Molecular template-directed synthesis of microporous polymer networks for highly selective CO2 capture

A mechanochemical process to capture and separate carbon dioxide from natural gas using boron nitride nanosheets

Addressing climate change is a critical and pressing matter that requires immediate attention to mitigate its severe repercussions. In order to enhance the capture and separation of carbon dioxide from natural gas and nitrogen gas, it is imperative to develop new capture materials and more efficient storage processes. In this study, we introduce an innovative environmentally friendly storage and separation technique. Through a controlled mechanochemical process, a substantial amount of carbon dioxide (103.6 wt%) was successfully captured within boron nitride. This process also excels at effectively isolating carbon dioxide from a gas mixture containing natural gas (CH4) or nitrogen due to its superior adsorption selectivity for CO2 over the other two gases. The stored carbon dioxide can be released upon heating, and this procedure can be repeated several times (minimum four times), indicating a game changing process in CO2 gas capture and separation technology with the advantages of green, low cost and efficiency.

Highly Efficient Capture of Heavy Metal Ions on Amine-Functionalized Porous Polymer Gels

Porous polymer gels (PPGs) are characterized by inherent porosity, a predictable structure, and tunable functionality, which makes them promising for the heavy metal ion trap in environmental remediation. However, their real-world application is obstructed by the balance between performance and economy in material preparation. Development of an efficient and cost-effective approach to produce PPGs with task-specific functionality remains a significant challenge. Here, a two-step strategy to fabricate amine-enriched PPGs, NUT-21-TETA (NUT means Nanjing Tech University, TETA indicates triethylenetetramine), is reported for the first time. The NUT-21-TETA was synthesized through a simple nucleophilic substitution using two readily available and low-cost monomers, mesitylene and α, α′-dichloro-p-xylene, followed by the successful post-synthetic amine functionalization. The obtained NUT-21-TETA demonstrates an extremely high Pb2+ capacity from aqueous solution. The maximum Pb2+ capacity, qm, assessed by the Langmuir model was as high as 1211 mg/g, which is much higher than most benchmark adsorbents including ZIF-8 (1120 mg/g), FGO (842 mg/g), 732-CR resin (397 mg/g), Zeolite 13X (541 mg/g), and AC (58 mg/g). The NUT-21-TETA can be regenerated easily and recycled five times without a noticeable decrease of adsorption capacity. The excellent Pb2+ uptake and perfect reusability, in combination with a low synthesis cost, gives the NUT-21-TETA a strong potential for heavy metal ion removal.

A Novel Strategy to Enhance the Performance of CO2 Adsorption Separation: Grafting Hyper-cross-linked Polyimide onto Composites of UiO-66-NH2 and GO

Graphene oxide (GO) is widely used to improve the pore structure, dispersion capacity, adsorption selectivity, resistance to acids and bases, and thermal stability of metal-organic frameworks (MOFs). However, it remains a daunting challenge to enhance selectivity simply by modifying the pore surface polarity and producing a suitable pore structure for CO₂ molecules through a combination of GO with MOFs. Herein, we demonstrate a novel porous hyper-cross-linked polyimide-UiO-graphene composite adsorbent for CO₂ capture via in situ chemical knitting and condensation reactions. Specifically, a network of polyimides rich in carbonyl and nitrogen atoms with amino terminations was synthesized via the reaction of 4,4'-oxydiphthalic anhydride (ODPA) and 2,4,6-trimethyl-1,3-phenylenediamine (DAM). The product plays a crucial role in the separation of CO₂ from N₂. As expected, the resulting composite (PI-UiO/GO-1) exhibited a 3-fold higher CO₂ capacity (8.24 vs 2.8 mmol·g^-1 at 298 K and 30 bar), 4.2 times higher CO₂/N₂ selectivity (64.71 vs 15.43), and significantly improved acid-base resistance stability compared with those values of pristine UiO-66-NH_2. Furthermore, breakthrough experiments verified that the porous composites can effectively separate CO₂ from simulated fuel gas (CO₂/N₂ = 15/85 vol %) with great potential in industrial applications. More importantly, this strategy can be extended to prepare other MOF-based composites. This clearly advances the development of MOF-polymer materials for gas capture.

Acetic acid-mediated cellulose-based carbons: Influence of activation conditions on textural features and carbon dioxide uptakes

In this work, we developed a simple methodology for producing highly porous carbons. Herein, we combined the hydrothermal method with chemical activation to fabricate cellulose-based, melamine modified porous carbons, using acetic acid as an additive. The preparation conditions including activation temperature, activation time, and melamine ratio were varied to obtain an optimized adsorbent exhibiting efficient textural features and maximized carbon dioxide (CO₂) adsorption uptake. By varying the preparation conditions, high specific surface area (SSA) (1260-3019 m² g^-1), microporosity in the range of 0.21-1.13 cm³ g^-1, and a well-developed porous structure was obtained. The optimized adsorbent exhibits an excellent CO₂ adsorption uptake of 297.05 mg g^-1 (6.75 mmol g^-1) and 174.4 mg g^-1 (3.96 mmol g^-1) at 273 K and 298 K at 1 bar, respectively, due to the existence of ultra-micropores (<0.68 nm, < 0.81 nm), high SSA (3019 m² g^-1), and high nitrogen content (8%). Furthermore, the role of micropores in the CO₂ adsorption process suggests that micropores between 0.68 nm and 1 nm exhibit high CO₂ adsorption potential. Additionally, all synthesized carbons exhibited a high isosteric heat of adsorption (45 kJ mol^-1) and a greater affinity for adsorbed CO₂ species than nitrogen (N₂) molecules. Thus, as-fabricated porous carbon adsorbents are an effective competitor for CO₂ uptake applications to mitigate global warming.

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.

High-Charge Density Polymerized Ionic Networks Boosting High Ionic Conductivity as Quasi-Solid Electrolytes for High-Voltage Batteries

Solid-state electrolytes are actively sought for their potential application in energy storage devices, especially lithium metal rechargeable batteries. However, one of the key challenges in the development of solid-state electrolytes is their lower ionic conductivity compared with that of liquid electrolytes (10^-2 S cm^-1 at room temperature), where a large gap still exists. Therefore, the pursuit of high ionic conductivity equal to that of liquid electrolytes remains the main objective for the design of solid-state electrolytes. Here, we show a series of high-charge density polymerized ionic networks as solid-state electrolytes that take inspiration from poly(ionic liquid)s. The obtained quasi-solid electrolyte slice displays an astonishingly high ionic conductivity of 5.89 × 10^-3 S cm^-1 at 25 °C (the highest conductivity among those of the state-of-art polymer gel electrolytes and polymer solid electrolytes) and ultrahigh decomposition potential, >5.2 V versus Li/Li⁺, which are attributed to the continuous ion transport channel formed by an ultrahigh ion density and an enhanced chemical stability endowed by highly cross-linked networks. The Li/LiFePO₄ and Li/LiCoO₂ batteries (3.0-4.4 V) assembled with the solid electrolytes show high stable capacities of around 155 and 130 mAh g^-1, respectively. In principle, our work breaks new ground for the design and fabrication of the solid-state electrolytes in various energy conversion devices.

Controlling Pore Shape and Size of Interpenetrated Anion-Pillared Ultramicroporous Materials Enables Molecular Sieving of CO2 Combined with Ultrahigh Uptake Capacity

The separation of carbon dioxide (CO₂) from hydrocarbons is a critical process for the production of clean energy and high-purity chemicals. Adsorption based on molecular sieving is an energy-saving separation process; however, most of molecular sieves with narrow and straight pore channels exhibit low CO₂ uptake capacity. Here, we report that a twofold interpenetrated copper coordination network with a consecutive pocket-like pore structure, namely, SIFSIX-14-Cu-i (SIFSIX = hexafluorosilicate, 14 = 4,4'-azopyridine, i = interpenetrated) is a remarkable CO₂/CH₄ molecular sieving adsorbent which completely blocks the larger CH₄ molecule with unprecedented selectivity, whereas it has excellent CO₂ uptake (172.7 cm³/cm³) under the ambient condition. The exceptional separation performance of SIFSIX-14-Cu-i is attributed to its unique pore shape and functional pore surface, which combine a contracted pore window (3.4 Å) and a relatively large pore cavity decorated with high density of inorganic anions. Dispersion-corrected density functional theory calculation and neutron powder diffraction were performed to understand the CO₂ binding sites. The practical feasibility of SIFSIX-14-Cu-i for CO₂/CH₄ mixtures separation was validated by experimental breakthrough tests. This study not only demonstrates the great potential of SIFSIX-14-Cu-i for CO₂ separation but also provides important clues for other gas separations.

One-pot production of porous assemblies by PISA of star architecture copolymers: a simulation study

Porous vesicles can be produced in one-pot by the PISA of star architecture copolymers.

Waste wool derived nitrogen-doped hierarchical porous carbon for selective CO2 capture

In this work, N-doped hierarchical porous carbon has been successfully fabricated by KOH activation of waste wool. The optimal sample exhibits good CO₂ adsorption capacity under atmospheric pressure (1 bar), as well as excellent CO₂/N₂ selectivity.

Metal-Organic Frameworks for Heterogeneous Basic Catalysis

Great attention has been given to metal-organic frameworks (MOFs)-derived solid bases because of their attractive structure and catalytic performance in various organic reactions. The extraordinary skeleton structure of MOFs provides many possibilities for incorporation of diverse basic functionalities, which is unachievable for conventional solid bases. The past decade has witnessed remarkable advances in this vibrant research area; however, MOFs for heterogeneous basic catalysis have never been reviewed until now. Therefore, a review summarizing MOFs-derived base catalysts is highly expected. In this review, we present an overview of the recent progress in MOFs-derived solid bases covering preparation, characterization, and catalytic applications. In the preparation section, the solid bases are divided into two categories, namely, MOFs with intrinsic basicity and MOFs with modified basicity. The basicity can originate from either metal sites or organic ligands. Different approaches used for generation of basic sites are included, and each approach is described with representative examples. The fundamental principles for the design and fabrication of MOFs with basic functionalities are featured. In the characterization section, experimental techniques and theoretical calculations employed for characterization of basic MOFs are summarized. Some representive experimental techniques, such as temperature-programmed desorption of CO₂ (CO₂-TPD) and infrared (IR) spectra of different probing molecules, are covered. Following preparation and characterization, the catalytic applications of MOFs-derived solid bases are dealt with. These solid bases have potential to catalyze some well-known "base-catalyzed reactions" like Knoevenagel condensation, aldol condensation, and Michael addition. Meanwhile, in contrast to conventional solid bases, MOFs show some different catalytic properties due to their special structural and surface properties. Remarkably, characteristic features of MOFs-derived solid bases are described by comparing with conventional inorganic counterparts, keeping in mind the current opportunities and challenges in this field.

Iron Nanoclusters as Template/Activator for the Synthesis of Nitrogen Doped Porous Carbon and Its CO2 Adsorption Application

We propose a facile synthesis approach for nitrogen doped porous carbon and demonstrate a novel pore-forming method that iron nanoclusters act as a template or activator at different carbonization temperatures based on Fe³⁺-poly(4-vinyipyridine) (P4VP) coordination. P4VP will completely decompose even in an inert atmosphere, but under the coordination and catalysis of Fe³⁺, it can be converted to carbon at a very low temperature (400 °C). The aggregation of iron nanoclusters in the carbonization process showed different pore-forming methods at different temperatures. The as-prepared materials possess high specific surface area (up to 1211 m² g^-1), large pore volume (up to 0.96 cm³ g^-1), narrow microporosity, and high N content (up to 9.9 wt %). Due to these unique features, the materials show high CO₂ uptake capacity and excellent selectivity for CO₂/N₂ separation. The CO₂ uptake capacity of NDPC-2-600 is up to 6.8 and 4.3 mmol g^-1 at 0 and 25 °C; the CO₂/N₂ (0.15/0.85) selectivity at 0 and 25 °C also reaches 18.4 and 15.2, respectively.

Multifunctional Porous Organic Polymers: Tuning of Porosity, CO2, and H2 Storage and Visible-Light-Driven Photocatalysis

A series of porous organic polymers (POPs) were fabricated based on a boron dipyrromethene (BODIPY) core. The variation of the substituents in the BODIPY core and the fine-tuning of the Sonogashira polycondenzation reaction with 1,3,5-triethynylbenzene led to the formation of POPs with a wide range of surface area and porosity. A 10-fold increase in surface area from 73 m² g^-1 in BDT1a polymer to 1010 m² g^-1 in BDT3 was obtained. Simultaneously, the porosity was changed from mesoporous to ultramicroporous. The surface area of BDT3 turned out to be the highest reported so far for BODIPY-based POPs. Molecular dynamics simulation coupled with Grand Canonical Monte Carlo simulations revealed the effect of substituents alkyl groups and rigidity of the core structures on the surface properties of the POPs. Detailed gas adsorption studies of the polymers revealed a high uptake of CO₂ and H₂. The highest uptake capacity of 16.5 wt % for CO₂ at 273 K and 2.2 wt % for H₂ at 77 K was observed for BDT3 at 1 bar pressure. The isosteric heat of adsorption (Q_st) of BDT3 for CO₂ was found to be as high as 30.6 kJ mol^-1. Electron paramagnetic resonance studies revealed the generation of singlet oxygen upon photoexcitation of these polymers. The BODIPY-based POPs turned out to be excellent catalysts for visible-light-driven photo-oxidation of thioanisole. The present study establishes BODIPY-based POPs as a new class of multifunctional materials.

Covalent Triazine-Based Frameworks with Ultramicropores and High Nitrogen Contents for Highly Selective CO2 Capture

Porous organic frameworks (POFs) are a class of porous materials composed of organic precursors linked by covalent bonds. The objective of this work is to develop POFs with both ultramicropores and high nitrogen contents for CO2 capture. Specifically, two covalent triazine-based frameworks (CTFs) with ultramicropores (pores of width <7 Å) based on short (fumaronitrile, FUM) and wide monomers (1,4-dicyanonaphthalene, DCN) were synthesized. The obtained CTF-FUM and CTF-DCN possess excellent chemical and thermal stability with ultramicropores of 5.2 and 5.4 Å, respectively. In addition, they exhibit excellent ability to selectively capture CO2 due to ultramicroporous nature. Especially, CTF-FUM-350 has the highest nitrogen content (27.64%) and thus the highest CO2 adsorption capacity (57.2 cc/g at 298 K) and selectivities for CO2 over N2 and CH4 (102.4 and 20.5 at 298 K, respectively) among all CTF-FUM and CTF-DCN. More impressively, as far as we know, the CO2/CH4 selectivity is larger than that of all reported CTFs and ranks in top 10 among all reported POFs. Dynamic breakthrough curves indicate that both CTFs could indeed separate gas mixtures of CO2/N2 and CO2/CH4 completely.

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.

Polymerized Ionic Networks with High Charge Density: Quasi-Solid Electrolytes in Lithium-Metal Batteries

Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10(-3) S cm(-1) at 22°C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

Design and fabrication of mesoporous heterogeneous basic catalysts

Recent advances in mesoporous solid bases were reviewed, and fundamental principles of how to fabricate efficient basic catalysts were highlighted.