Organic Frameworks Research Articles

Advances in Membranes from Microporous Materials for Hydrogen Separation from Light Gases

With the pressing concern of the climate change, hydrogen will undoubtedly play an essential role in the future to accelerate the way out from fossil fuel‐based economy. In this case, the role of membrane‐based separation cannot be neglected since, compared with other conventional process, membrane‐based process is more effective and consumes less energy. Regarding this, metal‐based membranes, particularly palladium, are usually employed for hydrogen separation because of its high selectivity. However, with the advancement of various microporous materials, the status quo of the metal‐based membranes could be challenged since, compared with the metal‐based membranes, they could offer better hydrogen separation performance and could also be cheaper to be produced. In this article, the advancement of membranes fabricated from five main microporous materials, namely silica‐based membranes, zeolite membranes, carbon‐based membranes, metal organic frameworks/covalent organic frameworks (MOF/COF) membranes and microporous polymeric membranes, for hydrogen separation from light gases are extensively discussed. Their performances are then summarized to give further insights regarding the pathway that should be taken to direct the research direction in the future.

2D/2D Hydrogen‐Bonded Organic Frameworks/Covalent Organic Frameworks S‐scheme Heterojunctions for Photocatalytic Hydrogen Evolution

Hydrogen‐bonded organic frameworks (HOFs) demonstrate significant potential for application in photocatalysis. However, the low efficiency of electron‐hole separation and limited stability inhibit their practical utilization in photocatalytic hydrogen evolution from water splitting. Herein, the novel dual‐pyrene‐base supramolecular HOF/COF 2D/2D S‐scheme heterojunction between HOF‐H4TBAPy (Py‐HOF, H4TBAPy represents the 1,3,6,8‐tetrakis (p‐benzoic acid) pyrene) and Py‐COF was successfully established using a rapid self‐assembly solution dispersion method. Experimental and theoretical investigations confirm that the size‐matching of two crystalline porous materials enables the integrated heterostructure material with abundant surface reaction sites, strong interaction, and an enhanced S‐scheme built‐in electric field, thus significantly improving the efficiency of photogenerated charge carrier separation and stability. Notably, the optimal HOF/COF heterojunction achieves a photocatalytic hydrogen evolution rate of 390.68 mmol g−1 h−1, which is 2.28 times higher than that of pure Py‐HOF and 9.24 times higher than that of pure COF. These findings precisely acquire valuable atomic‐scale insights into the ingenious design of dual‐pyrene‐based S‐scheme heterojunction. This work presents an innovative perspective for forming supramolecular S‐scheme heterojunctions over HOF‐based semiconductors, offering a protocol for designing the powerful and strong‐coupling S‐scheme built‐in electric fields for efficient solar energy utilization.

Adsorption of malachite green dyes from aqueous solution by metal organic framework-5 incorporated coal fly ash (MOF-5/CFA)

Dye contamination of water is a global issue with significant environmental and health risks. This research explores the use of metal organic framework-5 (MOF-5) adsorbents modified with coal fly ash to effectively remove malachite green (MG) dye from water, addressing global dye pollution. Preliminary batch adsorption experiments showed that the addition of CFA to MOF-5 significantly increased the removal efficiency of MG dye (77.90 ± 1.74%) compared to using pristine MOF-5 (30.00 ± 2.14%). Batch adsorption studies showed that MG adsorption efficiency increased with shaking rate and contact time but decreased with adsorbent dosage. Temperature study reveals exothermic behavior of adsorption process. MOF-5/CFA adsorbents can be regenerated for up to four cycles. The results demonstrated that the highest adsorption efficiency of 80.32 ± 0.90% was achieved under the following conditions: a stirring speed of 300 rpm, a dosage of 0.3 g of MOF-5/CFA adsorbent, a temperature of 27 °C, 2 h contact time, and an initial dye concentration of 100 mg/L. Analysis of adsorption isotherms and kinetics revealed that the Langmuir isotherm and pseudo-second-order kinetic models provided the most accurate fit to the experimental data. FTIR analysis revealed significant functional groups in the prepared adsorbent and only minor spectral changes in the spent adsorbents. SEM analysis showed a rough, porous MOF-5/CFA surface before dye adsorption, becoming smoother and less porous afterwards. This study demonstrates the promise of MOF-5/CFA as an alternative adsorbent for the removal of MG dyes from water, paving the way for advances in wastewater treatment and the sustainable use of industrial waste materials.

Construction of two isomorphic multifunctional MOFs via a dual-ligand strategy for aromatic compounds detection and photocatalytic degradation performance

The development of multifunctional and structurally unique metal−organic frameworks (MOFs) presents a highly attractive yet challenging endeavor for chemists. In this study, we employ a dual-ligand strategy to synthesize two isomorphic Co/Zn MOFs, {[Co4(BMIP)3(MIP)4]·3DMF·H2O}n (SNUT-35-Co) and {[Zn4(BMIP)3(MIP)4]·2DMF·2H2O}n (SNUT-35-Zn). The photocatalytic performance of SNUT-35-Co and SNUT-35-Zn was evaluated using methylene blue (MB). Under UV/visible-light irradiation, the photocatalytic decolorization rates of MB for SNUT-35-Co and SNUT-35-Zn reached 95% within 140 min and 120 min, respectively, indicating their superior degradation. Notably, SNUT-35-Zn demonstrated exceptional detection capabilities for aromatic compounds, such as aniline and nitrobenzene, at lower concentration range without interference from other components. The detection limits for these two small molecules were found to be 0.430 and 0.431 μM, respectively. Additionally, both MOFs exhibited larger transient photocurrents and lower impedance in electrochemical measurements. The results suggested that the photocatalytic activities of MOF are influenced by their three-dimensional structures, which facilitate electrons passing due to the inherent semiconductor properties.

Zincophilic Sites Enriched Hydrogen‐Bonded Organic Framework as Multifunctional Regulating Interfacial Layers for Stable Zinc Metal Batteries

AbstractTo construct an efficient regulating layer for Zn anodes that can simultaneously address the issues of dendritic growth and side reactions is highly demanded for stable zinc metal batteries (ZMBs). Herein, we fabricate a hydrogen‐bonded organic framework (HOF) enriched with zincophilic sites as a multifunctional layer to regulate Zn anodes with controlled spatial ion flux and stable interfacial chemistry (MA‐BTA@Zn). The framework with abundant H‐bonds helps capture H2O and remove the solvated shells on [Zn(H2O)6]2+, leading to suppressed side reactions. The HOF layer also helps form electrolyte‐philic surfaces and expose Zn (002) crystal planes which benefit for rapid conduction and uniform deposition of Zn2+, and weakened sides reactions. Additionally, the electrochemically active zincophilic sites (C=O, −NH2 and triazine groups) favor the targeted guidance and penetration of Zn2+ and provide advantageous sites for uniform Zn deposition. High Young's modulus of the HOF layer further contributes to a high interfacial flexibility and stability against Zn plating‐associated stress. The MA‐BTA@Zn symmetric cells thereby obtain a substantially extended battery life over 1000 h at 4 mA cm−2. The MA‐BTA@Zn||Cu half‐cell demonstrates a highly reversible Zn stripping/plating process over 1500 cycles with impressive average Coulombic efficiency (CE) of 99.5 % at 10 mA cm−2.

Back Cover: Unlocking of Hidden Mesopores for Enzyme Encapsulation by Dynamic Linkers in Stable Metal−Organic Frameworks

Back Cover: Unlocking of Hidden Mesopores for Enzyme Encapsulation by Dynamic Linkers in Stable Metal−Organic Frameworks

Chiral Organic Salt Supported Pd Nanoparticles as Selective Heterogeneous Catalysts of Hydrogenation Reactions

AbstractIn this study, we report the synthesis of a new type of chiral crystalline organic porous salt CF2 derived from the ionic reaction between tetrakis(4‐sulfophenyl)methane (TSPM) and the tetra‐(S)‐prolylamide of tetrakis(4‐aminophenyl)methane, (S)‐TPPM, and its ability to stabilize 2 nm palladium nanoparticles to give a novel, nonpyrophoric, chiral, catalytic material Pd@CF2. The preparation of the catalyst was very simple and conducted in water. The heterogeneous catalytic performance of Pd@CF2 was tested in hydrogen reductions of olefins and substituted nitroaromatic compounds using Pd/C as a comparison to determine the specific features of the novel catalyst. Although both types of catalysts exhibited similar catalytic activity in case of reductions of diphenylacetylene and nitrobenzene, Pd@CF2 predominantly promoted the reduction of p‐nitrobenzaldehyde to p‐aminobenzyl alcohol whereas Pd/C gave p‐toluidine. The reduction of p‐dinitrobenzene led to predominant formation of p‐nitrophenylhydroxylamine if promoted by the novel catalyst and to a mixture of products if promoted by Pd/C. In addition, the introduction of p‐alkoxy groups onto nitrobenzenes slowed down the reduction with Pd@CF2 but had no influence on Pd/C activity. A hypothesis ascribing these observations to dissimilar equilibrium distributions of nitro and polar groups within the organic framework and the palladium metal surface is proposed to rationalize the selectivity of the novel catalytic material.

Hydrogen‐Bonded Organic Frameworks as a Carrier for Nanodrugs with Host–Guest Interaction for Smart Wound Dressing Applications

AbstractThis study introduces surface modification to conventional dressings utilizing adducts of a hydrogen‐bonded organic framework (HOF) with curcumin, curcumin–silver, curcumin‐zinc oxide nanoparticles, and citric acid drugs. Accordingly, eight HOF‐AMs and dressings modified with them were studied. The synthesized structures underwent characterization using various methods, including IR, 1H NMR, XRD, FE‐SEM, and EDX. FE‐SEM results show that the hexagonal morphology is maintained along with the crystal growth in the form of hexagonal tubes. In order to confirm the nanoscale nature of the structures, TEM analysis was conducted specifically for curcumin‐Ag nanoparticles and curcumin–ZnO nanoparticles which confirms the particle size smaller than 50 nm. Knowing the sensitivity of the release of the incorporated substances to temperature and pH, the controlled release of the drugs at two different temperatures (37 °C and 40 °C) and pH levels of 5.5, 7.4, and 9 at the modified dressings was investigated. Investigating the release of HOF‐AMs particles and modified dressings indicates that these products in both cases provide the possibility of drug release in alkaline and acidic pHs. Also, the results showed that increasing the temperature increases the release of curcumin particles in all its types. The modified dressings showed a loading capacity of more than 50 mg g−1.

Selective Monoborylation of Methane by a Mono Bipyridyl‐Nickel(II) Hydride Catalyst

We report the development of an earth‐abundant metal catalyst for methane C‒H borylation. The post‐synthetic metalation of bipyridine‐functionalized zirconium metal−organic framework (MOF) with NiBr2, followed by treatment of NaEt3BH affords MOF‐supported monomeric bipyridyl‐nickel(II) dihydride species via active site isolation. The heterogeneous and recyclable nickel catalyst selectively borylates methane at 200 ºC using pinacolborane (HBpin) to afford CH3Bpin in 61% yield with a turnover number (TON) up to 1388. The confinement of the active NiH2‐species within the uniformly porous MOF allows selective monoborylation of methane via shape‐selective catalysis by preventing the formation of sterically encumbered overborylated products. Unlike MOF‐Ni catalyst, its homogeneous control is almost inactive in methane borylation due to its intermolecular decomposition. Our mechanistic investigation, including spectroscopic, kinetic, and control experiments, as well as DFT calculations, revealed that stabilizing mononuclear bipyridyl‐nickel dihydride and diboryl species by MOF is crucial for achieving efficient methane borylation via turnover‐limiting σ‐bond metathesis. This work shows promise in designing MOF‐based abundant metal catalysts for the chemoselective functionalization of methane and other inert molecules into valuable chemicals.

A 3D Robust and Microporous B←N Framework with 8‐connected Sandwich Nodes for Efficient Separation of Hexane Isomers

Recently B←N organic frameworks (BNFs) have gained substantial attention owing to their unique dative bond energy, which imparts them with specialized functionalities across a broad spectrum of applications. Despite previous reports on BNFs with permanent porosity, research endeavors towards three‐dimensional (3D) BNFs with similar properties are scarce, with no report of robust 3D BNFs featuring permanent porosity to date. Herein, electrostatic complementarystrategy is proposed to construct the first example of 3D robust and microporous BNF, BNF‐100, featuring a reo topology with 8‐connected sandwich nodes assembled via dative B←N bonds. The activated form BNF‐100a exhibits excellent chemical stability and permanent porosity with Langmuir surface area of 645.9 m2 g−1 and pore volume of 0.23 cm3 g−1. BNF‐100a can efficiently separate hexane isomers through sieving mechanisms, as confirmed by vapor adsorption experiments and dynamic breakthrough tests, surpassing the performance of most MOF materials. Finally, we achieved the purification of different branched hexane isomers using a single breakthrough column in a combined breakthrough and purging experiment, which is the first reported instance in the literature on hexane isomer separation.

A 3D Robust and Microporous B←N Framework with 8-connected Sandwich Nodes for Efficient Separation of Hexane Isomers.

Recently B←N organic frameworks (BNFs) have gained substantial attention owing to their unique dative bond energy, which imparts them with specialized functionalities across a broad spectrum of applications. Despite previous reports on BNFs with permanent porosity, research endeavors towards three-dimensional (3D) BNFs with similar properties are scarce, with no report of robust 3D BNFs featuring permanent porosity to date.Herein,electrostatic complementarystrategyisproposedto constructthe first example of3Drobust and microporousBNF,BNF-100, featuring areotopology with 8-connected sandwich nodes assembled via dative B←N bonds. The activated formBNF-100aexhibits excellent chemical stability and permanent porosity with Langmuir surface area of 645.9 m2g-1and pore volume of 0.23 cm3 g-1.BNF-100acan efficiently separate hexane isomers through sieving mechanisms, as confirmed by vapor adsorption experiments and dynamic breakthrough tests, surpassing the performance of most MOF materials.Finally, we achieved the purification of different branched hexane isomers using a single breakthrough column in a combined breakthrough and purging experiment, which is the first reported instance in the literature on hexane isomer separation.

Simultaneous achieving color‐tuning long persistent luminescence and phosphorescent quantum yield of 81.05% in 2D organic metal halide perovskite

AbstractIonically bonded organic metal halide perovskite‐like luminescent materials, which incorporate organic cations and metal halides, have emerged as a versatile multicomponent material system. However, these materials still face challenges in terms of low phosphorescence quantum yields and limited long persistent luminescence (LPL) colors. Herein, we present the design and synthesis of an intraligand charge‐transfer organic‐based metal halide perovskite‐like material, in which organic cations form a compact supramolecular hydrogen‐bonded organic framework (HOF) structure, exhibiting crystallization‐induced phosphorescence emission of ligand, while metal halides form a unique two‐dimensional (2D) structure that displays intrinsic self‐trapped excitons (STE) emission under the radiation of UV light. Notably, the metal halide hybrid is found to exhibit enhanced phosphorescent photoluminescence efficiency of up to 81.05% and tunable LPL from cyan to orange compared to the pristine organic phosphor, due to the structural distortion and scaffolding effects of 2D metal halides as well as a well‐packed HOF structure. Optical characterizations and theoretical calculations reveal that charge transfer from organic cations and halogen to ligand as well as STE from inorganic layers are responsible for the tunable LPL. Meanwhile, the high‐efficiency phosphorescent quantum yield is attributed to stronger hydrogen bond stacking as well as structural distortion of metal halogen bands. Thus, the obtained LPL provides potentials in anti‐counterfeiting, security systems, and so on.

Two Co(II) Isostructural Bifunctional MOFs via Mixed-Ligand Strategy: Syntheses, Crystal Structure, Photocatalytic Degradation of Dyes, and Electrocatalytic Water Oxidation.

The solvothermal reactions involving cobalt ions with 5-methylisophthalic acid (H2MIP) and 1,3-bis(2-methylimidazol)propane (BMIP) yielded two cobalt(II) organic frameworks: {[Co4(MIP)4(BMIP)3]·1/2DMA}n (SNUT-31) and {[Co4(MIP)4(BMIP)3]·(EtOH)2·H2O]}n (SNUT-32) where DMA represents N,N-dimethylacetamide and EtOH signifies ethyl alcohol. Single-crystal X-ray diffraction analyses reveal that SNUT-31 and SNUT-32 possess an isomorphic structure, featuring a unique 2-fold interpenetration of 3D frameworks in a parallel manner. Notably, both SNUT-31 and SNUT-32 demonstrate remarkable performance in electrocatalytic oxygen evolution reactions and exhibit exceptional photocatalytic degradation capabilities against a model comprising three distinct dyes: rhodamine B, methyl orange, and methyl blue.

Integrated Monomer Synthesis and Framework Assembly: Achieving Isoreticular Modulation of Hydrogen‐Bonded Organic Frameworks

Systematic construction of isoreticular hydrogen‐bonded organic frameworks (HOFs) promises tailored material properties crucial for diverse applications, yet is challenging due to the weak, flexible, and non‐directional nature of hydrogen bonds. Herein, we develop an “integrated monomer synthesis‐framework assembly” (ISA) methodology for constructing a series of isoreticular HOFs. Unlike traditional methods where monomers are first synthesized and then assembled into HOFs, the ISA system employs dicyandiamide rigid hydrogen‐bonded hexameric clusters as connecting nodes to covalently react with planarized C3‐symmetric cyano‐precursors (C3‐CPs) to generate diaminotriazine (DAT) monomers, while simultaneously inducing the directional assembly into isoreticular (6,3)‐net hcb topological DAT‐C6‐HOFs. The pore sizes and microenvironments of the resulting DAT‐C6‐HOFs can be precisely tuned by varying the structural modulation (length and steric hindrance) of the π‐bridge on C3‐CPs, enabling highly selective sensing towards perfluorooctanoic acid over other homologous molecules, that are difficult to be separated and detected by chromatography. Overall, the ISA methodology facilitates the scalable creation of families of isostructural HOFs and provides a customized structural platform for investigating factors beyond topology that impact the capturing, releasing, and responding to guest molecules.

Synergistic C2H2 Binding Sites in Hydrogen‐Bonded Supramolecular Framework for One‐Step C2H4 Purification from Ternary C2 Mixture

AbstractPurification of C2H4 from the ternary C2 hydrocarbon mixture in one step is of critical significance but still extremely challenging according to its intermediate physical properties between C2H6 and C2H2. Hydrogen‐bonded organic frameworks (HOFs) stabilized by supramolecular interactions are emerging as a new kind of adsorbents that facilitate green separation. However, it remains a problem to efficiently realize the one‐step C2H4 purification from C2H6/C2H4/C2H2 mixture because of the low C2H2/C2H4 selectivity. We herein report a robust microporous HOF (termed as HOF‐TDCPB) with dense O atoms and aromatic rings distributed on the pore surface which provide C2H6 and C2H2 preferred environment simultaneously. Dynamic breakthrough experiments indicate that HOF‐TDCPB can not only obtain high‐purity C2H4 from binary C2 mixture, but also firstly realize one‐step C2H4 purification from ternary C2H6/C2H4/C2H2 mixture, with the C2H4 productivity of 3.2 L/kg (>99.999 %) for one breakthrough cycle. Furthermore, HOF‐TDCPB displays outstanding stability in air, organic solvents and water, which endow it excellent cycle performance even under high‐humidity conditions. Theoretical calculations indicate that multiple O sites on pore channels can create synergistic binding sites for C2H2, thus affording overall stronger multipoint interactions.

Anchoring Frustrated Lewis Pair Active Sites on Copper Nanoclusters for Regioselective Hydrogenation.

In recent years, the concept of Frustrated Lewis Pairs (FLPs), which consist of a combination of Lewis acid (LA) and Lewis base (LB) active sites arranged in a suitable geometric configuration, has been widely utilized in homogeneous catalytic reactions. This concept has also been extended to solid supports such as zeolites, metal oxide surfaces, and metal/covalent organic frameworks, resulting in a diverse range of heterogeneous FLP catalysts that have demonstrated notable efficiency and recyclability in activating small molecules. This study presents the successful immobilization of FLP active sites onto the surface of ligand-stabilized copper nanoclusters with atomic precision, leading to the development of copper nanocluster FLP catalysts characterized by high reactivity, stability, and selectivity. Specifically, thiol ligands containing 2-methoxyl groups were strategically designed to stabilize the surface of [Cu34S7(RS)18(PPh3)4]2+ (where RSH = 2-methoxybenzenethiol), facilitating the formation of FLPs between the surface copper atoms (LA) and ligand oxygen atoms (LB). Experimental and theoretical investigations have demonstrated that these FLPs on the cluster surface can efficiently activate H2 through a heterolytic pathway, resulting in superior catalytic performance in the hydrogenation of alkenes under mild conditions. Notably, the intricate yet precise surface coordination structures of the cluster, reminiscent of enzyme catalysts, enable the hydrogenation process to proceed with nearly 100% selectivity. This research offers valuable insights into the design of FLP catalysts with enhanced activity and selectivity by leveraging surface/interface coordination chemistry of ligand-stabilized atomically precise metal nanoclusters.

In situ Construction of Single‐Atom Electronic Bridge on COF to Enhance Photocatalytic H2 Production

AbstractPhotocatalytic hydrogen production is one of the most valuable technologies in the future energy system. Here, we designed a metal‐covalent organic frameworks (MCOFs) with both small‐sized metal clusters and nitrogen‐rich ligands, named COF‐Cu3TG. Based on our design, small‐sized metal clusters were selected to increase the density of active sites and shorten the distance of electron transport to active sites. While another building block containing nitrogen‐rich organic ligands acted as a node that could in situ anchor metal atoms during photocatalysis and form interlayer single‐atom electron bridges (SAEB) to accelerate electron transport. Together, they promoted photocatalytic performance. This represented the further utilization of Ru atoms and was an additional application of the photosensitizer. N2‐Ru‐N2 electron bridge (Ru‐SAEB) was created in situ between the layers, resulting in a considerable enhancement in the hydrogen production rate of the photocatalyst to 10.47 mmol g−1 h−1. Through theoretical calculation and EXAFS, the existence position and action mechanism of Ru‐SAEB were reasonably inferred, further confirming the rationality of the Ru‐SAEB configuration. A sufficiently proximity between the small‐sized Cu3 cluster and the Ru‐SAEB was found to expedite electron transfer. This work demonstrated the synergistic impact of small molecular clusters with Ru‐SAEB for efficient photocatalytic hydrogen production.

Long‐Range π–π Stacking Brings High Electron Delocalization for Enhanced Photocatalytic Activity in Hydrogen‐Bonded Organic Framework

AbstractUnlike many studies that regulate transport and separation behaviour of photogenerated charge carriers through controlling the chemical composite, our work demonstrates this goal can be achieved through simply tuning the molecular π–π packing from short‐range to long‐range within hydrogen‐bonded organic frameworks (HOFs) without altering the building blocks or network topology. Further investigations reveal that the long‐range π–π stacking significantly promotes electron delocalization and enhances electron density, thereby effectively suppressing electron‐hole recombination and augmenting the charge transfer rate. Simultaneously, acting as a porous substrate, it boosts electron density of Pd nanoparticle loaded on its surfaces, resulting in remarkable CO2 photoreduction catalytic activity (CO generation rate: 48.1 μmol/g/h) without the need for hole scavengers. Our study provide insight into regulating the charge carrier behaviours in molecular assemblies based on hydrogen bonds, offering a new clue for efficient photocatalyst design.

Defect Engineering in a Nanoporous Thulium-Organic Framework in Catalyzing Knoevenagel Condensation and Chemical CO2 Fixation.

Defect engineering is an extremely effective strategy for modifying metal-organic frameworks (MOFs), which can break through the application limitations of traditional MOFs and enhance their functionality. Herein, we report a highly robust nanoporous thulium(III)-organic framework, {[Tm2(BDCP)(H2O)5](NO3)·3DMF·2H2O}n (NUC-105), with [Tm(COO)2(H2O)]n chains and [Tm2(COO)4(H2O)8] dinuclears as metal nodes and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (BDCP) linkers. In NUC-105, each of the four chains of [Tm(COO)2]n and the two rows of [Tm2(COO)4(H2O)8] units is unified by the organic skeleton, resulting in a rectangular nanochannel with dimensions of 15.35 Å × 11.29 Å, which leads to a void volume of 50%. It is worth mentioning that the [Tm2(COO)4(H2O)8] cluster is very rare in terms of its higher level of associated water molecules, implying that the activated host framework can serve as a strong Lewis acid. NUC-105a exhibited great heterogeneous catalytic performance for CO2 cycloaddition with epoxides under the reaction conditions (0.60 mol % NUC-105a, 5.0 mol % n-Bu4NBr, 65 °C, 5 h), ensuring exclusive selectivity and high conversion rates. In addition, NUC-105a's strong catalytic impact on the Knoevenagel condensation of aldehydes and malononitrile can be attributed to the collaboration between the drastically unsaturated Lewis acidic Tm3+ centers and Lewis basic pyridine groups.

Understanding the role played by Cu nanoparticles embedded in situ in a carbonaceous matrix as sulfur host for lithium-sulfur batteries

The lithium-sulfur (Li-S) battery is a promising alternative to Li-ion batteries as an energy storage system, owing to its higher capacity and specific energy values. To tackle its intrinsic problems, the element copper (Cu) is an attractive option given both its excellent conductivity and its ability to interact with highly reactive polysulfides. Here, we propose the use of a carbon/copper composite (90.5:9.5 wt ratio) obtained by thermal decomposition of a single precursor based on a Cu(II) oleate/oleic acid complex and eliminating the use of H2 as a reducing agent as commonly reported. Cu nanoparticles (mean particle size around 15 nm in diameter) which are highly dispersed on an amorphous carbon matrix derived from an organic framework, enhance both the conductivity and the ability for the chemical adsorption of lithium polysulfides (LiPSs), and thus increasing the reaction efficiency. Poor cycling stability, less specific capacity, and diminished rate capability were observed when the Cu content was reduced to around 70 % through treatment with concentrated nitric acid. This confirms the electrocatalytic role of the metal.