A novel metal-free porous covalent organic polymer for efficient room-temperature photocatalytic CO_(2) reduction via dry-reforming of methane

At room temperature,the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane(DRM) is quite promising and challenging.Herein,we developed a novel covalent organic porous polymer (TPE-COP) with rapid charge separation of the electron–hole pairs for DRM driven by visible light at room temperature,which can efficiently generate syngas (CO and H_(2)).Both electron donor (tris(4-aminophenyl)amine,TAPA) and acceptor (4,4',4'',4'''-((1 E,1'E,1''E,1'''E)-(ethene-1,1,2,2-tetrayltetrakis (benzene-4,1-diyl))tetrakis (ethene-2,1-diyl))tetrakis (1-(4-formylbenzyl)quinolin-1-ium),TPE-CHO) were existed in TPE-COP,in which the push–pull effect between them promoted the separation of photogenerated electron–hole,thus greatly improving the photocatalytic activity.Density functional theory (DFT) simulation results show that TPE-COP can form charge-separating species under light irradiation,leading to electrons accumulation in TPE-CHO unit and holes in TAPA,and thus efficiently initiating DRM.After 20 h illumination,the photocatalytic results show that the yields reach 1123.6 and 30.8μmol g^(-1)for CO and H_(2),respectively,which are significantly higher than those of TPE-CHO small molecules.This excellent result is mainly due to the increase of specific surface area,the enhancement of light absorption capacity,and the improvement of photoelectron-generating efficiency after the formation of COP.Overall,this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field.

One-pot synthesis of mesosilica/nano covalent organic polymer composites and their synergistic effect in photocatalysis

Organic-inorganic hybrid materials provide a desirable platform for the development of novel functional materials.Here,we report the one-pot synthesis of mesoporous hybrid nanospheres by the in-situ sol-gel condensation of tetraethoxysilane around surfactant micelle-confined nano covalent organic polymer(nanoCOP)colloids.The hybrid nanospheres containing nanoCOPs uniformly distributed in the mesosilica network,inherited the visible light responsive properties of the nanoCOPs.The turnover frequency of the hybrid nanospheres is almost 12 times that of its corresponding bulk COP counterpart for the photocatalytic reductive dehalogenation of a-bromoacetophenone,which is attributed to activation of the Hantzsch ester reductant by the hydroxyl group.The existence of a volcano relationship between the activity and nano COP/mesosilica ratio confirmed the synergistic effect between nano COP and mesosilica.Our preliminary results suggest that hybridization of semiconductors and reactant-activating materials is an efficient strategy for enhancing the activity of a catalyst for photocatalysis.

Electron push-pull effects induced performance promotion in covalent organic polymer thin films-based memristor for neuromorphic application

Covalent organic polymer(COP)thin film-based memristors have generated intensive research interest,but the studies are still in their infancy.Herein,by controlling the content of hydroxyl groups in the aldehyde monomer,Py-COP thin films with different electronic push-pull effects were fabricated bearing distinct memory performances,where the films were prepared by the solid-liquid interface method on the ITO substrates and further fabricated as memory devices with ITO/Py-COPs/Ag architectures.The Py-COP-1-based memory device only exhibited binary memory behavior with an ON/OFF ratio of 1:10^(1.87).In contrast,the device based on Py-COP-2 demonstrated ternary memory behavior with an ON/OFF ratio of 1:10^(0.6):10^(3.1) and a ternary yield of 55%.The ternary memory mechanism of the ITO/Py-COP-2/Ag memory device is most likely due to the combination of the trapping of charge carriers and conductive filaments.Interestingly,the Py-COPs-based devices can successfully emulate the synaptic potentiation/depression behavior,clarifying the programmability of these devices in neuromorphic systems.These results suggest that the electronic properties of COPs can be precisely tuned at the molecular level,which provides a promising route for designing multi-level memory devices.

Long-lifespan aqueous alkaline and acidic batteries enabled by redox conjugated covalent organic polymer anodes

Herein,we introduce a redox conjugated covalent organic polymer(p-HATN,HATN=hexaazatrinaphthylene)anode bearing HATN species for long-lifespan aqueous alkaline and acidic batteries.The p-HATN features intriguing superhydrophilicity and unique wide pH adaptability,while the conjugated network and amorphous cross-linked structure further endow p-HATN with improved electron transport,facile ion diffusion and superior acid-alkali tolerability.As a result,p-HATN exhibits fast surface-controlled redox activity and superior stability for K^(+)and H^(+)ions storage with remarkable capacity retentions in three-electrode cells(88%capacity retention in 13 M KOH over 30000 cycles;nearly 100%capacity retention in 0.5 M H_(2)SO_(4)over 54000 cycles).Moreover,the assembled p-HATN//Ni(OH)_(2)cell with 13 M KOH and p-HATN//PbO_(2)cell with 0.5 M H_(2)SO_(4)also achieve ca-pacity retentions of 83%retention over 55000 cycles and 92%over 15000 cycles,respectively,outperforming most similar systems.This work sheds light on the rational design of advanced polymer anodes for long-lifespan alkaline and acidic batteries.

Electron donor–acceptor (D-A) tuning to achieve soluble covalent organic polymers for optoelectronic devices

Covalent organic polymers(COPs)have emerged as a unique class of luminescent polymers with pre-designed quasi-ordered architectures.However,their layered stacks and limited solubility preclude further processing for large-scale applications in devices,especially optoelectronic equipment.Herein,a universal strategy to adjust the electron donor–acceptor(D-A)moieties of the building blocks in COPs is proposed,achieved by in situ charge exfoliation of COP blocks into few-layer true solutions in(Lewis)acid and base media.The electron D-A moieties of the building blocks endow the COPs with the ability to accept or donate electrons,by altering the electron cloud distribution as well as the relative energy levels of the frontier molecular orbitals.The resultant soluble COPs can easily be processed into a uniform film by solution processing via the spin-coat method.The obtained COP-N achieves efficient and stable perovskite electroluminescence as a novel hole injection material on indium tin oxide,and the operating lifetime for a perovskite quantum dot light-emitting diodes device exceeds that of a poly(ethylene dioxythiophene):polystyrene sulphonate counterpart.This straightforward electronic regulation strategy provides a new avenue for the rational synthesis of processable reticular molecular polymers for practical electronic devices.

A Triformylphloroglucinol-based Covalent Organic Polymer:Synthesis,Characterization and Its Application in Visible-light-driven Oxidative Coupling Reactions of Primary Amines

A triformylphloroglucinol-based AiB2-typed covalent organic polymer(TFG-BPTH)was successfully constructed by the condensation reaction of triformylphloroglucinol(TFG)and 2.5-bis(2-propynyloxy)terephthalo-hydrazide(BPTH)under solvothermal conditions.The structure of the TFG-BPTH was confirmed by spectra tech-niques including FTIR and solid-state IC CP/MAS NMR spectroscopy.The mophological features of TFG-BPTH were analyzed using scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The TFG-BPTH possessed good thermal and chemical stability,and exhibited good photocatalytic activity as a metal-free heterogeneous catalyst for oxidation of amines to valuable imines under visible light irradiation using O2 as greer oxidant.In addition,the catalyst could be readily recovered from the reaction mixture by simple filtration and reused for at least five cycles without any observable change in structure and catalytic activity.

Microfluidic interface boosted synthesis of covalent organic polymer capsule

Microcapsules have been widely used in drug carriers,nano/microreactors,artificial organelles for their empty space and functional shell.Microcapsules synthesized from spherical liquid-liquid interface show ultrathin shell and large cavities.However,spherical liquid-liquid interfaces generated by stirring or sonicating are difficult in controlling the droplet size and preventing their coalescence,which results in inhomogeneous capsules.Here,we demonstrate a microfluidic interfacial synthetic method to produce microcapsules using the hot covalent organic polymers(COPs)coupled with Schiff-base reaction.A very high throughput of uniform and individual microdroplets about~1400 min^(-1)was generated under high flow rate for COP capsules fabrication.Acidic catalyst promoted amine and aldehyde condensation that reacted less than 1 s assured the polymerization occurred at the liquid-liquid interface regardless of the diffusion intensification in microfluidic system.COP capsules with shell thickness around 50 nm were flexible enough to response to slight interior capillary force and exterior filtration force to form origami structure and sealed flat membrane,respectively.Each of the interfacial synthesized capsule expressed large capacity by encapsulating 1.41×10^(-2)μg SiO_(2)nanoparticles as theoretically calculated.Thus,these properties make the COP capsules promising in,but not limited to,fast drug delivery and microreactors.

d-Orbital steered FeN_(4)moiety through N,S dual-site adjustation for zinc-air flow battery

The implementation of pristine covalent organic polymer(CO_(2)P)with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries(ZAFBs),but it still remains challenges in synergistically regulating their electronic states and structural porosity for the great device performance.Here,we conquer these issues by exploiting N and S co-doped graphene with COP rich in metal-ligand nitrogen to synergistically construct an effective catalyst for oxygen reduction reaction(ORR).Among them,the N and S co-doped sites with high electronegativity properties alter the number of electron occupations in the d orbital of the iron centre and form electron-transfer bridges,thereby boosting the selectivity of the ORR-catalysed four-electron pathway.Meanwhile,the introduction of COP materials aids the formation of pore interstices in the graphene lamellae,which both adequately expose the active sites and facilitate the transport of reactive substances.Benefiting from the synergistic effect,as-prepared catalyst exhibits excellent half-wave potentials(E_(1/2)=912 mV)and stability(merely 8.8%drop after a long-term durability test of 50000 s).Further,ZAFBs assembled with the N/SG@CO_(2)P catalyst demonstrate exceptional power density(163.8 mW cm^(-2))and continuous charge and discharge for approximately 140 h at 10 mA cm^(-2),outperforming the noble-metal benchmarks.