Dialdehyde Monomers Research Articles

Efficient adsorption of pesticides by porous organic polymers based on imine/aminal linkages

Porous organic polymers (POPs) are promising materials for pesticide adsorption from wastewater due to their high surface area and tunable porous structure. MPT-TPA-POPs were synthesized in green solvents using inexpensive diamines and dialdehyde monomers to form imine and aminal linkages. This study investigated for the first time the adsorption and removal effects of pesticides Forchlorfenuron (CPPU) and Acetamiprid (ACE) using MPA-TPA-POPs adsorbent. FTIR, SEM, EDS, BET, and XPS analyses were utilized to examine changes in functional groups, morphology, elemental composition, specific surface area, and pore volume of MPT-TPA-POPs before and after CPPU and ACE adsorption. At an initial concentration of 50 mg/L, with a dosage of 0.5 g/L, a pH of 7, a temperature of 298 K, and an adsorption time of 120 min, the maximum removal rates for CPPU and ACE are achieved at 99.94 % and 68.44 %, respectively. The quasi-second-order kinetic and Langmuir isotherm model were deemed more appropriate for accurately describing this adsorption process. Thermodynamically, the adsorption process was observed to be spontaneous and exothermic. Simultaneously, during cyclic adsorption-desorption experiments, the adsorption capacity of MPT-TPA-POPs material showed no significant decline even after six cycles. The findings of this research suggest that MPT-TPA-POPs can act as a green, eco-friendly, cost-efficient, and effective adsorbent for eliminating CPPU and ACE pesticides from water, offering an economically feasible approach to pesticide removal.

Monomethylated Tröger's-base-containing polyimidazolinium salt as an efficient catalyst for cycloaddition of CO2 to epoxides

In this work, the model reaction of benzaldehyde and ammonium chloride has been studied by detailed product analysis and characterization. Subsequently, amarine and iso-amarine hydrochlorides (1, 2), dimethylated amarine and iso-amarine ionic salts (3, 4), together with monomethylated Tröger's-base ionic salt (6) have been separately synthesized and characterized. In addition, their catalytic performance towards the cycloaddition of CO2 to epichlorohydrin is compared under identical conditions. It is observed that their catalytic activity follows the order of 3 ≈ 4 >6 > 1 ≈ 2. Inspired by the highly catalytic activity of 3, 4 and 6, a novel monomethylated Tröger's-base-containing polyimidazolinium salt (namely PMDD-IL) has been synthesized by one-pot reaction of Tröger's-base-containing dialdehyde monomer (MDD) with ammonium chloride followed by treatment with excess iodomethane in the presence of sodium hydride. The as-synthesized PMDD-IL network exhibits highly catalytic activity towards the cycloaddition of CO2 to epoxides, providing nearly quantitative selectivity (99%) and conversion (99%) over a wide substrate scope of epoxides at atmospheric CO2 pressure (epichlorohydrin, 100 °C/10 h; epibromohydrin, 100 °C/12 h; glycidyl phenyl ether, 100 °C/24 h; styrene oxide, 100 °C/24 h; and 2-butyloxirane, 100 °C/24 h). The excellent catalytic activity of PMDD-IL network can be ascribed to the high nucleophilicity of iodine anion along with the strong interactions between PMDD-IL network and CO2 molecules.

Pore Size Adjustment Strategy for the Fabrication of Molecularly Imprinted Covalent Organic Framework Nanospheres at Room Temperature for Selective Extraction of Zearalenone in Cereal Samples.

Covalent organic frameworks (COFs) are attractive adsorbents for sample pretreatment due to their unique structure and properties. However, the selectivity of COFs for the extraction of hazardous compounds is still limited due to the lack of specific interactions between COFs and targets. Herein, we report a pore size adjustment strategy for room-temperature synthesis of molecularly imprinted COF (MICOF) for selective extraction of zearalenone (ZEN) in complex food samples. The three-dimensional building block tetra(4-aminophenyl) methane was used as a functional monomer, while dialdehyde monomers with different numbers of benzene ring were used to adjust the pore size of MICOF to match with the size of ZEN molecules. The prepared MICOF gave the largest adsorption capacity of 177.2 mg g-1 and the highest imprinting factor of 10.1 for ZEN so far. MICOF was used as the adsorbent for dispersed solid-phase extraction in combination with high-performance liquid chromatography for the determination of trace ZEN in cereals. The high selectivity of the developed method allows simple aqueous standard calibration for the matrix effect-free determination of ZEN in food samples. The limit of detection and the recoveries of the developed method were 0.21 μg kg-1 and 93.7-101.4%, respectively. The precision for the determination of ZEN was less than 3.8% (RSD, n = 6). The developed method is promising for the selective determination of ZEN in complex matrices.

Near-Infrared Absorbing Para-Azaquinodimethane Conjugated Polymers Synthesized via the Transition-Metal-Free Route toward Efficient Photothermal Conversion.

Conjugated polymers with strong absorption in the second near-infrared (NIR-II) window have multiple applications. However, the development of new type of NIR-II conjugated polymers via facile and green methods remains challenging. Herein, this work reports a mild and convenient transition-metal-free method to synthesize near-infrared absorbing quinoidal conjugated polymers containing para-azaquinodimethane (AQM) moieties. The AQM quinoidal conjugated polymers with unique molecular structures and tunable optoelectronic properties can be synthesized by combining the Knoevenagel polycondensation of aromatic dialdehyde monomers with commercially available 1,4-diacetyl-2,5-piperazinedione and the following alkylation reaction. The resultant polymer PQ-DPP shows remarkable NIR-II absorption with a narrow band gap of about 1.08eV. PQ-DPP nanoparticles exhibit high photothermal conversion efficiency of up to 48% under 1064nm laser irradiation (1W cm-2) endowing this polymer with potential in bio-related applications.

Photo-induced synthesis of polymeric nanoparticles and chemiluminescent degradable materials via flow chemistry.

We report the photo-induced, additive-free, continuous synthesis of polymeric particles using flow chemistry. Not only can these particles be formed under ambient conditions in a solely light-induced precipitation polymerisation, they can be prepared via continuous flow techniques to up-scale the synthetic process. We carefully assess the flow chemical parameters and analyse the resulting particles quantitatively using scanning electron microscopy (SEM). Particle formation is a direct result of the step-growth polymerisation via a photochemically induced AA + BB Diels-Alder reaction, which we herein base on the dialdehyde monomer (AA) derived from the sustainable precursor, thymol. By employing a peroxyoxalate bismaleimide (BB), we introduce particles that can be selectively degraded on-demand, self-reported by light emission through chemiluminescence.

Synthesis of a covalent organic framework with hetero-environmental pores and its medicine co-delivery application

The topology type and the functionalization of pores play an important role in regulating the performance of covalent organic frameworks. Herein, we designed and synthesized the covalent organic framework with hetero-environmental pores using predesigned asymmetrical dialdehyde monomer. According to the results of structural characterization, crystallinity investigation, and theoretical calculation, the hetero-environmental pores of the obtained framework are regarded as the alternant arrangement. The distinctive hetero pore structure leads the designed material to show more advantages as compared with control materials in loading both hydrophobic and hydrophilic antibiotics for wound healing. This dual-antibiotic strategy can expand the antibacterial range as compared with the single antibiotic one, and reduce the generation of drug resistance. In summary, this strategy for designing covalent organic frameworks with hetero-environmental pores can extend the structural variety and provide a pathway for improving the practical application performance of these materials.

Narrow-Pore Engineering of Vinylene-Linked Covalent Organic Frameworks with Weak Interaction-Triggered Multiple Responses.

Vinylene-linked covalent organic frameworks (COFs) are emerging as promising crystalline materials, but their narrow pore engineering is severely impeded by the weak reversibility of the carbon-carbon double bond formation reaction, which has led to less exploration of their ultramicroporous structures and properties. Herein, we developed a single aromatic ring-based tetratopic monomer, tetramethylpyrazine, which undergoes a smooth Knoevenegal condensation at its four arylmethly carbon atoms with linear aromatic dialdehyde monomers upon the self-catalyzed activation of pyridine nitrogen-containing monomers in the presence of an organic anhydride. This has resulted in the formation of two vinylene-linked COFs, which both crystallized in orthorhombic lattices, and layered in AA stacking fashions along the vertical directions. They exhibit high surface areas and well-tailored ultramicropore sizes up to 0.5 nm. The unique cross-linking mode at two pairs of para-positions of each pyrazine unit through carbon-carbon double bonds afford them with π-extended conjugation over the in-plane backbones and substantial semiconducting characters. The resultant COFs can be well-dispersed in water to form stable sub-microparticles with negative charges (zeta potentials: ca. -30 mV), and exhibiting tunable aggregation behaviors through protonation/deprotonation. As a consequence, they exhibit pore-size-dependent colorimetric responses to various anions with different pKa values in high selectivity.

Narrow‐Pore Engineering of Vinylene‐Linked Covalent Organic Frameworks with Weak Interaction‐Triggered Multiple Responses

AbstractVinylene‐linked covalent organic frameworks (COFs) are emerging as promising crystalline materials, but their narrow pore engineering is severely impeded by the weak reversibility of the carbon‐carbon double bond formation reaction, which has led to less exploration of their ultramicroporous structures and properties. Herein, we developed a single aromatic ring‐based tetratopic monomer, tetramethylpyrazine, which undergoes a smooth Knoevenegal condensation at its four arylmethly carbon atoms with linear aromatic dialdehyde monomers upon the self‐catalyzed activation of pyridine nitrogen‐containing monomers in the presence of an organic anhydride. This has resulted in the formation of two vinylene‐linked COFs, which both crystallized in orthorhombic lattices, and layered in AA stacking fashions along the vertical directions. They exhibit high surface areas and well‐tailored ultramicropore sizes up to 0.5 nm. The unique cross‐linking mode at two pairs of para‐positions of each pyrazine unit through carbon‐carbon double bonds afford them with π‐extended conjugation over the in‐plane backbones and substantial semiconducting characters. The resultant COFs can be well‐dispersed in water to form stable sub‐microparticles with negative charges (zeta potentials: ca. −30 mV), and exhibiting tunable aggregation behaviors through protonation/deprotonation. As a consequence, they exhibit pore‐size‐dependent colorimetric responses to various anions with different pKa values in high selectivity.

Investigations on thermomechanical and structure properties of pure and wet polyimine networks by molecular dynamics simulations

Polyimine polymer is a kind of covalent adaptable networks with excellent reprocessing and self-healing properties. It has attracted wide attentions in recent years because it can release stress by reversible bond exchange reactions without using catalysts. Since polyimines containing -NH- groups are strongly hydrophilic, the influence of water content on their thermomechanical and structure properties is significant. In this study, we establish atomic models involving diamine and dialdehyde monomers combined with triamine cross-linkers to investigate the thermomechanical and structure properties of polyimine networks. Furthermore, different amounts of water molecules are added into networks to explore the interaction between polyimines and water molecules in aqueous polyimine systems. It is concluded that the increase of cross-linking density and conversion degree will improve the thermomechanical properties of polyimines. The water molecules in the aqueous polyimine systems will reduce glass transition temperature and enhance plasticity. Moreover, the diffusion coefficient is found to positively correlate with water content and temperature. Further researches on the structure of polyimines shows that the radius of gyration of polyimines and the radial distribution function of water molecules around the polyimines are also sensitive to temperature and water content. This investigation provides comprehensive information on different factors affecting the thermomechanical properties of pure and wet polyimine networks and contributes toward predicting the evolution of properties of polyimines under different circumstances.

Green, General and Low‐cost Synthesis of Porous Organic Polymers in Sub‐kilogram Scale for Catalysis and CO2 Capture

AbstractPorous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large‐scale production. Herein, we report the synthesis of imine and aminal‐linked POPs using inexpensive diamine and dialdehyde monomers in green solvents. Theoretical calculations and control experiments show that using meta‐diamines is crucial for forming aminal linkages and branching porous networks from [2+2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub‐kilogram quantities at a relatively low cost. Proof‐of‐concept studies demonstrate that the POPs can be used as high‐performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost‐effective approach for large‐scale synthesis of various POPs.

Green, General and Low-cost Synthesis of Porous Organic Polymers in Sub-kilogram Scale for Catalysis and CO2 Capture.

Porous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large-scale production. Herein, we report the synthesis of imine and aminal-linked POPs using inexpensive diamine and dialdehyde monomers in green solvents. Theoretical calculations and control experiments show that using meta-diamines is crucial for forming aminal linkages and branching porous networks from [2+2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub-kilogram quantities at a relatively low cost. Proof-of-concept studies demonstrate that the POPs can be used as high-performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost-effective approach for large-scale synthesis of various POPs.

Unexpected Direct Synthesis of Tunable Redox-Active Benzil-Linked Polymers via the Benzoin Reaction.

Strategies for the sustainable synthesis of redox-active organic polymers could lead to next-generation organic electrode materials for electrochemical energy storage, electrocatalysis, and electro-swing chemical separations. Among redox-active moieties, benzils or aromatic 1,2-diones are particularly attractive due to their high theoretical gravimetric capacities and fast charge/discharge rates. Herein, we demonstrate that the cyanide-catalyzed polymerization of simple dialdehyde monomers unexpectedly leads to insoluble redox-active benzil-linked polymers instead of the expected benzoin polymers, as supported by solid-state nuclear magnetic resonance spectroscopy and electrochemical characterization. Mechanistic studies suggest that cyanide-mediated benzoin oxidation occurs by hydride transfer to the solvent, and that the insolubility of the benzil-linked polymers protects them from subsequent cyanolysis. The thiophene-based polymer poly(BTDA) is an intriguing organic electrode material that demonstrates two reversible one-electron reductions with monovalent cations such as Li+ and Na+ but one two-electron reduction with divalent Mg2+. As such, the tandem benzoin-oxidation polymerization reported herein represents a sustainable method for the synthesis of highly tunable and redox-active organic materials.

Closed-Loop Recycling of Poly(Imine-Carbonate) Derived from Plastic Waste and Bio-based Resources.

Closed-loop recycling of polymers represents the key technology to convert plastic waste in a sustainable fashion. Efficient chemical recycling and upcycling strategies are thus highly sought-after to establish a circular plastic economy. Here, we present the selective chemical depolymerization of polycarbonate by employing a vanillin derivative as bio-based feedstock. The resulting di-vanillin carbonate monomer was used in combination with various amines to construct a library of reprocessable poly(imine-carbonate)s, which show tailor-made thermal and mechanical properties. These novel poly(imine-carbonate)s exhibit excellent recyclability under acidic and energy-efficient conditions. This allows the recovery of monomers in high yields and purity for immediate reuse, even when mixed with various commodity plastics. This work provides exciting new insights in the design of bio-based circular polymers produced by upcycling of plastic waste with minimal environmental impact.

Diverse Proton-Conducting Nanotubes via a Tandem Macrocyclization and Assembly Strategy

Macrocycles that assemble into nanotubes exhibit emergent properties stemming from their low dimensionality, structural regularity, and distinct interior environments. We report a versatile strategy to synthesize diverse nanotube structures in a single, efficient reaction by using a conserved building block bearing a pyridine ring. Imine condensation of a 2,4,6-triphenylpyridine-based diamine with various aromatic dialdehydes yields chemically distinct pentagonal [5 + 5], hexagonal [3 + 3], and diamond-shaped [2 + 2] macrocycles depending on the substitution pattern of the aromatic dialdehyde monomer. Atomic force microscopy and in solvo X-ray diffraction demonstrate that protonation of the macrocycles under the mild conditions used for their synthesis drives assembly into high-aspect ratio nanotubes. Each of the pyridine-containing nanotube assemblies exhibited measurable proton conductivity by electrochemical impedance spectroscopy, with values as high as 10-3 S m-1 (90% R.H., 25 °C) that we attribute to differences in their internal pore sizes. This synthetic strategy represents a general method to access robust nanotube assemblies from a universal pyridine-containing monomer, which will enable systematic investigations of their emergent properties.

Bio-inspired construction of ion conductive pathway in covalent organic framework membranes for efficient lithium extraction

Summary As the most sophisticated separation system, biological membranes have served as natural prototypes for the design of artificial membranes because they provide high permeability and solute selectivity, owing to the presence of specialized ion channels. However, developing stable and selective artificial ion channels remains a formidable challenge. Herein, we demonstrate the construction of lithium nanochannels in two-dimensional covalent organic frameworks (COFs) to create biomimetic membranes. Implanted lithiophilic oligoethers conferred specificity and facilitated Li+ diffusion along the pore pathway of the COF. The ion channel characteristics were indicated by reversal potential measurements, showing that the relative permeability decreased in the order Li+ > K+ > Na+ > Ca2+ > Mg2+. The Li+ transfer was enhanced, while other ions were obstructed, allowing for high selectivity and permeability. A Li+/Mg2+ separation factor of 64 was achieved, confirming high lithium affinity. This study may serve as a design principle to develop selective artificial membranes for effective ion separation.

A biomass-based Schiff base vitrimer with both excellent performance and multiple degradability

Vitrimers with both excellent performance and multiple degradability were obtained by curing vanillin dialdehyde monomer with triamino T403.

Dual-mode coupling copolymerization of aryl dialdehyde and alkynylaldehyde monomers via Concurrent McMurry olefination and alkyne [2+2+2] cycloaddition trimerization reactions mediated by a low-valent titanium reagent

The application of a low-valent titanium reagent recently developed in our group, Ti(O-i-Pr)4/Me3SiCl/Mg, to the McMurry coupling polymerization of aryl dialdehyde monomers and [2 + 2 + 2] cycloaddition polymerization of aromatic diyne monomers is described. Furthermore, on the basis of these reactions, a low-valent titanium-mediated dual-mode coupling copolymerization of aryl dialdehyde and alkynylaldehyde monomers via concurrent McMurry olefination and alkyne cyclotrimerization reactions is proposed.

Exploring Oxidative NHC-Catalysis as Organocatalytic Polymerization Strategy towards Polyamide Oligomers.

The polycondensation of diamines and dialdehydes promoted by an N-heterocyclic carbene (NHC) catalyst in the presence of a quinone oxidant and hexafluoro-2-propanol (HFIP) is herein presented for the synthesis of oligomeric polyamides (PAs), which are obtained with a number-average molecular weight (Mn ) in the range of 1.7-3.6 kg mol-1 as determined by NMR analysis. In particular, the utilization of furanic dialdehyde monomers (2,5-diformylfuran, DFF; 5,5'-[oxybis(methylene)]bis[2-furaldehyde], OBFA) to access known and previously unreported biobased PAs is illustrated. The synthesis of higher molecular weight PAs (poly(decamethylene terephthalamide, PA10T, Mn = 62.8 kg mol-1 ; poly(decamethylene 2,5-furandicarboxylamide, PA10F, Mn = 6.5 kg mol-1 ) by a two-step polycondensation approach is also described. The thermal properties (TGA and DSC analyses) of the synthesized PAs are reported.

Orientation control of polyazomethine thin films by polarized UV-assisted vapor deposition polymerization

Vapor deposition polymerization (VDP) was developed as a solvent-free preparation technique to form insoluble polymer film on a substrate by direct deposition of monomers. As π-conjugated polymer semiconductors, aromatic polyazomethine thin films are prepared through the co-evaporation of a dialdehyde monomer and a diamine monomer by VDP. In addition, it is reported that substances with an azomethine bond (N=CH) can be isomerized by UV irradiation. In this study, we investigate the molecular orientation in polyazomethine thin films based on the photoisomerization of the azomethine bond induced by polarized UV light irradiation during VDP.

Vanillin-Based Polyschiff Vitrimers: Reprocessability and Chemical Recyclability

In this study, dynamic imine covalent bonds were introduced into vanillin-based vitrimers networks, endowing thermosets with hot-reprocessing ability and chemical recyclability under acid hydrolysis. First, dialdehyde monomer, which was synthesized from lignin-derived vanillin monomer, was reacted with conventional amine cross-linkers to form dynamic imine bond networks. Even after three hot-processing cycles, the tensile strength and elongation at break of polyschiff vitrimers could be recovered at least up to 71.2 and 72.8%, respectively, through the imine metathesis reaction. Importantly, the dialdehyde monomers showed enhanced recyclability under strong acid solution and could be reused to regenerate polyschiff vitrimers. These characteristics of reprocessablility, recyclablility, and biobased monomer present a feasible way to satisfy the demands of sustainability.