Hypercrosslinked porous polymer materials: design, synthesis, and applications

Breakthrough applications of porous organic materials for membrane-based CO2 separation: a review

Over the last decades, porous organic materials (POMs) have been extensively employed in various industrial approaches including gas separation, catalysis and energy production due to possessing indisputable advantages like great surface area, high permeability, controllable pore size, appropriate functionalization and excellent processability compared to traditional substances like zeolites, Alumina and polymers. This review presents the recent breakthroughs in the multifunctional POMs for potential use in the membrane-based CO2 separation. Some examples of highly-selective membranes using multifunctional POMs are described. Moreover, various classifications of POMs following with their advantages and disadvantages in CO2 separation processes are explained. Apart from reviewing the state-of-the-art POMs in CO2 separation, the challenges/limitations of POMs with tailored structures for reasonable application are discussed.

Polyoxometalate-loaded hyper-crosslinked nanoparticles as a Pickering interfacial catalyst for solvent-free epoxidation of allyl chloride under static conditions

Epoxidation of allyl chloride and hydrogen peroxide (H2O2) carried out in heterogeneous catalytic systems suffer from poor reaction efficiency due to their heavy mass transfer resistance present at the liquid-liquid interface. Pickering interfacial catalysis (PIC) provides an elegant solution by involving the design of amphiphilic heterogeneous catalysts, which can act as emulsifiers simultaneously. In this study, interface-active polyoxometalate-loaded hyper-crosslinked nanoparticles (HCNPs) were designed. The structural properties of materials were characterized in detail by elemental analysis, Zeta potential, ICP-OES, SEM, TEM, BET, FT-IR, TGA, and XPS. The prepared nanoparticles can build efficient W/O PIC systems with allyl chloride and H2O2. Systematic experiments indicate that catalysts' surface properties, catalyst dosage, and water/oil volume ratio significantly affect the PIC system's catalytic activity and emulsion properties. Moreover, this PIC system maintains high stability after the reaction and can be reused for at least 8 cycles. Excitingly, these interface-active HCNPs can also efficiently promote allyl chloride epoxidation in the absence of solvent and external stirring, illustrating that this approach holds great potential for developing catalytic systems suitable for multiphase reactions.

Construction of hydroxyl-functionalized hyper-crosslinked networks from polyimide for highly efficient iodine adsorption

The rapid development of nuclear energy posed a great threat to the environment and human health. Herein, two hydroxyl-functionalized hyper-crosslinked polymers (PIHCP-1 and PIHCP-2) containing different electron active sites have been synthesized via Friedel-Crafts alkylation reaction of the polyimides. The resulting polymers showed a micro/mesoporous morphology and good thermal and chemical stability. Rely on the high porosity and multi-active sites, the PIHCPs show an ultrahigh iodine uptake capacity reached 6.73 g g-1 and the iodine removal efficiency from aqueous solution also reaches 99.7%. Kinetic analysis demonstrates that the iodine adsorption on PIHCPs was happened on the heterogeneous surfaces in the form of multilayer chemisorption. Electrostatic potential (ESP) calculation proves the great contribution of hydroxyl groups on the iodine capture performance. In addition, the iodine capture efficiency of both adsorbents can be maintained over 91% after four cyclic experiments which ensures their good recyclability for further practical applications.

Recent progress in electrode materials for micro-supercapacitors

Micro-supercapacitors (MSCs) stand out in the field of micro energy storage devices due to their high power density, long cycle life, and environmental friendliness. The key to improving the electrochemical performance of MSCs is the selection of appropriate electrode materials. To date, both the composition and structure of electrode materials in MSCs have become a hot research topic, and it is urgent to compose a review to highlight the most important research achievements, major challenges, opportunities, and encouraging perspectives in this field. In this review, research background of MSCs is first reviewed followed by their working principles, structural classifications, and physiochemical and electrochemical characterization techniques. Next, various materials and preparation methods are summarized, and the relationship between the MSC performance and structure and composition of materials are discussed in depth. Finally, this review provides a comprehensive suggestion on accelerating the development of electrode materials to facilitate the commercialization of MSCs.

Crystalline porous organic salts

Crystalline porous organic salts (CPOSs), formed by the self-assembly of organic acids and organic bases through ionic bonding, possess definite structures and permanent porosity and have rapidly emerged as an important class of porous organic materials in recent years. By rationally designing and controlling tectons, acidity/basicity (pKa), and topology, stable CPOSs with permanent porosity can be efficiently constructed. The characteristics of ionic bonds, charge-separated highly polar nano-confined channels, and permanent porosity endow CPOSs with unique physicochemical properties, offering extensive research opportunities for exploring their functionalities and application scenarios. In this review, we systematically summarize the latest progress in CPOS research, describe the synthetic strategies for synthesizing CPOSs, delineate their structural characteristics, and highlight the differences between CPOSs and hydrogen-bonded organic frameworks (HOFs). Furthermore, we provide an overview of the potential applications of CPOSs in areas such as negative linear compression (NLC), proton conduction, rapid transport of CO2, selective and rapid transport of K+ ions, atmospheric water harvesting (AWH), gas sorption, molecular rotors, fluorescence modulation, room-temperature phosphorescence (RTP) and catalysis. Finally, the challenges and future perspectives of CPOSs are presented.

A nanoporous organic polymer using 1, 3-dibromoadamantane as a crosslinker for adsorption/separation of benzene and cyclohexane

The development of nanoporous organic polymers with cycloaliphatic components for effective benzene (Bz) and cyclohexane (Cy) adsorption/separation poses a significant challenge. This work focuses on synthesizing NOP-Ad-1, a nanoporous organic polymer derived from a Friedel-Crafts reaction between cycloaliphatic 1,3-dibromadantane and aromatic hexaphenylbenzene. At 298 K and P/P0 = 0.95, NOP-Ad-1 can uptake 989 mg g-1 benzene and 441 mg g-1 cyclohexane. Moreover, as the benzene vapor ratio increased from 20% to 80%, the Bz/Cy selectivity of NOP-Ad-1 gradually decreased from 1.75 to 1.24. These findings highlight the potential application of NOP-Ad-1 in the adsorption/separation of Bz/Cy mixtures.

Synthesis of cyano and ionic dual-functional hypercrosslinked porous polymer for effective adsorption and detection of endocrine disrupting chemicals in milk matrix

Endocrine disrupting chemicals (EDCs) can interfere with the normal function of endocrine system, posing serious risk to human health. The monitoring of EDCs in foods is of great importance to ensure food security. Herein, a cyano and ionic dual-functionalized hypercrosslinked porous polymer (CN-iHCP) was designed and prepared for the first time through hyper-crosslink of 1-(4-cyanophenyl)imidazole and 1,4-bis(chloromethyl)benzene. The adsorption mechanism mainly involves electrostatic interaction, hydrogen bonding and π-π stacking interaction. A sensitive analytical method for simultaneous detection of the four phenolic EDCs was established by coupled CN-iHCP based solid-phase extraction with high performance liquid chromatography. Under optimal conditions, the target EDCs exhibited good linearity with coefficient r > 0.993 and high enrichment factors of 164-243. The detection limits (S/N = 3) of EDCs were 0.20-0.50 ng mL-1 for milk sample. The extraction recoveries for the spiked milk samples were in the range of 85.5%- 116.0%. This work not only highlights the CN-iHCP as a promising adsorbent to efficiently enrich EDCs and other pollutants, but also provides a new strategy for the functionalization of HCP for wide applications.

Azo-Linked Porous Polycalix[n]arenes for the Efficient Removal of Organic Micropollutants from Water

Developing novel porous adsorbents for efficient wastewater treatment is significant to the environment protection. Herein, three porous polycalix[n]arenes (n = 4, 6, and 8) which had varying cavity sizes of the macrocycle (Azo-CX4P, Azo-CX6P, and Azo-CX8P) were prepared under mild conditions and tested for their potential application in water purification. Azo-CX8P with a larger cavity size of the macrocycle outperformed Azo-CX4P and Azo-CX6P in screening studies involving a range of organic micropollutants. It was proved that Azo-CX8P was especially efficient in the removal of cationic dyes because of its high negative surface charge. In terms of the adsorption of Rhodamine B with Azo-CX8P, the pseudo-second-order rate constant reaches 5.025 g·mg-1·min-1 with the maximum adsorption capacity being 1345 mg·g-1. These values are significantly higher compared with those recorded for most adsorbents. In addition, the easily prepared Azo-CX8P can be reused at least six times without a loss of the adsorption efficiency, demonstrating its potential use in water purification.

Rigidity with Flexibility: Porous Triptycene Networks for Enhancing Methane Storage

In the pursuit of advancing materials for methane storage, a critical consideration arises given the prominence of natural gas (NG) as a clean transportation fuel, which holds substantial potential for alleviating the strain on both energy resources and the environment in the forthcoming decade. In this context, a novel approach is undertaken, employing the rigid triptycene as a foundational building block. This strategy is coupled with the incorporation of dichloromethane and 1,3-dichloropropane, serving as rigid and flexible linkers, respectively. This combination not only enables cost-effective fabrication but also expedites the creation of two distinct triptycene-based hypercrosslinked polymers (HCPs), identified as PTN-70 and PTN-71. Surprisingly, despite PTN-71 manifesting an inferior Brunauer-Emmett-Teller (BET) surface area when compared to the rigidly linked PTN-70, it showcases remarkably enhanced methane adsorption capabilities, particularly under high-pressure conditions. At a temperature of 275 K and a pressure of 95 bars, PTN-71 demonstrates an impressive methane adsorption capacity of 329 cm3 g-1. This exceptional performance is attributed to the unique flexible network structure of PTN-71, which exhibits a pronounced swelling response when subjected to elevated pressure conditions, thus elucidating its superior methane adsorption characteristics. The development of these advanced materials not only signifies a significant stride in the realm of methane storage but also underscores the importance of tailoring the structural attributes of hypercrosslinked polymers for optimized gas adsorption performance.

Palladium(II)-immobilized Triptycene based Hypercrosslinked Polymers: An Efficient, Green, and Reusable Heterogenous Catalyst for Suzuki-Miyaura Cross-coupling Reaction

The Suzuki-Miyaura cross-coupling (SMCC) involves the coupling of organohalides and organoboron molecules in the presence of Pd(II)-based catalysts. Often SMCC reactions employ homogenous catalysts. However, such homogenous SMCC reactions are associated with certain limitations which has motivated design of effective and sustainable Pd(II)-based heterogeneous catalytic systems. Herein, we report a systematic development of a Pd(II)-immobilized and triptycene based ionic hyper crosslinked polymer (Pd@TP-iHCP) and explored its application as a heterogeneous catalyst for SMCC reaction. Pd@TP-iHCP has ample N-heterocyclic carbene (NHC) pendants that anchor Pd(II) centres on the polymeric matrix. Pd@TP-iHCP was characterized satisfactorily using FT-IR, 13 C CP-MAS NMR, BET surface area analysis, SEM, EDX and HRTEM. The performance of Pd@TP-iHCP as a heterogeneous catalyst for SMCC reactions was explored using various combinations of aryl boronic acids and aryl halides. Experimental results show that Pd@TP-iHCP is associated with a moderately high surface area. It is an efficient catalyst for SMCC (in aqueous media) with a modest loading of 0.8 mol % Pd(II)-catalyst since high yields of the expected products were obtained in shorter time intervals. Pd@TP-iHCP also features excellent stability and catalyst recyclability since it could be re-used for several cycles without any significant decrease in catalytic efficiency.

A chitin-based magnetic hyper-cross-linked polymer for highly efficient enrichment of neonicotinoids in lemon juice and tomatoes

A chitin-based magnetic hyper-cross-linked polymer (labeled as Ch-MHCP) has been successfully synthesized and utilized for highly-effective solid-phase extraction of neonicotinoid insecticides (NEOs). The extraction capability of Ch-MHCP for four common NEOs is higher than that of four commercial sorbents including octadecyl-silane C18, oasis hydrophilic/lipophilic balanced sorbent, oasis mixed anion sorbent and poly-phenylacetic mixed anion sorbent. The large number of hydroxyl and amide groups as well as benzene rings in Ch-MHCP allow the H-bond and π-π* interaction to be the principal adsorption mechanism of Ch-MHCP for NEOs. Besides, polar interaction was also involved in the adsorption process. In combination of Ch-MHCP based extraction technique with high-performance liquid chromatography, a novel analytical method for sensitive detection of NEOs in lemon juice and tomatoes has been established. At optimal conditions, wide linear ranges were obtained to be 0.20-100 ng mL-1 for lemon juice and 0.80-1000 ng g-1 for tomatoes. The detection limits were 0.06-0.12 ng mL-1 for lemon juice and 0.24-0.60 ng g-1 for tomatoes. This work not only provides a powerful tool for simultaneously detecting four NEOs in lemon juice and tomatoes, but also offers a new insight into the preparation of bio-based magnetic sorbents for adsorption/removal of pollutants.

Thiophene-based porphyrin polymers for Mercury (II) efficient removal in aqueous solution

Development of novel sulf-functionalized porous organic polymers (POPs) for Mercury (II) (Hg2+) removal is of great significant, but the adsorbents always suffered by the low adsorption capacity, stability, and efficiency for the reason that the common construction of functionalized POPs from the functionalized monomers or post-functionalization of the POPs always sacrifice the porosity. In this paper, porphyrin-based POPs with different heteroatoms were constructed through the aldehyde monomer (benzene, 2,5-thiophenedicarboxaldehyde and thieno[3,2-b]thiophene-2,5-dicarboxaldehyde) and pyrrole according to the Adler-Longo method. In this way, nitrogen (N) in pyrrole and sulfur (S) in thiophene structures were embed into the backbone structure of the polymers. The functional structures not only act as the linking building block into the stable cross-linking structure, but also offer abundant uncovered functional sites for Hg2+ adsorption, resulting the porphyrin-based POPs high Hg2+ capacity (1049 mg/g), removal efficiency (more than 99.9%), good reusability and selectivity for its highest heteroatoms contents. The adsorption mechanism confirmed the cooperative coordination of N in porphyrin and S in thiophene with Hg2+. This work confirmed the functional groups play more important role in heavy metal adsorption, and the embedded functional sites into backbone also promotes the stability and the adsorption performance.

Single-Component Hydrophilic Terpolymer Thin Film Systems for Imparting Surface Chemical Versatility on Various Substrates

We demonstrate a single-component hydrophilic photocrosslinkable copolymer system that incorporates all critical functionalities into one chain. This design allows for the creation of uniform functional organic coatings on a variety of substrates. The copolymers were composed of a poly(ethylene oxide)-containing monomer, a monomer that can release a primary amine upon UV light, and a monomer with reactive epoxide or cyclic dithiocarbonate with a primary amine. These copolymers are easily incorporated into the solution-casting process using polar solvents. Furthermore, the resulting coating can be readily stabilized through UV light-induced crosslinking, providing an advantage for controlling the surface properties of various substrates. The photocrosslinking capability further enables us to photolithographically define stable polymer domains in a desirable region. The resulting copolymer coatings were chemically versatile in immobilizing complex molecules by (i) post-crosslinking functionalization with the reactive groups on the surface and (ii) the formation of a composite coating by mixing varying amounts of a protein of interest, i.e., fish skin gelatin, which can form a uniform dual crosslinked network. The number of functionalization sites in a thin film could be controlled by tuning the composition of the copolymers. In photocrosslinking and subsequent functionalizations, we assessed the reactivity of the epoxide and cyclic dithiocarbonate with the generated primary amine. Moreover, the orthogonality of the possible reactions of the presented reactive functionalities in the crosslinked thin films with complex molecules is assessed. The resulting copolymer coatings were further utilized to define a hydrophobic surface or an active surface for the adhesion of biological objects.

An Overview of Heterogeneous Catalysts Based on Hypercrosslinked Polystyrene for the Synthesis and Transformation of Platform Chemicals Derived from Biomass

Platform chemicals, also known as chemical building blocks, are substances that serve as starting materials for the synthesis of various value-added products, which find a wide range of applications. These chemicals are the key ingredients for many fine and specialty chemicals. Most of the transformations of platform chemicals are catalytic processes, which should meet the requirements of sustainable chemistry: to be not toxic for humans, to be safe for the environment, and to allow multiple reuses of catalytic materials. This paper presents an overview of a new class of heterogeneous catalysts based on nanoparticles of catalytically active metals stabilized by a polymer matrix of hypercrosslinked polystyrene (HPS). This polymeric support is characterized by hierarchical porosity (including meso- and macropores along with micropores), which is important both for the formation of metal nanoparticles and for efficient mass transfer of reactants. The influence of key parameters such as the morphology of nanoparticles (bimetallic versus monometallic) and the presence of functional groups in the polymer matrix on the catalytic properties is considered. Emphasis is placed on the use of this class of heterogeneous catalysts for the conversion of plant polysaccharides into polyols (sorbitol, mannitol, and glycols), hydrogenation of levulinic acid, furfural, oxidation of disaccharides, and some other reactions that might be useful for large-scale industrial processes that aim to be sustainable. Some challenges related to the use of HPS-based catalysts are addressed and multiple perspectives are discussed.

Revealing the role of hydrogen bond coupling structure for enhanced performance of the solid-state electrolyte

Achieving practical applications of PEO-based composite solid electrolyte (CPE) batteries requires the precise design of filler structures at the molecular level to form stable composite interfacial phases, which in turn improve the conductivity of Li+ and inhibit the nucleation growth of lithium dendrites. Some functional fillers suffer from severe agglomeration due to poor compatibility with the polymer base or grain boundary migration, resulting in limited improvement in cell performance. In this paper, ILs@KAP1 is reported as a filler to enhance the performance of PEO-based batteries. Thereinto, the hypercrosslinked phosphorus ligand polymer-containing KAP1, designed at the molecular level, has an abundant porous structure, hydrogen bonding network, and a rigid skeleton structure of benzene rings. These can be used both to improve the flammability with PEO-based and to reduce the crystallinity of the polymer electrolyte. Ionic liquids (ILs) are encapsulated in the nanochannels of KAP1, and thus a 3D Li+ conducting framework could be formed. In this case, it could not only facilitate the wettability of the contact interface with the electrode, significantly promoting its compatibility and providing a fast Li+ transport path, but also facilitate the formation of LiF, Li3N and Li2O rich SEI components, further fostering the uniform deposition/exfoliation of lithium. The LFP||CPE||Li battery assembled with ILs@KAP1-PEO-CPE has a high initial discharge specific capacity about 156 mAh/g at 1C and a remaining capacity about 121.8 mAh/g after 300 cycles (capacity retention of 78.07%).

Directly Knitted Hierarchical Porous Organometallic Polymer-Based Self-Supported Single-Site Catalyst for CO2 Hydrogenation in Water

In recent times, heterogenization of homogeneous molecular catalysts onto various porous solid support structures has attracted significant research focus as a method for combining the advantages of both homogeneous as well as heterogeneous catalysis. The design of highly efficient, structurally robust and reusable heterogenized single-site catalysts for the CO2 hydrogenation reaction is a critical challenge that needs to be accomplished to implement a sustainable and practical CO2 -looped renewable energy cycle. This study demonstrated a heterogenized catalyst [Ir-HCP-(B/TPM)] containing a molecular Ir-abnormal N-heterocyclic carbene (Ir-aNHC) catalyst self-supported by hierarchical porous hyper-crosslinked polymer (HCP), in catalytic hydrogenation of CO2 to inorganic formate (HCO2 - ) salt that is a prospective candidate for direct formate fuel cells (DFFC). By employing this unique and first approach of utilizing a directly knitted HCP-based organometallic single-site catalyst for CO2 -to-HCO2 - in aqueous medium, extremely high activity with a single-run turnover number (TON) up to 50816 was achieved which is the highest so far considering all the heterogeneous catalysts for this reaction in water. Additionally, the catalyst featured excellent reusability furnishing a cumulative TON of 285400 in 10 cycles with just 1.6 % loss in activity per cycle. Overall, the new catalyst displayed attributes that are important for developing tangible catalysts for practical applications.

Amorphous porous organic polymers containing main group elements

Amorphous porous organic polymers (aPOPs) are a type of highly crosslinked polymers. These polymers are generally constructed from rigid organic building blocks, which have become an important subclass of POPs with diverse applications. In the early stage of development, a wide range of carbon-based building blocks and network forming chemistry afforded a large library of aPOPs with rich structures and properties. Recently, implanting main group elements with diverse geometric structures and electronic configurations into aPOPs has proven to be a useful tool to fine-tune the structures and properties of these polymers. Herein, we outline the recent advances in the field of main group (MG)-aPOPs where main-group elements either played unique roles in tuning the structures and properties of MG-aPOPs, or offered new strategies in the synthesis of MG-aPOPs. Furthermore, this Review discusses various challenges remaining in the field from the perspectives of synthetic strategies and characterization techniques, and presents some specific studies that may potentially address the challenges.

Hydrogenation of levulinic acid to γ-valerolactone over hydrophobic Ru@HCP catalysts

This study introduces an efficient strategy for promoting the synthesis of γ-valerolactone (GVL) via levulinic acid (LA) hydrogenation. A series of hyper-crosslinked porous polymer (HCP) supported Ru catalysts with different monomers were prepared. The wettabilities were controlled by the surface functional groups. The hydrophobic catalysts showed much higher activity than the hydrophilic ones in the hydrogenation of LA to GVL, highly possible due to the substrate enrichment. Further insight showed that the reaction proceeded through the 4-HVA route. These results illustrated the importance of surface wettability in bio-based molecule upgrading, which is beneficial for catalyst design.

Organic porous heterogeneous composite with antagonistic catalytic sites as a cascade catalyst for continuous flow reaction

One-pot cascade catalytic reactions easily allow the circumvention of pitfalls of traditional catalytic reactions, such as multi-step syntheses, longer duration, waste generation, and high operational cost. Despite advances in this area, the facile assimilation of chemically antagonistic bifunctional sites in close proximity inside a well-defined scaffold via a process of rational structural design still remains a challenge. Herein, we report the successful fusion of incompatible acid-base active sites in an ionic porous organic polymer (iPOP), 120-MI@OH, via a simple ion-exchange strategy. The fabricated polymer catalyst, 120-MI@OH, performed exceedingly well as a cascade acid-base catalyst in a deacetylation-Knoevenagel condensation reaction under mild and eco-friendly continuous flow conditions. In addition, the abundance of spatially isolated distinct acidic (imidazolium cations) and basic (hydroxide anions) catalytic sites give 120-MI@OH its excellent solid acid and base catalytic properties. To demonstrate the practical relevance of 120-MI@OH, stable millimeter-sized spherical composite polymer bead microstructures were synthesized and utilized in one-pot cascade catalysis under continuous flow, thus illustrating promising catalytic activity. Additionally, the heterogeneous polymer catalyst displayed good recyclability, scalability, as well as ease of fabrication. The superior catalytic activity of 120-MI@OH can be rationalized by its unique structure that reconciles close proximity of antagonistic catalytic sites that are sufficiently isolated in space.

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.