon Dioxide Hydrogenation: Regulating Solar Utilization and Catalytic Performance.

Converting carbon dioxide (CO2) into value-added fuels or chemicals through photothermal catalytic CO2 hydrogenation is a promising approach to alleviate the energy shortage and global warming. Understanding the nanostructured material strategies in the photothermal catalytic CO2 hydrogenation process is vital for designing photothermal devices and catalysts and maximizing the photothermal CO2 hydrogenation performance. In this Perspective, we first describe several essential nanomaterial design concepts to enhance sunlight absorption and utilization in photothermal CO2 hydrogenation. Subsequently, we review the latest progress in photothermal CO2 hydrogenation into C1 (e.g., CO, CH4, and CH3OH) and multicarbon hydrocarbon (C2+) products. Finally, the relevant challenges and opportunities in this exciting research realm are discussed. This perspective provides a comprehensive understanding for the light-heat synergy over nanomaterials and instruction for rational photothermal catalyst design for CO2 utilization.

Generating high-valent iron-oxo ≡FeIV=O complexes by calcium sulfite activation in neutral microenvironments for enhanced degradation of CIP.

Although alkaline sulfite activation of ferrate (Fe(VI)) has advantages of fast response and high activity for degradation of organic contaminants, the specific production pathways of active species and the pH conditions still hinder its widespread application. Based on this, our study constructed a novel advanced oxidation process of calcium sulfite (CaSO3) could activated Fe(VI) continuously by Ca2+ buffering and investigated the mechanism under different pH values and CaSO3 dosages with ciprofloxacin as a target organic pollutant. The results showed that Ca2+ stabilized the process at a neutral/weakly alkaline microenvironment of pH 7-8, which could alleviate the hydrolysis of ≡FeIV=O by protons and iron hydroxyl groups. Besides, the removal of pollutants occurred efficiently when sulfate (SO32-) was excessive and had a 3:1 ratio of SO32- to Fe(VI), achieving more than 99% removal of electron-rich phenolic organic pollutants within 2 min. By adding different radical scavengers and combining electrochemical analysis methods and electron paramagnetic resonance spectroscopy techniques to revealed that the main active species in Fe(VI)/CaSO3 process were ≡FeIV=O/≡FeV=O. Furthermore, the reactivity of various sulfate species (such as SO32-, SO3•-, SO4•-, SO5•-) with Fe(VI) was calculated using density functional theory (DFT), and it was found that Fe(VI)-SO32- reaction has a much lower energy barrier (-36.08 kcal/mol), indicating that SO32- can readily activate Fe(VI) and generate ≡FeIV=O to attack the atoms with high Fukui index (f -) in organic pollutants. The above results confirm the feasibility of Fe(VI)/CaSO3 process. Thus, this study can theoretically and practically prove that the main active species is ≡FeIV=O, rather than SO4•- or •OH in Fe(VI)/CaSO3 process.

Alkali-oxygen cooking coupled with ultrasonic etching for directly defibrillation of bagasse parenchyma cells into cellulose nanofibrils.

A scheme combining alkali­oxygen cooking and ultrasonic etching cleaning was developed for the short range preparation of CNF from bagasse pith, which has a soft tissue structure and is rich in parenchyma cells. This scheme expands the utilization path of sugar waste sucrose pulp. The effect of NaOH, O2, macromolecular carbohydrates, and lignin on subsequent ultrasonic etching was analyzed, and it was found that the degree of alkali­oxygen cooking was positively correlated with the difficulty of subsequent ultrasonic etching. The mechanism of ultrasonic nano-crystallization was found to be the bidirectional etching mode from the edge and surface cracks of the cell fragments by ultrasonic microjet in the microtopography of CNF. The optimum preparation scheme was obtained under the condition of 28 % NaOH content and 0.5 MPa O2, which solves the problem of low-value utilization of bagasse pith and environmental pollution, providing a new possibility for the source of CNF.

Anchoring ultrasmall Pd nanoparticles by bipyridine functional covalent organic frameworks for semihydrogenation of acetylene.

Acetylene hydrogenation is a well-accepted solution to reduce by-products in the ethylene production process, while one of the key technical difficulties lies in developing a catalyst that can provide highly dispersed active sites. In this work, a highly crystalline layered covalent organic framework (COF) material (TbBpy) with excellent thermal stability was synthesized and firstly applied as support for ultrasmall Pd nanoparticles to catalyze acetylene hydrogenation. 100% of C2H2 conversion and 88.2% of C2H4 selectivity can be obtained at 120 °C with the space velocity of 70 000 h-1. The reaction mechanism was elucidated by applying a series of characterization techniques and theoretical calculation. The results indicate that the coordination between Pd and N atom in the bipyridine functional groups of COFs successfully increased the dispersibility and stability of Pd particles, and the introduction of COFs not only improved the adsorption of acetylene and H2 onto catalyst surface, but enhanced the electron transfer process, which can be responsible for the high selectivity and activity of catalyst. This work, for the first time, reported the excellent performance of Pd@TbBpy as a catalyst for acetylene hydrogenation and will facilitate the development and application of COFs materials in the area of petrochemicals.