Heavy-Metal Ions Removal and Iodine Capture by Terpyridine Covalent Organic Frameworks

Porous materials are excellent candidates for water remediation in environmental issues. However, it is still a key challenge to design efficient adsorbents for rapid water purification from various heavy metal ions-contaminated wastewater in one step. Here, two robust nitrogen-rich covalent organic frameworks (COFs) bearing terpyridine units on the pore walls by a "bottom-up" strategy are reported. Benefitting from the strong chelation interaction between the terpyridine units and various heavy metal ions, these two terpyridine COFs show excellent removal efficiency and capability for Pb2+, Hg2+, Cu2+, Ag+, Cd2+, Ni2+, and Cr3+ from water. These COFs are shown to remove such heavy metal ions with >90% of contents at one time after the aqueous metal ions mixture is passed through the COF filter. The nitrogen-rich features of the COFs also endow them with the capability of capturing iodine vapors, offering the terpyridine COFs the potential for environmental remediation applications.

High-Performance Porous Organic Polymers for Environmental Remediation of Toxic Gases

Sulfur dioxide (SO2) is a harmful acidic gas generated from power plants and fossil fuel combustion and represents a significant health risk and threat to the environment. Benzimidazole-linked polymers (BILPs) have emerged as a promising class of porous solid adsorbents for toxic gases because of their chemical and thermal stability as well as the chemical nature of the imidazole moiety. The performance of BILPs in SO2 capture was examined by synergistic experimental and theoretical studies. BILPs exhibit a significantly high SO2 uptake of up to 8.5 mmol g-1 at 298 K and 1.0 bar. The density functional theory (DFT) calculations predict that this high SO2 uptake is due to the dipole-dipole interactions between SO2 and the functionalized polymer frames through O2S(δ+)···N(δ-)-imine and O═S═O(δ-)···H(δ+)-aryl and intermolecular attraction between SO2 molecules (O═S═O(δ-)···S(δ+)O2). Moderate isosteric heats of adsorption (Qst ≈ 38 kJ mol-1) obtained from experimental SO2 uptake studies are well supported by the DFT calculations (≈40 kJ mol-1), which suggests physisorption processes enabling rapid adsorbent regeneration for reuse. Repeated adsorption experiments with almost identical SO2 uptake confirm the easy regeneration and robustness of BILPs. Moreover, BILPs possess very high SO2 adsorption selectivity at low concentration over carbon dioxide (CO2), methane (CH4), and nitrogen (N2): SO2/CO2, 19-24; SO2/CH4, 118-113; SO2/N2, 600-674. This study highlights the potential of BILPs in the desulfurization of flue gas or other gas mixtures through capturing trace levels of SO2.

Sub-micro porous thin polymer membranes for discriminating H2 and CO2

Polymeric membranes with high permeance and remarkable selectivity for simultaneous H2 purification and CO2 capture under industry-relevant conditions are absent. Herein, sub-micro pores with precise molecular sieving capability are created in ultra-thin (13-30 nm) polymer membranes via controllable transformation of amine-linked polymer (ALP) films into benzimidazole-and-amine-linked polymer (BIALP) layers. The BIALP membranes exhibit stable unprecedented H2/CO2 selectivity of 120 with a H2 permeance of 315 GPU. Furthermore, high pressure (up to 11 bar) and thermal (up to 300 °C) resistance is delivered. This work provides a concept on designing porous polymeric membranes for precise molecular discrimination.

Selective Metal-Free CO2 Photoreduction in Water Using Porous Nanostructures with Internal Molecular Free Volume

The conversion of CO2 to a sole carbonaceous product using photocatalysis is a sustainable solution for alleviating the increasing levels of CO2 emissions and reducing our dependence on nonrenewable resources such as fossil fuels. However, developing a photoactive, metal-free catalyst that is highly selective and efficient in the CO2 reduction reaction (CO2RR) without the need for sacrificial agents, cocatalysts, and photosensitizers is challenging. Furthermore, due to the poor solubility of CO2 in water and the kinetically and thermodynamically favored hydrogen evolution reaction (HER), designing a highly selective photocatalyst is challenging. Here, we propose a molecular engineering approach to design a photoactive polymer with high CO2 permeability and low water diffusivity, promoting the mass transfer of CO2 while suppressing HER. We have incorporated a contorted triptycene scaffold with "internal molecular free volume (IMFV)" to enhance gas permeability to the active site by creating molecular channels through the inefficient packing of polymer chains. Additionally, we introduced a pyrene moiety to promote visible-light harvesting capability and charge separation. By leveraging these qualities, the polymer exhibited a high CO generation rate of 77.8 μmol g-1 h-1, with a high selectivity of ∼98% and good recyclability. The importance of IMFV was highlighted by replacing the contorted triptycene unit with a planar scaffold, which led to a selectivity reversal favoring HER over CO2RR in water. In situ electron paramagnetic resonance (EPR), time-resolved photoluminescence spectroscopy (TRPL), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques, further supported by theoretical calculations, were employed to enlighten the mechanistic insight for metal-free CO2 reduction to exclusively CO in water.

Highly stable Ru-complex-based metal-covalent organic frameworks as novel type of electrochemiluminescence emitters for ultrasensitive biosensing

Developing novel types of high-performance electrochemiluminescence (ECL) emitters is of great significance for constructing ultrasensitive ECL sensors. Herein, a highly stable metal-covalent organic framework (MCOF), termed Ru-MCOF, has been devised and synthesized by employing a classic ECL luminophore, tris(4,4'-dicarboxylicacid-2,2'-bipyridyl)ruthenium(II) (Ru(dcbpy)₃²⁺), as building unit and applied as a novel ECL probe to construct an ultrasensitive ECL sensor for the first time. Impressively, the topologically ordered and porous architectures of the Ru-MCOF not only allow Ru(bpy)₃²⁺ units to precisely locate and homogeneously distribute in the skeleton via strong covalent bonds but also facilitate the transport of co-reactants and electrons/ions in channels to promote the electrochemical activation of both external and internal Ru(bpy)₃²⁺ units. All these features endow the Ru-MCOF with excellent ECL emission, high ECL efficiency, and outstanding chemical stability. As expected, the constructed ECL biosensor based on the Ru-MCOF as a high-efficiency ECL probe accomplishes the ultrasensitive detection of microRNA-155. Overall, the synthesized Ru-MCOF not only enriches the MCOF family but also displays excellent ECL performance and thus expands the application of MCOFs in bioassays. Considering the structural diversity and tailorability of MCOFs, this work opens a new horizon to design and synthesize high-performance ECL emitters, therefore paving a new way to develop highly stable and ultrasensitive ECL sensors and motivating further research on MCOFs.

A Novel 3D-Morphology Pyrene-Derived Conjugated Fluorescence Polymer for Picric Acid Detection

Aggregation-induced quenching (ACQ) is a hard problem in fluorescence material, leading to a poor utilization rate of fluorophores. In this work, 1,3,6,8-tetrakis(4-formylphenyl)pyrene (TFPPy) was synthesized and used as a precursor to build two kinds of fluorescence polymer. The TFFPy molecule with D2h symmetry can easily form polymers with C3 symmetry amines through the Schiff base reaction, making the resulting polymer a 3D amorphous material. Thus, ACQ of fluorophore can be reduced to minimum, making the most usage of the fluorescence of pyrene core. Fluorescence titration and DFT calculation can clearly prove this conclusion. The resulting CPs showed a highly sensitivity to picric acid, down to 3.43 ppm in solution, implying its potential in explosive detection.

Macroscale Conjugated Microporous Polymers: Controlling Versatile Functionalities Over Several Dimensions

Since discovered in 2007, conjugated microporous polymers (CMPs) have been developed for numerous applications including gas adsorption, sensing, organic and photoredox catalysis, energy storage, etc. While featuring abundant micropores, the structural rigidity derived from CMPs' stable π-conjugated skeleton leads to insolubility and thus poor processability, which severely limits their applicability, e.g., in CMP-based devices. Hence, the development of CMPs whose structure can not only be controlled on the micro- but also on the macroscale have attracted tremendous interest. In conventional synthesis procedures, CMPs are obtained as powders, but in recent years various bottom-up synthesis strategies have been developed, which yield CMPs as thin films on substrates or as hybrid materials, allowing to span length scales from individual conjugated monomers to micro-/macrostructures. This review surveys recent advances on the construction of CMPs into macroscale structures, including membranes, films, aerogels, sponges, and other architectures. The focus is to describe the underlying fabrication techniques and the implications which follow from the macroscale morphologies, involving new chemistry and physics in such materials for applications like molecular separation/filtration/adsorption, energy storage and conversion, photothermal transformation, sensing, or catalysis.

Triazine-based porous organic polymers for reversible capture of iodine and utilization in antibacterial application

The capture and safe storage of radioactive iodine (¹²⁹I or ¹³¹I) are of a compelling significance in the generation of nuclear energy and waste storage. Because of their physiochemical properties, Porous Organic Polymers (POPs) are considered to be one of the most sought classes of materials for iodine capture and storage. Herein, we report on the preparation and characterization of two triazine-based, nitrogen-rich, porous organic polymers, NRPOP-1 (SA_BET = 519 m² g⁻¹) and NRPOP-2 (SA_BET = 456 m² g⁻¹), by reacting 1,3,5-triazine-2,4,6-triamine or 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene with thieno[2,3-b]thiophene-2,5-dicarboxaldehyde, respectively, and their use in the capture of volatile iodine. NRPOP-1 and NRPOP-2 showed a high adsorption capacity of iodine vapor with an uptake of up to 317 wt % at 80 °C and 1 bar and adequate recyclability. The NRPOPs were also capable of removing up to 87% of iodine from 300 mg L⁻¹ iodine-cyclohexane solution. Furthermore, the iodine-loaded polymers, I₂@NRPOP-1 and I₂@NRPOP-2, displayed good antibacterial activity against Micrococcus luteus (ML), Escherichia coli (EC), and Pseudomonas aeruginosa (PSA). The synergic functionality of these novel polymers makes them promising materials to the environment and public health.

High-Strength, Microporous, Two-Dimensional Polymer Thin Films with Rigid Benzoxazole Linkage

Two-dimensional (2D) rigid polymers provide an opportunity to translate the high-strength, high-modulus mechanical performance of classic rigid-rod 1D polymers across a plane by extending covalent bonding into two dimensions while simultaneously reducing density due to microporosity by structural design. Thus far, this potential has remained elusive because of the challenge of producing high-quality 2D polymer thin films, particularly those with irreversible, rigid benzazole linkages. Here, we present a facile two-step process that allows the deposition of a uniform intermediate film network via reversible, non-covalent interactions, followed by a subsequent solid-state annealing step that facilitates the irreversible conversion to a 2D covalently bonded polymer product with benzoxazole linkages. We demonstrate the versatility of this synthesis method by producing films with four different aromatic core units. The resulting films show microporosity and anisotropy with a 2D layered structure that can be exfoliated into few-layer nanosheets using a freeze-thaw method. These films have promising mechanical properties with an in-plane ultimate tensile strength of nearly 40 MPa and axial tensile and transverse compressive elastic moduli on the scale of several GPa, rivaling the performance of solution-cast films of 1D polybenzoxazole, as well as several other 1D high-strength polymer films.

Dimensionally Stable Polyimide Frameworks Enabling Long-Life Electrochemical Alkali-Ion Storage

Organic electrode materials hold unique advantages for electrochemical alkali-ion storage but cannot yet fulfill their potential. The key lies in the design of structurally stable candidates that have negligible solution solubility and can withstand thousands of cycles under operation. To this end, we demonstrate here the preparation of dimensionally stable polyimide frameworks from the two-dimensional cross-linking of tetraaminobenzene and dianhydride. The product consists of hierarchically assembled nanosheets with thin thickness and abundant porosity. Its robust molecular frameworks and advantageous nanoscale features render our polymeric material a promising cathode candidate for both sodium-ion and potassium-ion batteries. Most strikingly, an extraordinary cycle life of up to 6000 cycles at 2 A g^-1 is demonstrated, outperforming most of its competitors. Theoretical simulations support the great activity of our polymeric product for the electrochemical alkali-ion storage.

Porous Organic Polymers for Catalytic Conversion of Carbon Dioxide

To overcome the challenges of global warming and environmental pollution, it is necessary to reduce the concentration of carbon dioxide (CO₂ ) in the atmosphere, which is mainly accumulated in the air through the burning of fossil fuels. Therefore, the development of environmentally friendly strategies to capture carbon dioxide and convert it into value-added products offers a promising way forward for reducing carbon dioxide concentration in the atmosphere. In this context, POPs (porous organic polymers) have shown great potential as CO₂ selective adsorbents due to their high specific surface area, chemical stability, nanoscale porosity and structural diversity, as well as POPs based heterogeneous catalysts for CO₂ conversion. This review provides a concise account of preparation methods of various POPs, challenges and current development trends of POPs in photocatalytic CO₂ reduction, electrocatalytic CO₂ reduction and chemical CO₂ conversion.

A Comparative Study of Redox-Active Dithiafulvenyl-Functionalized 1,3,6,8-Tetraphenylpyrene Derivatives

A series of 1,3,6,8-tetraphenylpyrene (TPPy) derivatives substituted with redox-active 1,4-dithiafulvenyl (DTF) groups was synthesized and characterized. The conformational properties of these DTF-TPPys and their TPPy precursors were assessed by X-ray single-crystal and nuclear magnetic resonance analyses. Their electronic and redox properties were examined by ultraviolet-visible absorption, fluorescence, and cyclic voltammetric analyses. The DTF substitution was found to strongly modify the absorption, emission, and electrochemical properties, while detailed effects can be linked to substitution patterns and alkyl side chains attached to the DTF groups. Furthermore, the DTF-TPPy derivatives showed sensitivity to acids; in particular, the vinylic proton of DTF group could undergo efficient proton/deuterium exchange with D₂O in an acidic medium.

Facile fabrication of hollow tubular covalent organic frameworks using decomposable monomer as building block

In this study, a commercial and low-toxicity hydrazide-containing building block has been used to construct azine-linked covalent organic frameworks (COFs). New style COFs were constructed between flexible formic hydrazide (FH) and 1,3,5-triformylphloroglucinal (Tp) or 1,3,5-triformylbenzene (TFB). The two resulting COFs (TpFH and TFBFH) exhibited uniform hollow tubular morphology (20–50 nm for TpFH, 50–100 nm for TFBFH). Compared to hydrazine, FH has low-toxicity and is a flexible monomer, consisting of amine and aldehyde groups. The decomposition of FH slows down the reaction rate and the as-synthesized FH-series COFs (708 m² g⁻¹ for TpFH and 888 m² g⁻¹ for TFBFH) had higher specific surface area than hydrazine-series COFs (617 m² g⁻¹ for TpAzine and 472 m² g⁻¹ for TFBAzine). A detailed time-dependent investigation was carried out to interpret the mechanism of hollow structure formation, and Ostwald ripening possibly happens during the formation of hollow COF microstructures. Considering the porous and high density N, O elements of these materials, preliminary applications of the metal ions removal from aqueous solution and gas storage were implemented.

In this study, an efficient and green strategy has been used to synthesize chemically stable COFs with a hollow microtubular structure using decomposition aldehyde-containing monomer, and high affinities toward metal ions or gas molecules.

Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m2 g−1 for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI).

Synthesis methods of microporous organic polymeric adsorbents: a review

MOPs can be synthesized in a large variety of ways, which affect their pores and surface area. Variation in synthesis and porosity has a significant effect on their adsorption properties.

Fluorescent aminal linked porous organic polymer for reversible iodine capture and sensing

A novel triazene-anthracene-based fluorescent aminal linked porous organic polymer (TALPOP) was prepared via metal free-Schiff base polycondensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)anthracene and 2-furaldehyde. The polymer has exceptional chemical and thermal stabilities and exhibit good porosity with Brunauer–Emmett–Teller surface area of 401 m²g⁻¹. The combination of such porosity along with the highly conjugated heteroatom-rich framework enabled the polymer to exhibit exceptional iodine vapor uptake of up to 314 wt % and reversible iodine adsorption in solution. Because of the inclusion of the anthracene moieties, the TALPOP exhibited excellent detection sensitivity towards iodine via florescence quenching with K_sv value of 2.9 × 10³ L mol⁻¹. The cost effective TALPOP along with its high uptake and sensing of iodine, make it an ideal material for environmental remediation.

Molecularly Imprinted Porous Aromatic Frameworks for Molecular Recognition

Porous aromatic frameworks (PAFs) are an important class of porous materials that are well-known for their ultralarge surface areas and superb stabilities. Basically, PAF solids are constructed from periodically arranged phenyl fragments connected via C-C bonds (generally), which provide vast accessible surfaces that can be modified with functional groups and intrinsic pathways for rapid mass transfer. Molecular imprinting technology (MIT) is an effective method for producing binding sites with a specific geometry and size that complement a template object. This review focuses on the integration of MIT into PAF structures via state-of-the-art coupling chemistry to expand the application of porous materials in the fields of metal ion extraction (including the nuclear element uranium) and selective catalysis. Additionally, a concise outlook on the rational construction of molecularly imprinted porous aromatic frameworks is discussed in terms of developing next-generation porous materials for broader applications.

Porous Aromatic Frameworks (PAFs)

Porous aromatic frameworks (PAFs) represent an important category of porous solids. PAFs possess rigid frameworks and exceptionally high surface areas, and, uniquely, they are constructed from carbon-carbon-bond-linked aromatic-based building units. Various functionalities can either originate from the intrinsic chemistry of their building units or are achieved by postmodification of the aromatic motifs using established reactions. Specially, the strong carbon-carbon bonding renders PAFs stable under harsh chemical treatments. Therefore, PAFs exhibit specificity in their chemistry and functionalities compared with conventional porous materials such as zeolites and metal organic frameworks. The unique features of PAFs render them being tolerant of severe environments and readily functionalized by harsh chemical treatments. The research field of PAFs has experienced rapid expansion over the past decade, and it is necessary to provide a comprehensive guide to the essential development of the field at this stage. Regarding research into PAFs, the synthesis, functionalization, and applications are the three most important topics. In this thematic review, the three topics are comprehensively explained and aptly exemplified to shed light on developments in the field. Current questions and a perspective outlook will be summarized.

Advances in Conjugated Microporous Polymers

Conjugated microporous polymers (CMPs) are a unique class of materials that combine extended π-conjugation with a permanently microporous skeleton. Since their discovery in 2007, CMPs have become established as an important subclass of porous materials. A wide range of synthetic building blocks and network-forming reactions offers an enormous variety of CMPs with different properties and structures. This has allowed CMPs to be developed for gas adsorption and separations, chemical adsorption and encapsulation, heterogeneous catalysis, photoredox catalysis, light emittance, sensing, energy storage, biological applications, and solar fuels production. Here we review the progress of CMP research since its beginnings and offer an outlook for where these materials might be headed in the future. We also compare the prospect for CMPs against the growing range of conjugated crystalline covalent organic frameworks (COFs).

Conjugated porous polymers: incredibly versatile materials with far-reaching applications

This review discusses conjugated porous polymers and focuses on relating design principles and synthetic methods to key properties and applications such as (photo)catalysis, gas storage, chemical sensing, energy storage and environmental remediation.

Synthesis of 1,6-disubstituted pyrene-based conjugated microporous polymers for reversible adsorption and fluorescence sensing of iodine

Four 1,6-disubstituted pyrene-based fluorescent conjugated microporous polymers were synthesized by Sonogashira–Hagihara reaction, trimerization reaction of –CN, and Friedel–Crafts reaction, respectively, which can efficient capture and sense I₂.

Ultrastable conductive microporous covalent triazine frameworks based on pyrene moieties provide high-performance CO2 uptake and supercapacitance

Two pyrene-functionalized CTFs through ionothermal treatment TCNPy in the presence of molten zinc chloride at 500 °C, which displayed high-performance CO₂ uptake and supercapacitance.

Electrospun carbon nanofibers with multi-aperture/opening porous hierarchical structure for efficient CO2 adsorption

HYPOTHESIS

Carbonaceous materials are believed to be excellent source for developing essential vessels for carbon dioxide (CO₂) adsorption. However, most of the carbonaceous materials used for CO₂ capture have particle form, which is hard to recycle and also may cause choking of the gas pipes. Additionally, they also either require chemical activation or attachment of any functional groups for proficient CO₂ capture. Thus, facile fabrication of multi-aperture porous carbon nanofiber (CNF) based CO₂ sorbent via combination of three simple steps of electrospinning, washing, and carbonization, may be an effective approach for developing efficient sorbents for CO₂ capture.

EXPERIMENT

PAN/PVP composite solution was electrospun, PVP was used as pore forming template and PAN was opted as nitrogen rich precursor for carbon during electrospinning process. Selective removal of PVP from the electrospun PAN/PVP fiber matrix prior to carbonization generated highly rough and extremely porous PAN nanofibers, which were then carbonized to develop multi-aperture/opening porous carbon nanofibers (PCNF) with ultra-small pores with average pore diameter of ~0.71 nm.

FINDINGS

Synthesized PCNF exhibited high CO₂ gas selectivity (S = 20) and offered superior CO₂ adsorption performance of 3.11 mmol/g. Moreover, no apparent change in mass for up to 50 cycles of CO₂ adsorption/desorption unveil the long-term stability of synthesized PCNF, making them a potential candidate for CO₂ adsorption application.

Imidazole-Linked Crystalline Two-Dimensional Polymer with Ultrahigh Proton-Conductivity

Proton-exchange membrane fuel cells are promising energy devices for a sustainable future due to green features, high power density, and mild operating conditions. A facile proton-conducting membrane plays a pivotal role to boost the efficiency of fuel cells, and hence focused research in this area is highly desirable. Major issues associated with the successful example of Nafion resulted in the search for alternate proton conducting materials. Even though proton carrier loaded crystalline porous organic frameworks have been used for proton-conduction, the weak host-guest interactions limited their practical use. Herein, we developed a crystalline 2D-polymer composed of benzimidazole units as the integral part, prepared by the condensation of aryl acid and diamine in polyphosphoric acid medium. The imidazole linked-2D-polymer exhibits ultrahigh proton conductivity (3.2 × 10^-2 S cm^-1) (at 95% relative humidity and 95 °C) in the pristine state, which is highest among the undoped porous organic frameworks so far reported. The present strategy of a crystalline proton-conducting 2D-polymer will lead to the development of new high performing crystalline solid proton conductor.

Double-Helical Ag-S Rod-Based Porous Coordination Polymers with Double Activation: σ-Active and π-Active Functions

As common coinage metals, silver and silver compounds have very rich application in the organic catalytic reaction. Immobilization of silver compounds on heterogeneous media is the most common way used in industrial catalytic reactions. In this work, we designed and synthesized a new heterogeneous porous silver catalyst, with in situ-formed Ag-S rods as connecting nodes and thiosemicarbazide-functionalized linear ligands, used in both σ- and π-catalytic transformations. Strong Ag-S bonds bypassed the loss of noble silver elements and inhibited the formation of nonporous silver particles which always led to the decrease of yields in homogenous reactions. Furthermore, various derivatives of propargylamines and phenylacetylenes were applied as both σ and π-active substrates with moderate to good yields.

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.

Pyrene Bearing Azo-Functionalized Porous Nanofibers for CO2 Separation and Toxic Metal Cation Sensing

A novel luminescent azo-linked polymer (ALP) has been constructed from 1,3,6,8-tetra(4-aminophenyl)pyrene using a copper(I)-catalyzed oxidative homocoupling reaction. The polymer displays high porosity with a Brunauer-Emmett-Teller surface area of 1259 m² g^-1 and narrow pore size distribution (1.06 nm) and is able to take up a significant amount of CO₂ (2.89 mmol g^-1) at 298 K and 1.00 bar with a high isosteric heat of adsorption of 27.5 kJ mol^-1. Selectivity studies applying the ideal adsorbed solution theory revealed that the novel polymer has moderately good selectivities for CO₂/N₂ (55.1) and CO₂/CH₄ (10.9). Furthermore, the ALP shows fluorescence quenching in the presence of Hg²⁺, Pb²⁺, Tl⁺, and Al³⁺ ions. Compared with these ions, the ALP showed no sensitivity to light metal ions such as Na⁺, K⁺, and Ca²⁺ in ethanol-water solution, clearly indicating the high selectivity of the ALP toward heavy metal ions. The exceptional physiochemical stability, high porosity, and strong luminescence make this polymer an excellent candidate as a fluorescent chemical sensor for the detection of heavy metal ions.

Facile manufacture of porous organic framework membranes for precombustion CO2 capture

The development of new membranes with high H₂ separation performance under industrially relevant conditions (high temperatures and pressures) is of primary importance. For instance, these membranes may facilitate the implementation of energy-efficient precombustion CO₂ capture or reduce energy intensity in other industrial processes such as ammonia synthesis. We report a facile synthetic protocol based on interfacial polymerization for the fabrication of supported benzimidazole-linked polymer membranes that display an unprecedented H₂/CO₂ selectivity (up to 40) at 423 K together with high-pressure resistance and long-term stability (>800 hours in the presence of water vapor).

Exploration of Thiazolo[5,4-d]thiazole Linkages in Conjugated Porous Organic Polymers for Chemoselective Molecular Sieving

Porous organic polymers (POPs) have attracted significant attention towards molecular adsorption in recent years due to their high porosity, diverse functionality and excellent chemical stability. In this work, we present a systematic case study on the formation of thiazolo[5,4-d]thiazole (TzTz) linkages through model compounds and its integration to synthesize a set of three novel, thermo-chemically stable TzTz-linked POPs, namely TzTz-POP-3, TzTz-POP-4, and TzTz-POP-5 with triphenylbenzene, tetraphenylpyrene and tetra(hydroxyphenyl)methane cores, respectively. Interestingly, the integrated TzTz moiety of the represented TzTz-POP-3 renders chemoselective removal of organic dye fluorescein (FL) from a mixture with parafuchsine (FU) in aqueous solution. The TzTz-POP-3 offered excellent chemoselectivity of ≈1:7 (FL:FU), compared to alike porous materials demonstrated for similar applications due to the presence of multiple active anchoring sites coupled with permanent porosity and appropriate pore window.

Concentration-Directed Polymorphic Surface Covalent Organic Frameworks: Rhombus, Parallelogram, and Kagome

Polymorphic single-layered covalent organic frameworks (sCOFs) via on-surface synthesis have been investigated by employing the tetradentate monomer 1,3,6,8-tetrakis(p-formylphenyl)pyrene with D_2h symmetry and ditopic linear diamine building blocks. Three kinds of well-ordered sCOFs, including rhombus, parallelogram, and Kagome networks, are observed on the graphite surface by scanning tunnel microscopy. The pore size and periodicity of sCOFs are tunable by employing diamine monomers with different lengths. Statistical analysis reveals that two types of quadrate networks are preferred at high concentration, whereas the occupancy of Kagome networks increases at low concentration. This trend can be understood by the differences in the network density of three kinds of networks. The reversibility and the self-sorting ability of the dynamic covalent reaction make it possible to control the polymorphic distribution similar to the principle demonstrated in supramolecular self-assembly.

Porous Organic Polymers for Post-Combustion Carbon Capture

One of the most pressing environmental concerns of our age is the escalating level of atmospheric CO₂ . Intensive efforts have been made to investigate advanced porous materials, especially porous organic polymers (POPs), as one type of the most promising candidates for carbon capture due to their extremely high porosity, structural diversity, and physicochemical stability. This review provides a critical and in-depth analysis of recent POP research as it pertains to carbon capture. The definitions and terminologies commonly used to evaluate the performance of POPs for carbon capture, including CO₂ capacity, enthalpy, selectivity, and regeneration strategies, are summarized. A detailed correlation study between the structural and chemical features of POPs and their adsorption capacities is discussed, mainly focusing on the physical interactions and chemical reactions. Finally, a concise outlook for utilizing POPs for carbon capture is discussed, noting areas in which further work is needed to develop the next-generation POPs for practical applications.

Pyrene-cored covalent organic polymers by thiophene-based isomers, their gas adsorption, and photophysical properties

Two new pyrene‐cored covalent organic polymers (COPs), CK‐COP‐1 and CK‐COP‐2, were synthesized via the one‐step polymerization of two thiophene‐based isomers, 1,3,6,8‐tetra(thiophene‐2‐yl) pyrene (L₁) and 1,3,6,8‐tetra(thiophene‐3‐yl) pyrene (L₂). The resulting pyrene‐cored COPs exhibit rather different surface areas of 54 m² g⁻¹ and 615 m²g⁻¹ for CK‐COP‐1 and CK‐COP‐2, respectively. The CO₂ uptake capacities of CK‐COP‐1 and CK‐COP‐2 also show different values of 2.85 and 9.73 wt % at 273 K, respectively. Furthermore, CK‐COP‐2 offers not only a larger CO₂ adsorption capacity but also a better CO₂/CH₄ selectivity at 273 K compared with CK‐COP‐1. CK‐COP‐1 and CK‐COP‐2 also exhibit considerable differences in their photophysical property. The different structure and properties of CK‐COPs could be attributed to the isomer effect of their corresponding thiophene‐based monomers. © 2017 Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2383–2389