Hypercrosslinked porous polymer materials: design, synthesis, and applications

Porous organic polymers (POPs) for environmental remediation

Modern global industrialization along with the ever-increasing growth of the population has resulted in continuous enhancement in the discharge and accumulation of various toxic and hazardous chemicals in the environment. These harmful pollutants, including toxic gases, inorganic heavy metal ions, anthropogenic waste, persistent organic pollutants, toxic dyes, pharmaceuticals, volatile organic compounds, etc., are destroying the ecological balance of the environment. Therefore, systematic monitoring and effective remediation of these toxic pollutants either by adsorptive removal or by catalytic degradation are of great significance. From this viewpoint, porous organic polymers (POPs), being two- or three-dimensional polymeric materials, constructed from small organic molecules connected with rigid covalent bonds have come forth as a promising platform toward various leading applications, especially for efficient environmental remediation. Their unique chemical and structural features including high stability, tunable pore functionalization, and large surface area have boosted the transformation of POPs into various macro-physical forms such as thick and thin-film membranes, which led to a new direction in advanced level pollutant removal, separation and catalytic degradation. In this review, our focus is to highlight the recent progress and achievements in the strategic design, synthesis, architectural-engineering and applications of POPs and their composite materials toward environmental remediation. Several strategies to improve the adsorption efficiency and catalytic degradation performance along with the in-depth interaction mechanism of POP-based materials have been systematically summarized. In addition, evolution of POPs from regular powder form application to rapid and more efficient size and chemo-selective, "real-time" applicable membrane-based application has been further highlighted. Finally, we put forward our perspective on the challenges and opportunities of these materials toward real-world implementation and future prospects in next generation remediation technology.

Hyper-Crosslinked Porous Organic Nanomaterials: Structure-Oriented Design and Catalytic Applications

Hyper-crosslinked porous organic nanomaterials, especially the hyper-crosslinked polymers (HCPs), are a unique class of materials that combine the benefits of high surface area, porous structure, and good chemical and thermal stability all rolled into one. A wide range of synthetic methods offer an enormous variety of HCPs with different pore structures and morphologies, which has allowed HCPs to be developed for gas adsorption and separations, chemical adsorption and encapsulation, and heterogeneous catalysis. Here, we present a systematic review of recent approaches to pore size modulation and morphological tailoring of HCPs and their applications to catalysis. We mainly compare the effects of pore size modulation and morphological tailoring on catalytic applications, aiming to pave the way for researchers to develop HCPs with an optimal performance for modern applications.

Earth Abundant Oxidation Catalysts for Removal of Contaminants of Emerging Concern from Wastewater: Homogeneous Catalytic Screening of Monomeric Complexes

Twenty novel Mn, Fe, and Cu complexes of ethylene cross-bridged tetraazamacrocycles with potentially copolymerizable allyl and benzyl pendant arms were synthesized and characterized. Multiple X-ray crystal structures demonstrate the cis-folded pseudo-octahedral geometry forced by the rigidifying ethylene cross-bridge and show that two cis coordination cites are available for interaction with substrate and oxidant. The Cu complexes were used to determine kinetic stability under harsh acidic and high-temperature conditions, which revealed that the cyclam-based ligands provide superior stabilization with half-lives of many minutes or even hours in 5 M HCl at 50-90 °C. Cyclic voltammetry studies of the Fe and Mn complexes reveal reversible redox processes indicating stabilization of Fe2+/Fe3+ and Mn2+/Mn3+/Mn4+ oxidation states, indicating the likelihood of catalytic oxidation for these complexes. Finally, dye-bleaching experiments with methylene blue, methyl orange, and rhodamine B demonstrate efficient catalytic decolorization and allow selection of the most successful monomeric catalysts for copolymerization to produce future heterogeneous water purification materials.

Surface Engineering in Covalent Organic Polymers for High-Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are a promising energy storage technology due to their tempting high theoretical capacity and energy density. Nevertheless, the wastage of active materials that originates from the shuttling effect of polysulfides still hinders advancement of Li-S batteries. The effective design of cathode materials is extremely pivotal to solve this thorny problem. Herein, surface engineering in covalent organic polymers (COPs) has been performed to investigate the influence of pore wall polarity on the performance of COP-based cathodes used for Li-S batteries. With the assistance of experimental investigation and theoretical calculations, performance improvement by increasing pore surface polarity and a synergy effect of the polarized functionalities, along with nano-confinement effect of the COPs, are disclosed, to which the improved performance of Li-S batteries including outstanding Coulombic efficiency (99.0 %) and extremely low capacity decay (0.08 % over 425 cycles at 1.0 C) is attributed. This work not only enlightens the designable synthesis and applications of covalent polymers as polar sulfur hosts with high utilization of active materials, but also provides a feasible guide for the design of effective cathode materials for future advanced Li-S batteries.

Efficient removal of uranium (VI) from water by a hyper-cross-linked polymer adsorbent modified with polyethylenimine via phosphoramidate linkers

Practical adsorbents with high efficiency are essential to effectively treating wastewater. Herein, a novel porous uranium adsorbent (PA-HCP) having a considerable amount of amine and phosphoryl groups was designed and synthesized by grafting polyethyleneimine (PEI) on a hyper-cross-linked fluorene-9-bisphenol skeleton via phosphoramidate linkers. Furthermore, it was used to treat uranium contamination in the environment. PA-HCP exhibited a large specific surface area (up to 124 m2/g) and a pore diameter of 2.5 nm. Batch uranium adsorptions on PA-HCP were investigated methodically. PA-HCP demonstrated a uranium sorption capacity of >300 mg/g in the pH range of 4-10 (C0 = 60 mg/L, T = 298.15 K), with its maximum capacity reaching 573.51 mg/g at pH = 7. The uranium sorption process obeyed the pseudo-second-order model and fitted well with the Langmuir isothermal. In the thermodynamic experiments, uranium sorption on PA-HCP was revealed to be an endothermic, spontaneous process. Even in the presence of competing metal ions, PA-HCP exhibited excellent sorption selectivity for uranium. Additionally, excellent recyclability can be achieved after six cycles. Based on FT-IR and XPS measurements, both the PO and -NH2 (and/or -NH-) groups on PA-HCP contributed to efficient uranium adsorption as a result of the strong coordination between these groups and uranium. Furthermore, the high hydrophilicity of the grafted PEI improved the dispersion of the adsorbents in water and facilitated uranium sorption. These findings suggest that PA-HCP can be used as an efficient and economical sorbent to remove U(VI) from wastewater.

Machine-learning-assisted material discovery of oxygen-rich highly porous carbon active materials for aqueous supercapacitors

Porous carbons are the active materials of choice for supercapacitor applications because of their power capability, long-term cycle stability, and wide operating temperatures. However, the development of carbon active materials with improved physicochemical and electrochemical properties is generally carried out via time-consuming and cost-ineffective experimental processes. In this regard, machine-learning technology provides a data-driven approach to examine previously reported research works to find the critical features for developing ideal carbon materials for supercapacitors. Here, we report the design of a machine-learning-derived activation strategy that uses sodium amide and cross-linked polymer precursors to synthesize highly porous carbons (i.e., with specific surface areas > 4000 m²/g). Tuning the pore size and oxygen content of the carbonaceous materials, we report a highly porous carbon-base electrode with 0.7 mg/cm² of electrode mass loading that exhibits a high specific capacitance of 610 F/g in 1 M H₂SO₄. This result approaches the specific capacitance of a porous carbon electrode predicted by the machine learning approach. We also investigate the charge storage mechanism and electrolyte transport properties via step potential electrochemical spectroscopy and quasielastic neutron scattering measurements.

Sorption of Carbon Dioxide and Nitrogen on Porous Hyper-Cross-Linked Aromatic Polymers: Effect of Textural Properties, Composition, and Electrostatic Interactions

Porous hyper-cross-linked aromatic polymers are one of the emerging classes of porous organic polymers with the potential for industrial application. Four different porous polymeric materials have been prepared using different precursors (indole, pyrene, carbazole, and naphthalene), and the composition and textural properties were analyzed. The materials were characterized in detail using different physicochemical techniques like scanning electron microscopy, transmission electron microscopy, nitrogen adsorption at 77 K, Fourier transform infrared spectroscopy, X-ray diffraction, etc. The effect of textural properties and nitrogen species on carbon dioxide and nitrogen adsorption capacities and selectivity was studied and discussed. The carbon dioxide and nitrogen adsorption capacities were measured using a volumetric gas adsorption system. The adsorption data were fitted into different adsorption models, and the ideal absorbed solution theory was used to calculate adsorption selectivity. Among the studied samples, POP-4 shows the highest carbon dioxide and nitrogen adsorption capacities. While POP-1 shows maximum CO₂/N₂ selectivity of 78.0 at 298 K and 1 bar pressure. It is observed that ultra-micropores, which are present in the prepared materials but not measured during conventional surface area measurement via nitrogen adsorption at 77 K, play a very important role in carbon dioxide adsorption capacity and determining the carbon dioxide selectivity over nitrogen. Surface nitrogen also increases the CO₂ selectivity in the dual mode by increasing carbon dioxide adsorption via the acid-base interaction as well as by decreasing nitrogen adsorption due to N-N repulsion.

All-Round Enhancement in Zn-Ion Storage Enabled by Solvent-Guided Lewis Acid-Base Self-Assembly of Heterodiatomic Carbon Nanotubes

Designing zincophilic and stable carbon nanostructures is critical for Zn-ion storage with superior capacitive activity and durability. Here, we report solvent-guided Lewis acid-base self-assembly to customize heterodiatomic carbon nanotubes, triggered by the reaction between iron chloride and α,α'-dichloro-p-xylene. In this strategy, modulating the solvent-precursor interaction through the optimization of solvent formula stimulates differential thermodynamic solubilization, growth kinetics, and self-assembly behaviors of Lewis polymeric chains, thereby accurately tailoring carbon nanoarchitectures to evoke superior Zn-ion storage. Featured with open hollow interiors and porous tubular topologies, the solvent-optimized carbon nanotubes allow low ion-migration barriers to deeply access the built-in zincophilic sites by high-kinetics physical Zn²⁺/CF₃SO₃^- adsorption and robust chemical Zn²⁺ redox with pyridine/carbonyl motifs, which maximizes the spatial capacitive charge storage density. Thus, as-designed heterodiatomic carbon nanotube cathodes provide all-round improvement in Zn-ion storage, including a high energy density (140 W h kg^-1), a large current activity (100 A g^-1), and an exceptional long-term cyclability (100,000 cycles at 50 A g^-1). This study provides appealing insights into the solvent-mediated Lewis pair self-assembly design of nanostructured carbons toward advanced Zn-ion energy storage.

Naphthalene-Based Polymers as Catalytic Supports for Suzuki Cross-Coupling

In this work, for the first time, naphthalene (NA)-based polymers were synthesized by one-stage Friedel-Crafts crosslinking. The influence of NA functionalization by -OH, -SO₃H, and -NO₂ groups on the polymers' porosity and distribution of the catalytically active phase (Pd) was studied. Synthesized catalytic systems containing 1 wt.% of Pd either in the form of Pd(II) species or Pd(0) nanoparticles supported on NA-based polymers were tested in a model reaction of Suzuki cross-coupling between 4-bromoanisole and phenylboronic acid under mild reaction conditions (60 °C, ethanol-water mixture as a solvent). These novel catalysts demonstrated high efficiency with more than 95% of 4-bromoanisole conversion and high selectivity (>97%) for the target 4-methoxybiphenyl.

Rationalizing the formation of porosity in mechanochemically-synthesized polymers

In this study, we present a matrix of 144 mechanochemically-synthesized polymers. All polymers were constructed by the solvent-free Friedel-Crafts polymerization approach, employing 16 aryl-containing monomers and 9 halide-containing linkers, which were processed in a high-speed ball mill. This Polymer Matrix was utilized to investigate the origin of porosity in Friedel-Crafts polymerizations in detail. By examining the physical state, molecular size, geometry, flexibility, and electronic structure of the utilized monomers and linkers, we identified the most important factors influencing the formation of porous polymers. We analyzed the significance of these factors for both monomers and linkers based on the yield and specific surface area of the generated polymers. Our in-depth evaluation serves as a benchmark study for future targeted design of porous polymers by the facile and sustainable concept of mechanochemistry.

Amine functionalized benzene based hypercrosslinked polymer as an adsorbent for CO2/N2 adsorption

In this work, benzene based hypercrosslinked polymer (HCP) as an adsorbent was modified using amine group to enhance CO₂ uptake capability and selectivity. Based on BET analysis result, the HCP and the modified HCP provide surface area of 806 (m² g^-1) and micropore volume of 453 (m² g^-1) and 0.19 (cm³ g^-1) and 0.14 (cm³ g^-1), respectively. The CO₂ and N₂ gases adsorption were performed in a laboratory scale reactor at a temperature between 298 and 328 K and pressure up to 9 bar. The experimental data were evaluated using isotherm, kinetic and thermodynamic models to identify the absorbent behavior. The maximum CO₂ adsorption capacity at 298 K and 9 bar was obtained 301.67 (mg g^-1) for HCP and 414.41 (mg g^-1) for amine modified HCP. The CO₂ adsorption thermodynamic parameters assessment including enthalpy changes, entropy changes, and Gibbs free energy changes at 298 K were resulted - 14.852 (kJ mol^-1), - 0.024 (kJ mol^-1 K^-1), - 7.597 (kJ mol^-1) for HCP and - 17.498 (kJ mol^-1), - 0.029(kJ mol^-1 K^-1), - 8.9 (kJ mol^-1) for amine functionalized HCP, respectively. Finally, the selectivity of the samples were calculated at a CO₂/N₂ composition of 15:85 (v/v) and 43% enhancement in adsorption selectivity at 298 K was obtained for amine modified HCP.

Swellable Array Strategy Based on Designed Flexible Double Hypercross-linked Polymers for Synergistic Adsorption of Toluene and Formaldehyde

High-capacity adsorption and removal of complex volatile organic compounds (VOCs) from real-world environments is a tough challenge for researchers. Herein, a swellable array adsorption strategy was proposed to realize the synergistic adsorption of toluene and formaldehyde on the flexible double hypercross-linked polymers (FD-HCPs). FD-HCPs exhibited multiple adsorption sites awarded by a hydrophobic benzene ring/pyrrole ring and a hydrophilic hydroxyl structural unit. The array benzene ring, hydroxyl, and pyrrole N sites in FD-HCPs effectively captured toluene and formaldehyde molecules through π-π conjugation and electrostatic interaction and weakened their mutual competitive adsorption. Interestingly, the strong binding force of toluene molecules to the skeleton deformed the pore structure of FD-HCPs and generated new adsorption microenvironments for the other adsorbate. This behavior significantly improved the adsorption capacity of FD-HCPs for toluene and formaldehyde by 20% under multiple VOCs. Moreover, the pyrrole group in FD-HCPs greatly hindered H₂O molecule diffusion in the pore, thus efficiently weakening the competitive adsorption of H₂O toward VOCs. These fascinating properties enabled FD-HCPs to achieve synergistic adsorption for multicomponent VOC vapor under a highly humid environment and overcame single-species VOC adsorption properties on state-of-the-art porous adsorbents. This work provides the practical feasibility of synergistic adsorption to remove complex VOCs in real-world environments.

TM-Free and TM-Catalyzed Mechanosynthesis of Functional Polymers

Mechanochemically induced methods are commonly used for the depolymerization of polymers, including plastic and agricultural wastes. So far, these methods have rarely been used for polymer synthesis. Compared to conventional polymerization in solutions, mechanochemical polymerization offers numerous advantages such as less or no solvent consumption, the accessibility of novel structures, the inclusion of co-polymers and post-modified polymers, and, most importantly, the avoidance of problems posed by low monomer/oligomer solubility and fast precipitation during polymerization. Consequently, the development of new functional polymers and materials, including those based on mechanochemically synthesized polymers, has drawn much interest, particularly from the perspective of green chemistry. In this review, we tried to highlight the most representative examples of transition-metal (TM)-free and TM-catalyzed mechanosynthesis of some functional polymers, such as semiconductive polymers, porous polymeric materials, sensory materials, materials for photovoltaics, etc.

Ultrathin Hollow Co/N/C Spheres from Hyper-Crosslinked Polymers by a New Universal Strategy with Boosted ORR Efficiency

Porous carbon materials with hollow structure, on account of the extraordinary morphology, reveal fascinating prospects in lithium-ion batteries, electrocatalysis, etc. However, collapse in ultrathin carbon spheres due to insufficient rigidity in such thin materials obstructs further enhanced capability. Based on hyper-crosslinked polymers (HCPs) with sufficient pore structure and rigid framework, a new bottom-up strategy is proposed to construct SiO₂ @HCPs directly from aromatic monomers. Heteroatom and function groups can be facilely introduced to the skeleton. The thickness of HCPs' wall can be tuned from 9 to 20 nm, which is much thinner than that of hollow sphere synthesized by the traditional method, and the sample with a thickness of 20 nm shows the highest surface area of 1633 m² g^-1 . The oxygen reduction reaction is conducted and the CoNHCS electrocatalysts with an ultrathin thickness of 5 nm display higher half-wave potential than those of bulk samples, even better than commercial Pt/C electrode. On account of the hollow structure, the relative current density loss of electrocatalysts is only 4.1% in comparison with 27.7% in Pt/C electrode during the 15 000 s test, indicating an obvious higher long-term stability. The new strategy to construct hollow HCPs may shed light on efficient chemical catalysis, drug delivery, and electrocatalysis.

Construction of a nano dispersed Cr/Fe-polycrystalline sensor via high-energy mechanochemistry for simultaneous electrochemical determination of dopamine and uric acid

A bimetallic polycrystalline sensor (Cr/Fe-SNCM) having nanosized and high dispersion was designed and used for the electrochemical simultaneous determination of dopamine (DA) and uric acid (UA). Catalytic nanosized Cr/Fe were highly anchored on N/S/O-contained porous carbon with high dispersion and polycrystalline Cr/Fe via energetic mechanochemical method and high-temperature carbonization. The obtained Cr/Fe-SNCM exhibited high graphitized carbon supporter and endowed high electron transport and signal output for the whole sensor. Moreover, highly dispersed Cr/Fe sites and the polycrystalline form (metal-N/S/O) efficiently enhanced the catalytic reaction, leading to a limits of detection (based on the 3σ/m criterion) of 25.8 and 22.5 nM for DA and UA, respectively. This is 1-2 orders of magnitude lower than many state-of-the-art reported sensors. The Cr/Fe-SNCM_1.0 sensor exhibited wide working range (0.1 to 10.0 μM), high recovery (96-103%) and low relative standard deviation (RSD = 3.2-4.7%) for DA and UA in real serum samples, possessing high significance for practical large-scale applications.

Fabrication, Facilitating Gas Permeability, and Molecular Simulations of Porous Hypercrosslinked Polymers Embedding 6FDA-Based Polyimide Mixed-Matrix Membranes

Novel polymers applied in economic membrane technologies are a perennial hot topic in the fields of natural gas purification and O₂ enrichment. Herein, novel hypercrosslinked polymers (HCPs) incorporating 6FDA-based polyimide (PI) MMMs were prepared via a casting method for enhancing transport of different gases (CO₂, CH₄, O₂, and N₂). Intact HCPs/PI MMMs could be obtained due to good compatibility between the HCPs and PI. Pure gas permeation experiments showed that compared with pure PI film, the addition of HCPs effectively promotes gas transport, increases gas permeability, and maintains ideal selectivity. The permeabilities of HCPs/PI MMMs toward CO₂ and O₂ were as high as 105.85 Barrer and 24.03 Barrer, respectively, and the ideal selectivities of CO₂/CH₄ and O₂/N₂ were 15.67 and 3.00, respectively. Molecular simulations further verified that adding HCPs was beneficial to gas transport. Thus, HCPs have potential utility in fabrication of MMMs for facilitating gas transport in the fields of natural gas purification and O₂ enrichment.

Emerging Materials for Interfacial Solar-Driven Water Purification

Solar-driven water purification is considered as an effective and sustainable technology for water treatment using green solar energy. One major goal for practical applications is to improve the solar evaporation performance by the design of novel photothermal materials, with optimized heat localization and water transport pathways to achieve reduced energy consumption for water vaporization. Recently, some emerging materials like polymers, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and also single molecules were employed to construct novel solar evaporation systems. In this minireview, we present an overview of the recent efforts on materials development for water purification systems. The state-of-the-art applications of these emerging materials for solar-driven water treatment, including desalination, wastewater purification, sterilization and energy production, are also summarized.

Suspension polymerization for synthesis of new hypercrosslinked polymers nanoparticles for removal of copper ions from aqueous solutions

Novel hypercrosslinked polymers nanoparticles (HCPNs) were designed by suspension polymerization technique with high surface area as well as HCPNs with functional groups have the affinity to removal of copper ions from aqueous solutions. Two HCPNs were synthesized through a two-step reaction, initially including the suspension polymerization of N-methacryloxytetrachlorophthalimide (NMTPA) with divinyl benzene (DVB) to give poly(NMTPA-co-DVB) and followed by the treatment of poly(NMTP-co-DVB) with triethylenetetramine (TETA) to give HCPNs (1) and with tetraethylenepentamine (TEPA) to give HCPNs (2). Using scanning electron microscopy and transmission electron microscopy, the surface morphology of the particles of the synthesized HCPNs was detected, and also, the particle size was measured. Also, the chemical structures of the synthesized compounds were illustrated by Fourier transform infrared spectroscopy and 1H-nuclear magnetic resonance (1H NMR). Thermal stability of the synthesized HCPNs was characterized by thermogravimetric analysis. The results illustrated that the particle size of the synthesized HCPNs is in range of 25–50 nm. The synthesized HCPNs compounds were reported for the separation of copper ions from wastewater, in which the results showed a very good affinity for these compounds for separation of copper ions from wastewater.

Synthesis, Characterization, and Gas Adsorption Performance of Amine-Functionalized Styrene-Based Porous Polymers

In recent years, porous materials have been extensively studied by the scientific community owing to their excellent properties and potential use in many different areas, such as gas separation and adsorption. Hyper-crosslinked porous polymers (HCLPs) have gained attention because of their high surface area and porosity, low density, high chemical and thermal stability, and excellent adsorption capabilities in comparison to other porous materials. Herein, we report the synthesis, characterization, and gas (particularly CO₂) adsorption performance of a series of novel styrene-based HCLPs. The materials were prepared in two steps. The first step involved radical copolymerization of divinylbenzene (DVB) and 4-vinylbenzyl chloride (VBC), a non-porous gel-type polymer, which was then modified by hyper-crosslinking, generating micropores with a high surface area of more than 700 m² g^-1. In the following step, the polymer was impregnated with various polyamines that reacted with residual alkyl chloride groups on the pore walls. This impregnation substantially improved the CO₂/N₂ and CO₂/CH₄ adsorption selectivity.

iClick synthesis of network metallopolymers

Described is an approach to preparing the first iClick network metallopolymers with porous properties. Treating digoldazido complex 2-AuN3 with trigoldacetylide 3-AuPPh3 or 3-AuPEt3, trialkyne 3-H, tetragoldacetylide 4-AuPPh3, or tetraalkyne 4-H in CH₂Cl₂ affords five iClick network metallopolymers 5-AuPPh3, 5-AuPEt3, 5-H, 6-AuPPh3, and 6-H. Confirmation of the iClick network metallopolymers comes from FTIR, ¹³C solid-state cross-coupling magic angle spinning (CPMAS) NMR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and nitrogen and CO₂ sorption analysis. Employing model complexes 7-AuPPh3, 7-AuPEt3, 7-H, 8-AuPPh3, and 8-H provides structural insights due to the insolubility of iClick network metallopolymers.

Porous Polymers Containing Metallocalix[4]arene for the Extraction of Tobacco-Specific Nitrosamines

We designed porous polymers with a tungsten-calix[4]arene imido complex as the nitrosamine receptor for the efficient extraction of tobacco-specific nitrosamines (TSNAs) from water. The interaction between the metallocalix[4]arene and the TSNA, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (nicotine-derived nitrosamine ketone, NNK) was investigated. We found that the incorporation of the nitrosamine receptor into porous polymers increased their selectivity toward NNK over nicotine. The polymer with an optimal ratio of calixarene-containing and porosity-inducing building blocks showed a high maximum adsorption capacity of up to 203 mg/g toward NNK under sonication, which was among the highest values reported. The adsorbed NNK could be removed from the polymer by soaking it in acetonitrile, enabling the adsorbent to be reused. A similar extraction efficiency to that under sonication could be achieved using the polymer-coated magnetic particles under stirring. We also proved that the material could efficiently extract TSNAs from real tobacco extract. This work not only provides an efficient material for the extraction of TSNAs but also offers a design strategy for efficient adsorbents.

BINOL-Containing Chiral Porous Polymers as Platforms for Enantiorecognition

The enantioselective discrimination of racemic compounds can be achieved through the design and preparation of a new family of chiral conjugated BINOL-porous polymers (CBPPs) from enantiopure (R)- or (S)-BINOL derivatives and 1,3,5-tris(4-phenylboronic acid)benzene or 1,3,5-tris(4-ethynylphenyl)benzene, 1,3,5-triethynyl-2,4,6-trifluorobenzene, and tetra(4-ethynylphenyl)methane as comonomers following Suzuki-Miyaura and Sonogashira-Hagihara carbon-carbon coupling approaches. The obtained CBPPs show high thermal stability, a good specific surface area, and a robust framework and can be applied successfully in the fluorescence recognition of enantiomers of terpenes (limonene and α-pinene) and 1-phenylethylamine. Fluorescence titration of CBPPs-OH in acetonitrile shows that all Sonogashira hosts exhibit a preference for the (R)-enantiomer over the (S)-enantiomer of 1-phenylethylamine, the selectivity being much higher than that of the corresponding BINOL-based soluble system used as a reference. However, the Suzuki host reveals a preference toward (S)-phenylethylamine. Regarding the sensing of terpenes, only Sonogashira hosts show enantiodifferentiation with an almost total preference for the (S)-enantiomer of limonene and α-pinene. Based on the computational simulations and the experimental data, with 1-phenylethylamine as the analyte, chiral recognition is due to the distinctive binding affinities resulting from N···H-O hydrogen bonds and the π-π interaction between the host and the guest. However, for limonene, the geometry of the adsorption complex is mostly governed by the interaction between the hydroxyl group of the BINOL unit and the C═C bond of the iso-propenyl fragment. The synthetic strategy used to prepare CBPPs opens many possibilities to place chiral centers such as BINOL in porous polymers for different chiral applications such as enantiomer recognition.

Machine Learning in the Development of Adsorbents for Clean Energy Application and Greenhouse Gas Capture

Addressing climate change challenges by reducing greenhouse gas levels requires innovative adsorbent materials for clean energy applications. Recent progress in machine learning has stimulated technological breakthroughs in the discovery, design, and deployment of materials with potential for high-performance and low-cost clean energy applications. This review summarizes basic machine learning methods-data collection, featurization, model generation, and model evaluation-and reviews their use in the development of robust adsorbent materials. Key case studies are provided where these methods are used to accelerate adsorbent materials design and discovery, optimize synthesis conditions, and understand complex feature-property relationships. The review provides a concise resource for researchers wishing to use machine learning methods to rapidly develop effective adsorbent materials with a positive impact on the environment.

Hypercrosslinking porous polymer layers on TiO2-graphene photocatalyst: Enhanced adsorption of water pollutants for efficient degradation

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the degradation of organic pollutants in water without chemical additives, but the low specific surface area and adsorption capacity of common photocatalysts restricts the surface reactions with the contaminants. Herein, we hypercrosslinked polymer layers on TiO₂-graphene surface to enlarge the specific surface area from 136 to 988 m²/g, leading to a high adsorption capacity of sulfadiazine as 54.3 mg/g, which is 15.5 times that of TiO₂-graphene (3.5 mg/g). The adsorption kinetics reveals the combination of physical and chemical adsorption by porous benzene-based polymer for sulfadiazine enrichment. Besides, the polymer layers with broad light absorption enable the composite to function efficiently as visible-light-driven photocatalysts. Thus, the as-designed composite exhibits excellent performance for sulfadiazine removal by integrating the adsorptive and photocatalytic processes, especially for the diluted sulfadiazine solution. More importantly, the porous polymer layer can function as a filter for weakening the interference of TiO₂ surface with the natural matters from complex water matrices. Based on the identification of dominant reactive species, the possible attacking pathway and the sulfadiazine subsequent degradation are presented. Further, the enhanced adsorption and photodegradation efficiency can also be achieved for the removal of other typical pollutants such as 4-chlorophenol and methylene blue. This study highlights an adsorption-enhanced-degradation mechanism for water pollutants that can direct the design of high-performance photocatalysts under visible light.

Facile synthesis of magnetic hypercrosslinked polymer for the magnetic solid-phase extraction of benzoylurea insecticides from honey and apple juice samples

In this work, a novel knitting aromatic polymer (KAP) was fabricated for the first time by knitting ferrocene with 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene via Friedel-Crafts reaction, and then the KAP was magnetically functionalized with Fe₃O₄ nanoparticles to produce a magnetic KAP (M-KAP). Combining M-KAP based magnetic solid-phase extraction with high performance liquid chromatography-ultraviolet detection, a simple and sensitive method was developed for simultaneous determination of six benzoylurea insecticides (BUs) in honey and apple juice samples. In the optimized conditions, a good linearity for the BUs existed in the range of 1.67-1000 ng g^-1 for honey sample and 0.500-100.0 ng mL^-1 for apple juice sample. The limits of detection were 0.500-1.50 ng g^-1 and 0.150-0.400 ng mL^-1 for honey and apple juice sample, respectively. Satisfactory recoveries were in the range of 85.5-105.5% with RSDs ≤ 8.3%. The developed method demonstrated an excellent practicability for sensitive analysis of the BUs.

Investigation of the Flame Retardant Properties of High-Strength Microcellular Flame Retardant/Polyurethane Composite Elastomers

Flame retardants (FRs) often reduce the mechanical properties of polymer materials, and FR/microcellular polyurethane elastomer (MPUE) composite materials have not been systemically studied. Hence, we conducted this study on FR/MPUE composites by using multiple liquid FRs and/or expandable graphite (EG). Compared with liquid flame retardants, the LOI of an expandable graphite/dimethyl methylphosphonate (EG/DMMP) (3:1) combination was significantly increased (~36.1%), and the vertical combustion grade reached V-0 without a dripping phenomenon. However, the corresponding tensile strength was decreased by 17.5%. With the incorporation of EG alone, although the corresponding LOI was not a match with that of DMMP/EG, there was no droplet phenomenon. In addition, even with 15 wt% of EG, there was no significant decline in the tensile strength. Cone calorimeter test results showed that PHRR, THR, PSPR, and TSR were significantly reduced, compared to the neat MPUE, when the EG content surpassed 10 wt%. The combustion process became more stable and thus the fire risk was highly reduced. It was found that flame retardancy and mechanical properties could be well balanced by adding EG alone. Our proposed strategy for synthesizing FR/MPUE composites with excellent flame retardancy and mechanical properties was easy, effective, low-cost and universal, which could have great practical significance in expanding the potential application fields of MPUEs.

Imine and imine-derived linkages in two-dimensional covalent organic frameworks

Covalent organic frameworks (COFs) are porous crystalline polymers that result from the formation of covalent bonds between precisely assembled organic units. Linkage chemistry is a crucial factor in the controllable synthesis and resulting physicochemical properties of COFs. Imine linkages are popular in the formation of polyfunctional two-dimensional (2D) COFs because they are formed easily with structural and functional diversity. There has been much recent interest in expanding beyond this to COFs with imine-derived linkages. This review highlights the development of chemistry to modify and prepare derivatives of imines within 2D COFs. We discuss the derivation of imine bonds via covalent and noncovalent bonding and the properties and potential applications of the resulting materials in order to provide a better understanding of the relationship between covalent linkages and overall performance for 2D COF materials.

Fluorescent porous organic polymers for detection and adsorption of nitroaromatic compounds

A fluorescent porous organic polymer (FPOP) with strong fluorescence and tunable emission colors, was synthesized through a simple cost-effective method via Scholl coupling reaction. Experiments proved the stability and excellent detection and adsorption ability, and microporous nature of the material. Luminescence of FPOP was quenched when addition of nitroaromatic compounds. The properties along with large-scale and low-cost preparation make these FPOP potential candidates for fluorescence detection of nitroaromatic compounds. Additionally, FPOP shows higher adsorption capacity and rate than other reported adsorbents, and has the possibility of being an effective adsorbent for industrial usage. Moreover, a fluorescent test paper was further developed and is found to be sensitive to 10^-8 M level, complete with a rapid response time and visual detection. This newly developed strategy may open up an avenue for exploring porous polymers, particularly those with a strong fluorescence, for the large-scale fabrication of FPOP for various advanced applications.