A New Strategy to Microporous Polymers: Knitting Rigid Aromatic Building Blocks by External Cross-Linker

Highly Porous Organic Polymers for Hydrogen Fuel Storage

Hydrogen (H2) is one of the best candidates to replace current petroleum energy resources due to its rich abundance and clean combustion. However, the storage of H2 presents a major challenge. There are two methods for storing H2 fuel, chemical and physical, both of which have some advantages and disadvantages. In physical storage, highly porous organic polymers are of particular interest, since they are low cost, easy to scale up, metal-free, and environmentally friendly. In this review, highly porous polymers for H2 fuel storage are examined from five perspectives: (a) brief comparison of H2 storage in highly porous polymers and other storage media; (b) theoretical considerations of the physical storage of H2 molecules in porous polymers; (c) H2 storage in different classes of highly porous organic polymers; (d) characterization of microporosity in these polymers; and (e) future developments for highly porous organic polymers for H2 fuel storage. These topics will provide an introductory overview of highly porous organic polymers in H2 fuel storage.

Solvent-Induced Self-Assembly Strategy to Synthesize Well-Defined Hierarchically Porous Polymers

Porous polymers with well-orchestrated nanomorphologies are useful in many fields, but high surface area, hierarchical structure, and ordered pores are difficult to be satisfied in one polymer simultaneously. Herein, a solvent-induced self-assembly strategy to synthesize hierarchical porous polymers with tunable morphology, mesoporous structure, and microporous pore wall is reported. The poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer micelles are cross-linked via Friedel-Crafts reaction, which is a new way to anchor micelles into porous polymers with well-defined structure. Varying the polarity of the solvent has a dramatic effect upon the oleophobic/oleophylic interaction, and the self-assembly structure of PEO-b-PS can be tailored from aggregated nanoparticles to hollow spheres even mesoporous bulk. A morphological phase diagram is accomplished to systematically evaluate the influence of the composition of PEO-b-PS and the mixed solvent component on the pore structure and morphology of products. The hypercrosslinked hollow polymer spheres provide a confined microenvironment for the in situ reduction of K₂ PdCl₄ to ultrasmall Pd nanoparticles, which exhibit excellent catalytic performance in solvent-free catalytic oxidation of hydrocarbons and alcohols.

Highly Porous Hypercrosslinked Polymers Derived from Biobased Molecules

Highly porous and hyper-cross-linked polymers (HCPs) have a range of applications and are typically synthesized in an unsustainable manner. Herein, HCPs were synthesized from abundant biobased or biorelated compounds in sulfolane with iron(III) chloride as Lewis acid catalyst. As reactants, quercetin, tannic acid, phenol, 1,4-dimethoxybenzene, glucose, and a commercial bark extract were used. The HCPs had high CO₂ uptake (up to 3.94 mmol g^-1 at 0 °C and 1 bar), total pore volumes (up to 1.86 cm³  g^-1 ), and specific surface areas (up to 1440 m²  g^-1 ). ¹ H NMR, ¹³ C NMR, and IR spectroscopy, wide-angle X-ray scattering, elemental analysis, and SEM revealed, for example, that the HCPs consisted of amorphous and cross-linked aromatic and phenolic structures with significant contents of aliphatics, oxygen, and sulfur.

In Situ Cross-Linked Gel Polymer Electrolyte Membranes with Excellent Thermal Stability for Lithium Ion Batteries

Novel gel polymer electrolyte membranes with excellent thermal stability are fabricated via a combination of physical blending and chemical cross-linking procedures. Precursor porous membranes made of poly(vinylidene fluoride) (PVDF) and polystyrene-poly(ethylene oxide)-polystyrene (PS-PEO-PS) triblock copolymer composites are prepared by a phase-inversion technique, and the gel polymer electrolyte membranes are finished by in situ hypercrosslinking of the PS segments in precursor membranes. The latter cross-linking procedure could consolidate pore configuration and thus greatly enhance the thermal stability of the obtained cross-linked composite membranes. The membranes with optimal PS/PEO ratios can retain reasonable porosity with little dimensional shrinkage at high temperatures up to 260 °C. Gel polymer electrolytes with these cross-linked membranes as matrices exhibit much higher ionic conductivities (up to 1.38 × 10^-3 S cm^-1 at room temperature) than those based on pure PVDF membranes. Li/LiFePO₄ half cells assembled with these gel polymer electrolytes exhibit good cycling performance and rate capability. These results indicate that the Friedel-Crafts reaction based hypercrosslinking is an efficient method to construct highly heat-resistant polymer electrolytes for lithium ion batteries, particularly advantageous in applications that require high-temperature usage.

Amino-functionalized hypercrosslinked polymers for highly selective anionic dye removal and CO2/N2 separation

Recently, great improvements have been achieved in the fabrication of adsorbents.

Effects of synthesis methodology on microporous organic hyper-cross-linked polymers with respect to structural porosity, gas uptake performance and fluorescence properties

The structural characteristics of hyper-cross-linked polymers (HCPs) make them interesting for a wide variety of applications.

A step forward in solvent knitting strategies: ruthenium and gold phosphine complex polymerization results in effective heterogenized catalysts

A knitting strategy has been applied to obtain metal–phosphine porous organic polymers (Kphos(M)), resulting in effective heterogenized catalysts for different reactions.

Continuous flow knitting of a triptycene hypercrosslinked polymer

Hypercrosslinked polymers suitable for carbon capture were produced in continuous flow synthesis using 10% of the time required for typical batch reactions, precluding the need for lengthy reactions to produce microporous polymeric adsorbents.

Fabrication and adsorption performance for CO2 capture of advanced nanoporous microspheres enriched with amino acids

Advanced porous organic materials with high gas storage capacity and high selectivity have been rapidly developed for CO₂ adsorbents in the recent decade, due to extremely high surface area and nanoscale pore size. Here, novel amino acids-incorporated solid adsorbents based on porous hypercrosslinked polymers were fabricated by a dispersion polymerization of an aromatic monomer and quaternary ammonium salt comonomer, subsequently a hypercrosslinked reaction and an ion-exchange step. The developed adsorbents presented mesopores structure with BET surface area up to 864 m²/g and an extremely high CO₂ capturing capacity up to 60.7 wt% (13.8 mmol/g) at 273 K/1 bar. The results also showed the adsorbent had an excellent recycling ability over repetitive adsorption-desorption cycles. All the results suggest that the amino acids-modified porous sorbents are promising CO₂ sorbents that can meet the challenges of the current CO₂ capture and storage technology.

Fast adsorption of methylene blue, basic fuchsin, and malachite green by a novel sulfonic-grafted triptycene-based porous organic polymer

In this study, a novel triptycene-based porous polymer grafted with sulfonic acid (TPP-SO3H) was successfully synthesized by the post-synthetic modification of the non-functionalized polymer TPP. The polymer TPP-SO3H was well-characterized and was found to be a fast and effective absorbent for the cationic dyes methylene blue (MEB), basic fuchsin (BF), and malachite green (MG), with over 95% removal being observed within 10 min from initial concentrations of 100 mg L-1, 100 mg L-1, and 300 mg L-1, respectively. The adsorption process for MEB, BF, and MG was pH-dependent. The adsorption behaviours for MEB, BF, and MG follow pseudo-second-order kinetics and fit the Langmuir model. Moreover, the maximum adsorption capacities of MEB, BF, and MG at room temperature were 981.8 mg g-1, 586.2 mg g-1, and 1942.5 mg g-1, respectively. It is worth noting that the values of the MEB, BF, and MG adsorption capacities on TPP-SO3H were 5.5, 3, and 1.8 times that of the non-functionalized polymer TPP based on the same adsorbent weight. It is suggested that (i) there are strong electrostatic attractions between the sulfonic groups of the TPP-SO3H and cationic dyes and (ii) the higher surface area and good porosity may contribute to the high dye adsorption capacity. Furthermore, TPP-SO3H exhibited good cyclic stability, which can be regenerated at least five times without a significant loss of adsorption capacity. Therefore, the facile strategy synthesis, as well as the excellent adsorption capacity and reusability, make polymer TPP-SO3H an attractive adsorbent for wastewater treatment.

Preparation of Microporous Organic Polymers via UV-Initiated Radical Copolymerization

UV-initiated radical copolymerization has been successfully applied for the preparation of two kinds of microporous organic polymers (MOPs) based on divinylbenzene (DVB)/bismaleimide (BMI) monomers and DVB/pentaerythritol tetraacrylate (PET4A). The obtained MOPs exhibit high BET surface areas and good CO₂ storage performance. The maximum BET surface areas of DVB/BMI and DVB/PET4A are 585 and 887 m² g^-1, respectively. Furthermore, the ester groups embedded on the DVB/PET4A copolymer skeleton can be easily converted into carboxylic groups by hydrolysis and show superior adsorption capacity of 485 mg g^-1 toward methylene blue dye. The adoption of this highly efficient polymerization strategy offers the possibility for the economical and continuous preparation of MOPs and demonstrates great potential for industrial application.

Single-Site Ruthenium Pincer Complex Knitted into Porous Organic Polymers for Dehydrogenation of Formic Acid

Owing to its capacity for reversible hydrogen storage, formic acid (FA) holds great promise as an alternative energy carrier to conventional fossil fuel systems. Whereas the decomposition of FA to hydrogen (H₂ ) and carbon dioxide (CO₂ ) through homogeneous catalysis is well established, the selective and efficient dehydrogenation of FA by a robust heterogeneous catalyst remains a challenge. A new heterogeneous ruthenium pincer framework with single-atomic sites was prepared in one step by the direct knitting of a phosphorus-nitrogen PN³ P-pincer ruthenium complex in a porous organic polymer. The heterogeneous ruthenium complex efficiently dehydrogenates formic acid in both organic and aqueous media with remarkably enhanced stability. Notably, no detectable CO was generated and a turnover number (TON) of 145 300 was attained in a continuous experiment with no significant decline in catalytic activity (in sharp contrast, a total TON of only 5600 was obtained with the homogeneous analog under the same conditions). The single-atomic sites in the porous framework combined the desirable attributes of high reactivity and selectivity of a homogeneous catalyst with the significantly enhanced catalyst stability and reusability benefits of heterogeneous catalysis.

Hyperporous-Carbon-Supported Nonprecious Metal Electrocatalysts for the Oxygen Reduction Reaction

Highly porous carbonaceous nonprecious metal catalysts for the oxygen reduction reaction are prepared by carbonization of low-cost metalloporphyrin-based hyper-crosslinked polymers (MPH-X). With high surface area (2768 m²  g^-1 ), hierarchical porous structure, and high metal loading (9.97 wt %), the obtained hyperporous carbon MPH-Fe/C catalyst exhibits high oxygen reduction reaction (ORR) activity with a half-wave potential (0.816 V) that is comparable to the 0.819 V of commercial Pt/C. Stability tests reveal that MPH-Fe/C also exhibits outstanding long-term durability and methanol tolerance. Our findings may offer an alternative approach to produce nonprecious metal ORR catalysts on a large scale owing to the low-cost MPH-X precursors with diverse metal types.

PDMS-coated hypercrosslinked porous organic polymers modified via double postsynthetic acidifications for ammonia capture

Double postsynthetic acidifications of a hypercrosslinked polymer afforded record high NH₃ adsorption capacity per surface area. Its PDMS coating provided an 40-fold enhancement of low-pressure NH₃ adsorption capacity and hydrophobicity.

A hypercrosslinked porous organic polymer was modified by post-oxidation and post-sulfonation to obtain a porous platform with a high density of acidic groups. Such an acidified material exhibits record high NH₃ adsorption capacity per surface area, fast adsorption rate, and recyclability at low desorption temperature. Noticeably, the coating of the polymer with PDMS represents a facile and efficient route to enable both a significant improvement of low-pressure NH₃ adsorption capacity (∼40-fold enhancement; from 0.04 to 1.41 mmol g^–1) with respect to the non-modified polymer at 500 ppm and hydrophobicity associated with the selective sorption of NH₃ over water vapor (hydrophilic for the non-coated material). This material is easy to prepare, cost-effective, and scalable to mass production.

Facile Synthesis of a Pentiptycene-Based Highly Microporous Organic Polymer for Gas Storage and Water Treatment

Rigid H-shaped pentiptycene units, with an intrinsic hierarchical structure, were employed to fabricate a highly microporous organic polymer sorbent via Friedel-Crafts reaction/polymerization. The obtained microporous polymer exhibits good thermal stability, a high Brunauer-Emmett-Teller surface area of 1604 m² g^-1, outstanding CO₂, H₂, and CH₄ storage capacities, as well as good adsorption selectivities for the separation of CO₂/N₂ and CO₂/CH₄ gas pairs. The CO₂ uptake values reached as high as 5.00 mmol g^-1 (1.0 bar and 273 K), which, along with high adsorption selectivity values (e.g., 47.1 for CO₂/N₂), make the pentiptycene-based microporous organic polymer (PMOP) a promising sorbent material for carbon capture from flue gas and natural gas purification. Moreover, the PMOP material displayed superior absorption capacities for organic solvents and dyes. For example, the maximum adsorption capacities for methylene blue and Congo red were 394 and 932 mg g^-1, respectively, promoting the potential of the PMOP as an excellent sorbent for environmental remediation and water treatment.

A Facile Approach to Prepare Multiple Heteroatom-Doped Carbon Materials from Imine-Linked Porous Organic Polymers

In this paper, we proposed a new strategy to prepare multiple heteroatom doped (N, P-doped) porous carbon materials with high surface area of ~1,535 m² g⁻¹ simply by pyrolysis of imine-linked porous organic polymers (POPs) synthesized via Schiff base condensation. The strategy is simple without any post-processing and various heteroatoms could be involved. Scanning electron microscopy, Raman spectra, Nitrogen gas adsorption-desorption, X-ray photoelectron spectroscopy have been used to characterize the morphology, the structure and the composition of the materials. The multiple heteroatom doped porous carbon materials also display high electrocatalytic performance as exampled by the application in oxygen reduction, which showed the catalyst favors 4-electron transfer during the process, along with superior stability and higher tolerance to methanol as compared to the Pt/C. These results indicate the present method is promising for the preparation of multi-heteroatom doped carbon materials in the application of electrocatalysis.

Hypercrosslinked porous polymer materials: design, synthesis, and applications

Hypercrosslinked polymers (HCPs) are a series of permanent microporous polymer materials initially reported by Davankov, and have received an increasing level of research interest. In recent years, HCPs have experienced rapid growth due to their remarkable advantages such as diverse synthetic methods, easy functionalization, high surface area, low cost reagents and mild operating conditions. Judicious selection of monomers, appropriate length crosslinkers and optimized reaction conditions yielded a well-developed polymer framework with an adjusted porous topology. Post fabrication of the as developed network facilitates the incorporation of various chemical functionalities that may lead to interesting properties and enhance the selection toward a specific application. To date, numerous HCPs have been prepared by post-crosslinking polystyrene-based precursors, one-step self-polycondensation or external crosslinking strategies. The advent of these methodologies has prompted researchers to construct well-defined porous polymer networks with customized micromorphology and functionalities. In this review, we describe not only the basic synthetic principles and strategies of HCPs, but also the advancements in the structural and morphological study as well as the frontiers of potential applications in energy and environmental fields such as gas storage, carbon capture, removal of pollutants, molecular separation, catalysis, drug delivery, sensing etc.

Synthesis of Bis(indolyl)methanes Using Hyper-Cross-Linked Polyaromatic Spheres Decorated with Bromomethyl Groups as Efficient and Recyclable Catalysts

Highly uniform and hyper-cross-linked polyphenanthrene and polypyrene microspheres were synthesized by Friedel-Crafts bromomethylation of phenanthrene (Phn) and pyrene (Py) in the presence of zinc bromide as a catalyst, followed by self-polymerization of bromomethylated Phn and Py. The resultant 3-D carbon microspheres consisting of micro-, meso-, and macropores bear peripheral unreacted bromomethyl groups, which are directly utilized as catalysts to efficiently promote the electrophilic substitution reaction of indoles with aldehydes to yield a variety of bis(indolyl)methanes. The important features of this catalysis are easy catalyst synthesis, high product yields, environmental benignity, short reaction time, broad substrate scope, use of nontoxic solvents, and recyclability.

One-pot synthesis of a highly porous anionic hypercrosslinked polymer for ultrafast adsorption of organic pollutants

Ultrafast adsorption of organic pollutants in water was achieved with a highly porous anionic hypercrosslinked polymer as an adsorbent.

Adsorptive removal of p-nitrophenol from water with mechano-synthesized porous organic polymers

An environmentally friendly synthesis of porous organic polymers for removing organic pollutants from water.

Efficient alkaloid capture from water using a charged porous organic polymer

Berberine hydrochloride (BH), an important alkaloid, can be captured from water and released in organic solution circularly by a charged porous polymer (TPB–HCP), which is hypercross-linked using the cost-effective Friedel–Crafts reaction using sodium tetraphenylborate as the monomer. With high BET surface area, hierarchical porous structure and charged characteristics, TPB–HCP displays excellent adsorption capacity for BH owing to the synergistic effects of size matching and electrostatic interaction.

A charged porous polymer displays excellent adsorption capacity for berberine hydrochloride from the synergistic effects of size matching and electrostatic interaction.

Facile preparation of porous organic copolymer based on triptycene and crown ether for efficient organic dye adsorption

The novel copolymer POP-TCE-15 displayed extraordinary capacity to adsorb organic dye from water.

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

Achiral polymeric supports can have important positive effects on the activity, stability and selectivity of supported chiral catalysts.

A nanoscale porous glucose-based polymer for gas adsorption and drug delivery

A glucose-based nanoporous organic polymer with the –OH group shows significant CO₂ uptake capacities and good drug release behaviour.

Knitting polycyclic aromatic hydrocarbon-based microporous organic polymers for efficient CO2 capture

In order to achieve efficient CO₂ capture, four novel microporous organic polymers, based on distinct polycyclic aromatic hydrocarbons such as fluoranthene, binaphthalene, naphthalene and phenanthrene, were successfully prepared by the solvent knitting method. N₂ sorption isotherms indicate that these polymers are predominately microporous with ultrahigh BET surface area i.e., 1788 m² g⁻¹ for fluoranthene-based Polymer 1, 1702 m² g⁻¹ for binaphthalene-based Polymer 2 and objective CO₂ uptake capacity of 24.79 wt% and 20.19 wt% (273.15 K/1.00 bar) respectively. While compared with the former two polymers, though 1227 m² g⁻¹ and 978 m² g⁻¹ are moderate in surface area, however the naphthalene-based Polymer 3 and phenanthrene-based Polymer 4 still exhibit CO₂ adsorption of up to 17.44 wt% and 18.15 wt% respectively under the similar conditions. Moreover, the H₂ storage and CH₄ adsorption in these polymers can be 2.20 wt% (77.3 K/1.13 bar) and 2.79 wt% (273.15 K/1.00 bar). More significantly, the electron-rich PAHs are proved to be new building blocks that provide a wealth of chances to produce hypercrosslinked polymers with efficient gas adsorption capacity, which are greatly influenced by the porous nature of polymers. Given the merits including mild reaction conditions, low cost, high surface area, impressive gas absorption performance, high thermal stability, these polymers are considered to be promising candidates for CO₂ capture and energy storage under more practical conditions.

In order to achieve efficient CO₂ capture, four novel microporous organic polymers, based on distinct polycyclic aromatic hydrocarbons, were successfully prepared by the solvent knitting method.

Microporous Hyper-Crosslinked Polystyrenes and Nanocomposites with High Adsorption Properties: A Review

Hyper-crosslinked (HCL) polystyrenes show outstanding properties, such as high specific surface area and adsorption capability. Several researches have been recently focused on tailoring their performance for specific applications, such as gas adsorption and separation, energy storage, air and water purification processes, and catalysis. In this review, main strategies for the realization of HCL polystyrene-based materials with advanced properties are reported, including a summary of the synthetic routes that are adopted for their realization and the chemical modification approaches that are used to impart them specific functionalities. Moreover, the most up to date results on the synthesis of HCL polystyrene-based nanocomposites that are realized by embedding these high surface area polymers with metal, metal oxide, and carbon-based nanofillers are discussed in detail, underlining the high potential applicability of these systems in different fields.

Hierarchically Porous Carbon Derived from PolyHIPE for Supercapacitor and Deionization Applications

Hierarchically porous carbon (HPC) materials with interconnected porous texture are produced from a porous poly(divinylbenzene) precursor, which is synthesized by polymerizing high-internal-phase emulsions. After carbonation, the macroporous structures of the poly(divinylbenzene) precursor are preserved and enormous micro-/mesopores via carbonation with KOH are produced, resulting in an interconnected hierarchically porous network. The prepared HPC has a maximum specific surface area of 2189 m² g^-1. The electrode materials for supercapacitors and capacitive deionization devices employing the formed HPC exhibit a high specific capacity of 88 mA h g^-1 through a voltage range of 1 V (319 F g^-1 at 1 A g^-1) and a superior electrosorption capacity of 21.3 mg g^-1 in 500 mg L^-1 NaCl solution. The excellent capacitive performance could be ascribed to the combination of high specific surface area and favorable hierarchically porous structure.