Functional Side Groups Research Articles

Regulating the Photoisomerization of Covalent Organic Framework for Enhanced Photocatalytic Hydrogen Evolution†

Comprehensive SummaryCovalent organic framework (COF) is a desirable platform to tailor electronic properties for improving photocatalytic performances. However, the study on excited‐state configurations that determine photogenerated carrier dynamics has long been neglected. Herein, we concentrate on the molecular design of β‐ketoenamine‐linked COFs to drive their photoisomerization via the excited‐state intra‐molecular proton transfer (ESIPT), which can induce the partial keto‐to‐enol tautomerization and accordingly rearrange the photoinduced charge distribution. We demonstrate that the push‐pull electronic effect of functional side groups attached on the framework linkers is directly correlated with the ESIPT process. The phenylene linkers modified with electron‐withdrawing cyano‐groups reinforce the ESIPT‐induced tautomerization, leading to the in situ partial enolization for extended π‐conjugation and rearranged electron‐hole distribution. In contrast, the electron‐rich linkers limit the photoisomerization of COF and suppress the photoinduced electron accumulation. Thus, the maximum hydrogen evolution rate is achieved by the cyano‐modified COF, reaching as high as 162.72 mmol·g–1·h–1 with an apparent quantum efficiency of 13.44% at 475 nm, which is almost 11.5‐fold higher than those of analogous COFs with electron‐rich linkers. Our work opens up an avenue to control over the excited‐state structure transformation for enhanced photochemical applications.

Hierarchically Porous Polyacetylene Networks: Adsorptive Photocatalysts for Efficient Bisphenol A Removal from Water.

In this article, we report a series of functionalized polyacetylene-type networks formed by chain-growth insertion coordination polymerization in high internal phase emulsions (HIPEs). All polymerized HIPEs (polyHIPEs) contain a hierarchically structured, 3D-interconnected porous framework consisting of a micro-, meso- and macropore system, resulting in exceptionally high specific surface areas (up to 1055 m2·g-1) and total porosities of over 95%. The combination of π-conjugated and hierarchically porous structure in one material enabled the use of these polyacetylene polyHIPEs as adsorptive photocatalysts for the removal of chemical contaminants from water. All polyacetylene polyHIPEs demonstrated high efficiency in the adsorption of bisphenol A from water (up to 48%) and the subsequent photocatalytic degradation. Surprisingly, high adsorption capacity did not affect the photocatalytic efficiency (up to 58%). On the contrary, this dual function seems to be very promising, as some polyacetylene polyHIPEs almost completely removed bisphenol A from water (97%) through the adsorption-photooxidation mechanism. It also appears that the presence of polar functional side groups in the polyacetylene backbone improves the contact of the polyacetylene network with the aqueous bisphenol A solution, which can thus be more easily adsorbed and subsequently oxidized, compensating for the lower specific surface area of some networks, namely, 471 and 308 m2·g-1 in the case of 3-ethynylphenol- and 3-ethynylaniline-based polyacetylene polyHIPEs, respectively.

Construction of Polycarbonates with Pendant Multifunctional Groups via a One-Step CO2/ Diepoxide Copolymerization Approach.

A "one-step" strategy has been demonstrated for the tunable synthesis of multifunctional aliphatic polycarbonates (APCs) with ethylene oxide (EO), ethylene carbonate (EC), and cyclohexene oxide (CHO) side groups by the copolymerization of 4-vinyl-1-cyclohexene diepoxide with carbon dioxide under an aminotriphenolate iron/PPNBz (PPN = bis(triphenylphosphine)-iminium, Bz = benzoate) binary catalyst. By adjusting the PPNBz-to-iron complex ratio and incorporating auxiliary solvents, the content of functional side groups can be tuned within the ranges of 53-75% for EO, 18-47% for EC, and <1-7% for CHO. The yield and molecular weight distribution of the resulting multifunctional APCs are affected by the viscosity of the polymerization system. The use of tetrahydrofuran as an auxiliary solvent enables the preparation of narrow-distribution polycarbonates at high conversion. This work presents a novel perspective for the preparation of tailorable multifunctional APCs.

Exploring Functional Polymers in the Synthesis of Luminescent ZnO Quantum Dots for the Detection of Cr6+, Fe2+, and Cu2.

The main aim of this work is to demonstrate that well-defined methacrylate-based copolymers with oligoethylene glycol side chains and functional groups such as thiol and glycidyl, obtained by photo-initiated reversible addition-fragmentation chain transfer (RAFT) in ethanol, are highly suitable as templates in the synthesis and protection of ZnO quantum dots (ZnO QDs) with remarkable photoluminescent properties. While the affinity of thiol groups to metallic surfaces is well established, their interaction with metal oxides has received less scrutiny. Furthermore, under basic conditions, glycidyl groups could react with hydroxyl groups on the surface of ZnO, representing another strategy for hybrid synthesis. The size and crystalline morphology of the resulting hybrids were assessed using DLS, TEM, and XRD, indicating that both polymers, even with a low proportion of functional groups (5% mol) are appropriate as templates and ligands for ZnO QDs synthesis. Notably, thiol-containing polymers yield hybrids with ZnO featuring excellent quantum yield (up to 52%), while polymers with glycidyl groups require combination with the organosilane aminopropyl triethoxysilane (APTES) to achieve optimal results. In both cases, these hybrids exhibited robust stability in both ethanol and aqueous environments. Beyond fundamental research, due to the remarkable photoluminescent properties and affordability, these hybrid ZnO QDs are expected to have potential applications in biotechnology and green science; in particular, in this study, we examined their use in the detection of environmental contaminants like Fe2+, Cr6+, and Cu2+. Specifically, the limit of detection achieved at 1.13 µM for the highly toxic Cr6+ underscores the significant sensing capabilities of the hybrids.

Synthesis of chitosan-based flocculant by dielectric barrier discharge modification and its flocculation performance in wastewater treatment.

As a typical type of organic flocculant, chitosan is limited by its poor water solubility and narrow pH range application. Grafting modification can improve chitosan's solubility and availability through linking macromolecular chains with other types of water-soluble groups or functional side groups. In this study, dielectric barrier discharge (DBD) was used to active the surface of chitosan, then activated chitosan was polymerized with acrylamide to synthesize a chitosan-based flocculant, chitosan-acrylamide (CS-AM). During the synthesis of CS-AM, the optimal conditions were determined as follows: discharge time of 5 min, discharge power of 60 W, total monomer mass concentration of 80 g L-1, polymerization time of 3 h, polymerization temperature of 70 °C, and m(CS) : m(AM) ratio of 1 : 3. The structure and morphological characteristics of CS-AM were investigated and analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and N2 physical adsorption, respectively. The removal efficiency of kaolin suspension and CNTs suspension can reach up to 95.9% and 90.2% after flocculation of CS-AM. Furthermore, the zeta potential of the supernatant from the CS-AM treated kaolin suspension at different pH values was examined, and the flocculation mechanism of CS-AM was analyzed. This study provides new ideas for the preparation and development of modified chitosan and broadens its application in water treatment.

Artificial intelligence driven molecule adsorption prediction (AIMAP) applied to chirality recognition of amino acid adsorption on metals.

Predicting the adsorption structure of molecules has long been a challenging topic given the coupled complexity of surface binding sites and molecule flexibility. Here, we develop AIMAP, an Artificial Intelligence Driven Molecule Adsorption Prediction tool, to achieve the general-purpose end-to-end prediction of molecule adsorption structures. AIMAP features efficient exploration of the global potential energy surface of the adsorption system based on global neural network (G-NN) potential, by rapidly screening qualified adsorption patterns and fine searching using stochastic surface walking (SSW) global optimization. We demonstrate the AIMAP efficiency in constructing the Cu-HCNO6 adsorption database, encompassing 1 182 351 distinct adsorption configurations of 9592 molecules on three copper surfaces. AIMAP is then utilized to identify the best adsorption structure for 18 amino acids (AAs) on achiral Cu surfaces and the chiral Cu(3,1,17) S surface. We find that AAs chemisorb on copper surfaces in their highest deprotonated state, through both the carboxylate-amino skeleton and side groups. The chiral recognition is identified for the d-preference of Asp, Glu, and Tyr, and l-preference for His. The physical origin for the enantiospecific adsorption is thus rationalized, pointing to the critical role of the competitive adsorption between functional side groups and the carboxylate-amino skeleton at surface low-coordination sites.

Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance.

Mechanically robust anion-exchange membranes (AEMs) with high conductivity and long-term alkali resistance are needed for water electrolysis application. In this work, aryl-ether free polyaromatics containing isatin moieties were prepared via super acid-catalyzed copolymerization, followed by functionalization with alkaline stable cyclic quaternary ammonium (QA) cationic groups, to afford high performance AEMs for application in water electrolysis. The incorporation of side functional cationic groups (pyrrolidinium and piperidinium) onto a polymer backbone via a flexible alkyl spacer aimed at conductivity and alkaline stability improvement. The effect of cation structure on the properties of prepared AEMs was thoroughly studied. Pyrrolidinium- and piperidinium-based AEMs showed similar electrolyte uptakes and no obvious phase separation, as revealed by SAXS and further supported by AFM and TEM data. In addition, these AEMs displayed high conductivity values (81. 5 and 120 mS cm-1 for pyrrolidinium- and piperidinium-based AEM, respectively, at 80 °C) and excellent alkaline stability after 1 month aging in 2M KOH at 80 °C. Especially, a pyrrolidinium-based AEM membrane preserved 87% of its initial conductivity value, while at the same time retaining its flexibility and mechanical robustness after storage in alkaline media (2M KOH) for 1 month at 80 °C. Based on 1H NMR data, the conductivity loss observed after the aging test is mainly related to the piperidinium degradation that took place, probably via ring-opening Hofmann elimination, alkyl spacer scission and nucleophilic substitution reactions as well. The synthesized AEMs were also tested in an alkaline water electrolysis cell. Piperidinium-based AEM showed superior performance compared to its pyrrolidinium analogue, owing to its higher conductivity as revealed by EIS data, further confirming the ex situ conductivity measurements.

Synthesis of Functional Isosorbide-Based Polyesters and Polyamides by Passerini Three-Component Polymerization.

A new family of functional isosorbide-based polyesters and polyamides with high glass transition temperature are prepared via Passerini-three component polymerization (P-3CP). To optimize the P-3CP conditions, the influence of the polymerization solvent, temperature, feed ratio on the molar mass of final polymers are investigated. The higher molar mass (up to 10100 g/mol) and yield (>70%) are achieved under mild conditions (30 °C, standard atmosphere). Functional side groups, such as alkenyl, alkynyl and methyl ester, were introduced into polymer structure via P-3CP by using functional isocyanides. The obtained polyesters and polyamides are characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). All polymers are thermal stable and amorphous with variable glass transition temperatures (Tg). The obtained polyester has Tg up to 87.5 °C, while the Tg of polyamides (ISPA-2) is detected to be 97.5 °C depending on the amide bonds in the polymer backbone and the benzene ring side groups. The cytotoxicity is investigated by the CCK-8 assay against mBMSC cells to confirm the biological safety. Overall, this novel strategy provides an efficient approach to produce functional isosorbide-based polyesters and polyamides, which are promising prospect for being applied to biodegradable materials.

Photoluminescence mechanism and optoelectronic responses of Janus pyrene and Janus coronene QDs for OLEDs & nanomedical applications

We carry out a first-principles study on manipulating the optoelectronic and photoluminescence properties of hexagonal and diamond-shaped graphene quantum dots, adopting asymmetric surface functionalization using hydrogen atoms on one side and molecular functional groups (-OH, -COOH, -CHO and -NH2) on the opposite side, leading to Janus quantum dots (JQDs). The results revealed considerable energetic and chemical stability characterizing the studied JQDs. In addition, the gap energy strongly depends on the variation of the shape and functionalization of the surface, giving rise to unexpected behaviour. Interestingly, the inclusion of quasiparticle corrections enhances the electronic character of all configurations, producing results in good agreement with experimental measurements. Optical absorption and excitonic binding energy are significantly altered by the basal plane decoration. At last, energy splitting of the excited states and TDDFT results have confirmed that our structures exhibit tunable photoluminescence from the near ultraviolet to the infrared region of the solar spectrum, making them promising for a new generation of applications.

Atomic Oxygen-Induced Surface Erosion Behavior and Mechanical Degradation of Polyether Ether Ketone via Reactive Molecular Dynamics Simulations.

Atomic oxygen (AO) collision is one of the most serious threats to polymeric materials exposed to the space environment, yet understanding the structural changes and degradation of materials caused by AO impact remains a tremendous issue. Herein, we systematically evaluate the erosion collision and mechanical degradation of polyether ether ketone (PEEK) resin under hypervelocity AO impact using reactive molecular dynamics simulations. The interaction process and local evolution mechanism between high-speed AO and PEEK are investigated for the first time, suggesting that AO will either be scattered or adsorbed by PEEK, which is strongly correlated with the main degraded species evolution including O2, OH, CO, and CO2. Different AO fluxes and AO incidence angle simulations indicate that high-energy AO collision on the surface transfers kinetic energy to PEEK's thermal energy, thus inducing mass loss and surface penetration mechanisms. Vertically impacted AO causes less erosion on the PEEK matrix, rather than obliquely. Furthermore, PEEK chains modified with functional side groups are comprehensively investigated by 200 AO impact and high strain rate (1010 s-1) tensile simulations, demonstrating that the spatial configuration and stable benzene functionality of phenyl side groups can significantly improve the AO resistance and mechanical properties of PEEK at 300 and 800 K. This work revealed useful insights into the interaction mechanisms between AO and PEEK at the atomic scale and may provide a protocol for screening and designing new polymers of high AO tolerance.

Effect of the Functional Groups of Polymers on Their Adsorption Behavior on Graphene Oxide Nanosheets

AbstractGraphene‐based polymer nanocomposites are emerging materials for both fundamental research and industrial applications. The influence of polymer functional groups on their adsorption behavior onto graphene oxide (GO) nanosheets is investigated, with poly(methyl methacrylate) (PMMA), poly(methyl methacrylate‐co‐methacrylic acid) (PMMA‐co‐MAA), and poly(methacrylic acid) (PMAA) having the same backbone but different functional side groups selected as the model polymers. Fourier transform infrared spectroscopy and X‐ray diffraction results confirm the interfacial interaction between the polymer and GO. Thermogravimetric analysis reveals notable enhancements in the amount of the adsorbed polymer up to 30.6 wt.% for PMMA‐co‐MAA/GO and 49.7 wt.% PMAA/GO compared with 18.7 wt.% for PMMA/GO. The water contact angle decreases from 71.3o for PMMA/GO to 69.1° for PMMA‐co‐MAA/GO and to 61.2° for PMAA/GO. The further washing process reduces the adsorption amount for the polymer/GO hybrid. Overall, the polar functional groups of the polymer directly influence the polymer adsorption behavior onto GO.

Synthesis and characterization of water-borne vanillin derived copolymers containing dynamic imine cross-links

In the effort toward the production of circular plastics, the use of lignin-derived aromatic building blocks such as vanillin is interesting due to their functionality. Nonetheless, the water-borne emulsion polymerization of acrylic monomers derived from vanillin is still lacking. Vanillin can be readily functionalized with a methacrylate group for the radical polymerization to yield polymers containing functional aldehyde side groups. The functionality can be exploited via imine formation to produce vitrimers, a class of cross-linked recyclable polymers. Besides recycling, synthesis via a water-borne emulsion polymerization is desired to reduce the negative contribution of solvents on the environment and health. In the present work, polymethacrylates based on 2-(methacryloyloxy)ethyl vanillin and 2-octyl acrylate were synthesized via a emulsion polymerization approach to produce a water-borne latex. A latex with a small particle size (49 nm) and solid content of 31 wt% was obtained. For comparative purposes, a similar polymer was synthesized via solution polymerization. Both polymers were cross-linked using a multifunctional amine to produce recyclable imine vitrimers. This research investigates the unique combination of water-borne synthesis and vitrimer polymers, and therefore contributes to future development of vitrimer latex products such as coatings and films.

Effect of crosslinker to monomer ratio on the adhesion and size distribution of silver nanoparticles grown on poly (methacrylic acid) microspheres

In this study poly methacrylic acid (MAA) microparticles were synthesized with variations in methylene-bis-acrylamide (MBA), with MBA in the role of the crosslinker. The as produced microparticles serve as substrates for the growth of silver nanoparticles while evaluating the effect of different crosslinker content. Each formulation was assessed in terms of silver nanoparticle adhesion, size distribution and silver quantity. Experimental evidence reveals that while incorporating crosslinker above 20 wt% with respect to the monomer, silver nanoparticle adhesion to the polymer surface increases, whereas in formulations above 35 wt% microparticle morphology hinders silver ion binding and the subsequent formation of silver nanoparticles. In addition, TEM microcopy combined with image classification analysis reported that in the range of 20–35 wt% MBA content, silver nanoparticle size distribution can be tuned. Evidently, MBA content between 20 wt% and 35 wt% (in relation to MAA) exhibits a dynamic state where carboxylic acid terminated functional side groups and amino-terminal side groups provide a synergistic effect in silver ion binding thus opening a functional pathway towards the controlled synthesis of silver nanoparticles.

Synthesis of novel lignin model compounds labeled with alkynyl and their potential application

Vanillin was applied to yield 2-O-propargyl coniferin, onto which alkynyl groups could be introduced at ortho position of the benzene ring, thus avoiding changes in the structure of the lignin side chains and functional groups on the benzene ring.

Triazine and Thiophene-Containing Conjugated Polymer Network Emitter-Based Solution-Processable Stable Blue Organic LEDs

The development of solution-processable fluorescent materials with blue electroluminescence has recently attracted considerable research interest for organic light-emitting diode (OLED) applications. Whereas, conjugated polymer frameworks (CPFs) or networks (CPNs) have attained tremendous research interest due to their vast potential in a variety of cutting-edge applications including photocatalysis, sensing, gas storage, energy storage, and so on. These framework/network materials without side chains or functional groups on their backbone are generally insoluble in common organic solvents and less solution-processable for electronic device applications. Herein, we have reported two triazine-based highly fluorescent and wide-band gap donor–acceptor conjugated polymer networks (CPNs) by coupling a 3-substituted thiophene (donor) unit with a triazine ring (acceptor) through a phenyl ring spacer. Two different side chains, alkyl and oligoethylene glycol, are rationally introduced into the 3-position of thiophene in the polymer network to make them solution-processable. Further physicochemical and optoelectronic characterizations of these emitters are performed in detail, and the effects of the side chain functionality and polarity on the above-mentioned properties are also thoroughly investigated. OLEDs based on these CPNs as emitters show a maximum external quantum efficiency of 2.3% with a maximum brightness of 2541 cd/m2 and a maximum current efficiency of 2.8 cd/A with blue emission [Commission Internationale de l’éclairage (CIE) coordinates of (0.17, 0.19)]. To the best of our knowledge, this may be the first example of conjugated polymer network material emitters being successfully designed, fabricated, and tested for solution-processable blue OLEDs. These results also demonstrate the high potential of the conjugated polymer network emitters for future blue or other color OLED applications.

Functional molecular cross‐linked zeolite nanosheets heighten ion selectivity and conductivity of flow battery membrane

AbstractMembranes with high ion selectivity and conductivity are critical for the wide application of electrochemical energy conversion and storage devices. Herein, functional molecular cross‐linked two‐dimensional zeolite nanosheets (ZN) with ‐NH2 and ‐SO3H groups are prepared and incorporated into sulfonated poly (ether ether ketone) (SPEEK) polymer matrix. These embedded nanosheets act as strong barrier to vanadium ions, while their internal pores provide transport channels for protons. In addition, the side functional groups grafted on ZN not only effectively enhance the surface affinity, but also bind and arrange the sulfonic acid groups of the polymer matrix to construct a continuous fast proton transfer pathway along the interface between SPEEK and ZN. Consequently, the hybrid membranes exhibit synchronously enhanced conductive‐ion selectivity and impressive performance with coulombic efficiency (CE) of ~99.0% and energy efficiency (EE) of ~85.0% at 120 mA cm−2, which is much higher than these of pure SPEEK (CE: ~97.8%, EE: ~78.4%) and Nafion 212 membranes (CE: ~96.3%, EE: ~80.1%). This functional‐designed hybrid approach provides a general strategy to develop high‐performance proton conductive membranes for energy‐related applications.

Graphene Functionalized with Imidazole Derivatives as Nanotransducers for Electrochemically Detecting Isothiazolinone Biocides

Isothiazolinones, which are widely used as chemical additives in many industries, may lead to skin irritation and allergies, thereby adversely influencing human health and the environment. Therefore, this paper proposes an efficient strategy for screening nanohybrid transducers to selectively detect 2-octyl-3-isothiazolinone (OIT) as a representative isothiazolinone. Chemical receptor (CR) candidates consisting of two parts: a reactive imidazole unit and side functional group for covalent conjugation with graphene and noncovalent interaction with the target, respectively, were designed. Five CR structures were selected and synthesized based on density-functional-theory calculations. The synthesized CRs were anchored to graphene for electrochemical transduction. The alkyl groups calculated to have the highest chemical affinities toward OIT were introduced in the CR/graphene nanohybrids (CGNHs). The electrochemical responses of the CGNHs toward OIT depended on the CR type, OIT concentration, and applied potential. Therefore, the combination of five CGNHs as a transducer with different potentials enabled the facile and effective detection of OIT (1–200 mg L–1) from the interferences through principal component analyses. The best CR corresponded to the dodecyloxy group, and the optimal measurement conditions included a scan rate of 25 mV s–1 and applied potentials of −0.75, 0.08, and 1.30 V (vs Ag/AgNO3). The proposed strategy can facilitate the efficient development of nanotransducers for identifying different types of chemical species such as biocides.

Effect mechanism of nitrogen injection into fire-sealed-zone on residual-coal re-ignition under stress in goaf

Coal is the one of foundations of energy and economic structure in China, while the unsealing of coal mine fires would cause a great risk of coal re-ignition. In order to explore the influence of pressure-bearing state on the re-ignition characteristics for residual coal, the uniaxial compression equipped with a temperature-programmed device was built. The scanning electron microscope, synchronous thermal analyzer and Fourier transform infrared absorption spectrometer was applied to investigate the microscopic structure and thermal effect of the coal samples. Moreover, the microscopic effect of uniaxial stress on coal re-ignition is revealed, and the re-ignition mechanism is also obtained. As the uniaxial stress increasing, the number, depth and length of the fractures of the pre-treated coal increases. The application of uniaxial stress causes the thermal conductivity to change periodically, enhances the inhibition of injecting nitrogen on heat transfer and prolonges the duration of oxidation exothermic. The content of oxygen-containing functional groups has a high correlation with apparent activation energy, and coal samples at 6 MPa is more probability to re-ignite while the fire zone is unsealed. Uniaxial stress could control the re-ignition mechanism by changing the structure of fractures and pores. The side chains and functional groups of coal structure are easier to be broken by thermal-stress coupling. The higher the ·OH content, the more difficult coal samples would be re-ignited. The research results would lay a solid theoretical foundation for the safe unsealing of closed fire-areas underground, tighten the common bond between the actual industry and the experimental theory in closed fire-areas underground, and provide the theoretical guidance for coal re-ignition preventing.

Effects of furanic compounds from biomass pyrolysis on ketonization reaction: The role of oxygenated side groups

Ketonization of biomass-derived oxygenates is promising for sustainable production of platform chemicals, but the catalyst activity will be severely inhibited by furanic compounds. To investigate the mechanism of the inhibition effect, furanic compounds with different side functional groups were chosen for co-ketonization with propanoic acid over CeO2. Results from 12 h continuous reaction showed that conversion of propanoic acid changed slightly when furan was co-fed with propanoic acid, while decreased significantly from 100 % for sole propanoic acid feeding to <55 % when co-feeding with furfural and furfuralcohol. Therefore, the inhibition ability followed the order of furfural ≈ furfuralcohol ≫ furan, which agreed well with the coke yield on the spent catalysts (51 %, 47 %, and 22 %, respectively). DFT calculation indicated that furfural and furfuralcohol, with the adsorption energy of 17–19 kJ·mol−1, were much easier to adsorb on the catalyst than furan (11 kJ·mol−1). However, the lack of α-H of these furanic compounds led to their conversion into aromatic coke components. It is evidenced that the oxygenated side groups, rather than the furan ring, are responsible for the inhibition effect. Successive ketonization-combustion-ketonization tests revealed that simple air calcination can hardly recover the activity of the spent CeO2. This investigation gives new insights into the inhibitory impact of furans on the ketonization activity.

Two-Dimensional Imide-Based Covalent Organic Frameworks with Tailored Pore Functionality as Separators for High-Performance Li-S Batteries.

Modifying the separator of lithium-sulfur batteries (LSBs) is considered to be one of the most effective strategies for relieving the notorious polysulfide shuttle effect. Constructing a stable, lightweight, and effective LSB separator is still a big challenge but highly desirable. Herein, a stable and lightweight imide-based covalent organic framework (COF-TpPa) is facilely fabricated on reduced graphene oxide (rGO) through an oxygen-free solvothermal technique. With the directing effect of rGO and changing the side functional group of the monomer, the morphology and the pore tailoring of COF-TpPa can be simultaneously achieved and two-dimensional (2D) COF nanosheets with different functionalities (such as -SO3H and -Cl) are successfully constructed on rGO films. The specific functional groups inside the COF's pore channels and the narrowed pore size result in efficient absorption and restriction of Li2Sn for weakening the "shuttle effect". Meanwhile, the 2D COF nanosheets on the rGO is a favorable morphology for better exploiting pores inside the COF materials. As a result, the COF-SO3H-modified separator, consisting of rGO and COF-TpPa-SO3H, exhibits a high specific capacity (1163.4 mA h/g at 0.2 C) and a desirable cyclic performance (60.2% retention rate after 1000 cycles at 2.0 C) for LSBs. Our study provides a feasible strategy to rationally design functional COFs and boosts their applications in various energy storage systems.