Porous covalent electron-rich organonitridic frameworks as highly selective sorbents for methane and carbon dioxide

Nitrogen-Rich Porous Polymers for Carbon Dioxide and Iodine Sequestration for Environmental Remediation

The use of fossil fuels for energy production is accompanied by carbon dioxide release into the environment causing catastrophic climate changes. Meanwhile, replacing fossil fuels with carbon-free nuclear energy has the potential to release radioactive iodine during nuclear waste processing and in case of a nuclear accident. Therefore, developing efficient adsorbents for carbon dioxide and iodine capture is of great importance. Two nitrogen-rich porous polymers (NRPPs) derived from 4-bis-(2,4-diamino-1,3,5-triazine)-benzene building block were prepared and tested for use in CO₂ and I₂ capture. Copolymerization of 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene with terephthalaldehyde and 1,3,5-tris(4-formylphenyl)benzene in dimethyl sulfoxide at 180 °C afforded highly porous NRPP-1 (SA_BET = 1579 m² g^-1) and NRPP-2 (SA_BET = 1028 m² g^-1), respectively. The combination of high nitrogen content, π-electron conjugated structure, and microporosity makes NRPPs very effective in CO₂ uptake and I₂ capture. NRPPs exhibit high CO₂ uptakes (NRPP-1, 6.1 mmol g^-1 and NRPP-2, 7.06 mmol g^-1) at 273 K and 1.0 bar. The 7.06 mmol g^-1 CO₂ uptake by NRPP-2 is the second highest value reported to date for porous organic polymers. According to vapor iodine uptake studies, the polymers display high capacity and rapid reversible uptake release for I₂ (NRPP-1, 192 wt % and NRPP-2, 222 wt %). Our studies show that the green nature (metal-free) of NRPPs and their effective capture of CO₂ and I₂ make this class of porous materials promising for environmental remediation.

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.

Cyclophosphazene-Based Hybrid Nanoporous Materials as Superior Metal-Free Adsorbents for Gas Sorption Applications

Cyclophosphazene-based inorganic-organic hybrid nanoporous materials (CHNMs) have been synthesized by a facile solvothermal method. The condensation of pyrrole with the reaction product of phosphonitrilic chloride trimer and 4-hydroxybenzaldehyde resulted in the formation of high-surface-area CHNMs. The maximum specific surface area (SA_BET) of 1328 m² g^-1 with hierarchical pore structures having micropores centered at 1.18 nm and mesopores in the range of 2.6-3.6 nm was estimated from the N₂ sorption analysis. Observation of high SA_BET could be attributed to the synergy effect exerted by the cyclophosphazene moiety owing to its three-dimensional paddle wheel structure. The metal-free adsorbent exhibited a high and reversible CO₂ uptake of 22.8 wt % at 273 K and 1 bar. The performance is on the higher side among the reported metal-free inorganic-organic hybrid nanoporous adsorbents. Moreover, the high H₂ uptake of 2.02 wt % at 77 K and 1 bar is an added advantage. The superior performance of the adsorbents for the gas sorption applications could be attributed to the combined effect of high SA_BET and hierarchical pore structure, which has made CHNMs good candidates for energy and environmental applications.

Template-free synthesis of porous carbon from triazine based polymers and their use in iodine adsorption and CO2 capture

A series of novel triazine-containing pore-tunable carbon materials (NT-POP@800-1-6), which was synthesized via pyrolysis of porous organic polymers (POPs) without any templates. NT-POP@800-1-6 possess moderate BET surface areas of 475-736 m2 g-1, have permanent porosity and plenty of nitrogen units in the skeletons as effective sorption sites, and display relatively rapid guest uptake of 56-192 wt% in iodine vapour in the first 4 h. In addition, all the samples exhibit the outstanding CO2 adsorption capacity of 2.83-3.96 mmol g-1 at 273 K and 1.05 bar. Furthermore, NT-POP@800-1-6 show good selectivity ratios of 21.2-36.9 and 3.3-7.5 for CO2/N2 or CH4/N2, respectively. We believe that our new building block design provides a general strategy for the construction of triazine-containing carbon materials from various extended building blocks, thereby greatly expanding the range of applicable molecules.

Nitrogen enriched polytriazine as a metal-free heterogeneous catalyst for the Knoevenagel reaction under mild conditions

A nitrogen-enriched nanoporous polytriazine was used as a metal-free heterogeneous organocatalyst for high-yielding ultra-fast Knoevenagel reactions under ambient conditions.

A type of thiophene-bridged silica aerogel with a high adsorption capacity for organic solvents and oil pollutants

Thiophene-bridged silica aerogel was prepared from tetraethyl orthosilicate (TEOS) and 2,5-divinyltrimethoxysilanethiophene (DVTHP) through a facile sol–gel reaction and ambient pressure drying process.

Forming a three-dimensional porous organic network via solid-state explosion of organic single crystals

Solid-state reaction of organic molecules holds a considerable advantage over liquid-phase processes in the manufacturing industry. However, the research progress in exploring this benefit is largely staggering, which leaves few liquid-phase systems to work with. Here, we show a synthetic protocol for the formation of a three-dimensional porous organic network via solid-state explosion of organic single crystals. The explosive reaction is realized by the Bergman reaction (cycloaromatization) of three enediyne groups on 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-[1,2]benzenoanthracene. The origin of the explosion is systematically studied using single-crystal X-ray diffraction and differential scanning calorimetry, along with high-speed camera and density functional theory calculations. The results suggest that the solid-state explosion is triggered by an abrupt change in lattice energy induced by release of primer molecules in the 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-[1,2]benzenoanthracene crystal lattice.

Porous organic networks are of great fundamental and technological interest. Here, the authors synthesize a three-dimensional porous organic network with high specific surface area via a solid-state explosive reaction of hexaethynyl triptycene single crystals containing primer molecules.

Controlled synthesis of conjugated polycarbazole polymers via structure tuning for gas storage and separation applications

A series of conjugated microporous polymers (CMPs) based on 1,3,6,8-tetrabromocarbazole (N4CMP-1-5) is synthesized via Suzuki cross-coupling or Sonogashira polycondensation. The porosity properties and surface area of these polymer networks can be finely tuned by using a linker with different geometries or strut length. These polymers show the Brunauer-Emmett-Tellerthe (BET) surface areas ranging from 592 to 1426 m2 g-1. The dominant pore sizes of the polymers on the basis of the different linker are located between 0.36 and 0.61 nm. Gas uptake increases with BET surface area and micropore volume, N4CMP-3 polymer can capture CO2 with a capacity of 3.62 mmol g-1 (1.05 bar and 273 K) among the obtained polymers. All of the polymers show high isosteric heats of CO2 adsorption (25.5-35.1 kJ mol-1), and from single component adsorption isotherms, IAST-derived ideal CO2/N2 (28.7-53.8), CO2/CH4 (4.6-5.2) and CH4/N2 (5.7-10.5) selectivity. Furthermore, N4CMPs exhibit the high CO2 adsorption capacity of 542-800 mg g-1 at 318 K and 50 bar pressure. These data indicate that these materials are a promising potential for clean energy application and environmental field.

Covalent Triazine Frameworks via a Low-Temperature Polycondensation Approach

Covalent triazine frameworks (CTFs) are normally synthesized by ionothermal methods. The harsh synthetic conditions and associated limited structural diversity do not benefit for further development and practical large-scale synthesis of CTFs. Herein we report a new strategy to construct CTFs (CTF-HUSTs) via a polycondensation approach, which allows the synthesis of CTFs under mild conditions from a wide array of building blocks. Interestingly, these CTFs display a layered structure. The CTFs synthesized were also readily scaled up to gram quantities. The CTFs are potential candidates for separations, photocatalysis and for energy storage applications. In particular, CTF-HUSTs are found to be promising photocatalysts for sacrificial photocatalytic hydrogen evolution with a maximum rate of 2647 μmol h-1  g-1 under visible light. We also applied a pyrolyzed form of CTF-HUST-4 as an anode material in a sodium-ion battery achieving an excellent discharge capacity of 467 mAh g-1 .

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.

Porous Carbon Materials Based on Graphdiyne Basis Units by the Incorporation of the Functional Groups and Li Atoms for Superior CO2 Capture and Sequestration

The graphdiyne family has attracted a high degree of concern because of its intriguing and promising properties. However, graphdiyne materials reported to date represent only a tiny fraction of the possible combinations. In this work, we demonstrate a computational approach to generate a series of conceivable graphdiyne-based frameworks (GDY-Rs and Li@GDY-Rs) by introducing a variety of functional groups (R = -NH₂, -OH, -COOH, and -F) and doping metal (Li) in the molecular building blocks of graphdiyne without restriction of experimental conditions and rapidly screen the best candidates for the application of CO₂ capture and sequestration (CCS). The pore topology and morphology and CO₂ adsorption and separation properties of these frameworks are systematically investigated by combining density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations. On the basis of our computer simulations, combining Li-doping and hydroxyl groups strategies offer an unexpected synergistic effect for efficient CO₂ capture with an extremely CO₂ uptake of 4.83 mmol/g at 298 K and 1 bar. Combined with its superior selectivity (13 at 298 K and 1 bar) for CO₂ over CH₄, Li@GDY-OH is verified to be one of the most promising materials for CO₂ capture and separation.

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

Soluble Polymers with Intrinsic Porosity for Flue Gas Purification and Natural Gas Upgrading

A soluble polymer with intrinsic microporosity, 2,4-diamino-1,3,5-triazine-functionalized organic polymer, is used for the first time as a solid adsorbent, providing an easy solution to overcome the fouling issue. Promising adsorption performances including good CO₂ adsorption capacity, excellent CO₂ /N₂ and CO₂ /CH₄ selectivities, high chemical and thermal stabilities, and easiness of preparation and regeneration are shown.

Construction of 3D homochiral metal–organic frameworks (MOFs) of Cd(ii): selective CO2adsorption and catalytic properties for the Knoevenagel and Henry reaction

Syntheses of two new homochiral, 3D metal–organic frameworks (MOFs) of Cd(ii) and the selective CO₂adsorption and catalytic properties of1has been demonstrated.

Targeted control over the porosities and functionalities of conjugated microporous polycarbazole networks for CO2-selective capture and H2 storage

Target controllable conjugated microporous polycarbazole networks with pyridine-, bipyridine-, and cyano-functionalized networks exhibit a large surface area and tunable gas uptake.

Hyper-crosslinked aromatic polymers with improved microporosity for enhanced CO2/N2 and CO2/CH4 selectivity

Two knitting polymers derived from highly rigid contorted monomers achieve improved microporosity for CO₂ storage and separation applications.

Multifunctional porous Tröger's base polymers with tetraphenylethene units: CO2adsorption, luminescence and sensing properties

A luminescent porous Tröger's base polymer with a tetraphenylethene unit was synthesized. It shows selective adsorption for CO₂and luminescent sensing abilities for Cu²⁺ions and picric acid.

Highly porous photoluminescent diazaborole-linked polymers: synthesis, characterization, and application to selective gas adsorption

Highly porous and photoluminescent diazaborole-linked polymers are targeted by boron–nitrogen bond formation through simple condensation reactions. The resultant polymers exhibit remarkable gas uptake and tunable photoluminescent properties.

"Stereoscopic" 2D super-microporous phosphazene-based covalent organic framework: Design, synthesis and selective sorption towards uranium at high acidic condition

So far, only five primary elements (C, H, O, N and B) and two types of spatial configuration (C2-C4, C6 and Td) are reported to build the monomers for synthesis of covalent organic frameworks (COFs), which have partially limited the route selection for accessing COFs with new topological structure and novel properties. Here, we reported the design and synthesis of a new "stereoscopic" 2D super-microporous phosphazene-based covalent organic framework (MPCOF) by using hexachorocyclotriphosphazene (a P-containing monomer in a C3-like spatial configuration) and p-phenylenediamine (a linker). The as-synthesized MPCOF shows high crystallinity, relatively high heat and acid stability and distinctive super-microporous structure with narrow pore-size distributions ranging from 1.0-2.1nm. The results of batch sorption experiments with a multi-ion solution containing 12 co-existing cations show that in the pH range of 1-2.5, MPCOF exhibits excellent separation efficiency for uranium with adsorption capacity more than 71mg/g and selectivity up to record-breaking 92%, and furthermore, an unreported sorption capacity (>50mg/g) and selectivity (>60%) were obtained under strong acidic condition (1M HNO3). Studies on sorption mechanism indicate that the uranium separation by MPCOF in acidic solution is realized mainly through both intra-particle diffusion and size-sieving effect.

Holey graphene frameworks for highly selective post-combustion carbon capture

Atmospheric CO₂ concentrations continue to rise rapidly in response to increased combustion of fossil fuels, contributing to global climate change. In order to mitigate the effects of global warming, development of new materials for cost-effective and energy-efficient CO₂ capture is critically important. Graphene-based porous materials are an emerging class of solid adsorbents for selectively removing CO₂ from flue gases. Herein, we report a simple and scalable approach to produce three-dimensional holey graphene frameworks with tunable porosity and pore geometry, and demonstrate their application as high-performance CO₂ adsorbents. These holey graphene macrostructures exhibit a significantly improved specific surface area and pore volume compared to their pristine counterparts, and can be effectively used in post-combustion CO₂ adsorption systems because of their intrinsic hydrophobicity together with good gravimetric storage capacities, rapid removal capabilities, superior cycling stabilities, and moderate initial isosteric heats. In addition, an exceptionally high CO₂ over N₂ selectivity can be achieved under conditions relevant to capture from the dry exhaust gas stream of a coal burning power plant, suggesting the possibility of recovering highly pure CO₂ for long-term sequestration and/or utilization for downstream applications.

Covalent organic frameworks based on Schiff-base chemistry: synthesis, properties and potential applications

Covalent organic-frameworks (COFs) are an emerging class of porous and ordered materials formed by condensation reactions of organic molecules.

Tunable porosity of nanoporous organic polymers with hierarchical pores for enhanced CO2 capture

We present a simple and convenient way to engineer the porosity of NOPs utilizing two crosslinkers with different length and various types of building blocks. The obtained polymers display hierarchical pore structures, remarkablely high CO₂ uptake capacities and sorption selectivity for CO₂/N₂.

BODIPY-containing porous organic polymers for gas adsorption

BODIPY-containing microporous organic polymers were synthesized via a Sonogashira–Hagihara coupling reaction of a BODIPY derivative and a range of aryl–alkyne monomers.

Tetraphenylethylene-based microporous organic polymers: insight into structure geometry, porosity, and CO2/CH4 selectivity

Tetraphenylethylene-based microporous organic polymers with tunable porosities were synthesized and their gas sorption capabilities were investigated.

Conjugated microporous polymer networks with adjustable microstructures for high CO2 uptake capacity and selectivity

A series of phenylene-based conjugated microporous polymers (CMPs) of the A₆ + M_x (x = 2, 3, 4, 6) type were synthesized.

Solvothermally synthesized nanoporous hypercrosslinked polyaniline: studies of the gas sorption and charge storage behavior

High surface area hypercrosslinked polyaniline samples synthesized by solvothermal method have shown efficient performance for gas sorption and charge storage.

Electron-withdrawing ability tunable polyphosphazene frameworks as novel heterogeneous catalysts for efficient biomass upgrading

Novel polyphosphazene frameworks as green heterogeneous catalysts are discovered for efficient production of 5-HMF from fructose, which is due to the unique cyclotriphosphazene unit and the electron-withdrawing nature of the polymer backbone.

A porous lanthanide metal–organic framework based on a flexible cyclotriphosphazene-functionalized hexacarboxylate exhibiting selective gas adsorption

This work presents a rare example of a permanently porous Ln-MOF based on a flexible hexacarboxylate exhibiting selective gas adsorption.

One-step assembly of a hierarchically porous phenolic resin-type polymer with high stability for CO2 capture and conversion

A hierarchically porous phenolic resin-type polymer with high stability has been rationally synthesized, which behaves as an excellent adsorbent and catalyst for CO₂ capture and conversion.

Aminal linked inorganic–organic hybrid nanoporous materials (HNMs) for CO2 capture and H2 storage applications

Cyclophosphazene based nitrogen-rich aminal-linked inorganic–organic hybrid nanoporous materials were synthesized by a Schiff-base condensation reaction, which captures 18.9 wt% of CO₂.

Dendrimer-like conjugated microporous polymers

Dendrimer-like carbazole-based conjugated microporous networks were designed and prepared by oxidative polymerization at room temperature.