Nanoporous Polymer Research Articles

Room-Temperature Synthesis of a Fluorine-Functionalized Nanoporous Organic Polymer for Highly Efficient SF6 Adsorption and Separation.

Sulfur hexafluoride (SF6) is widely used in the power industry and significantly contributes to the greenhouse effect, necessitating the development of efficient materials for SF6 capture, particularly fluorine-containing materials. However, existing fluorine-containing materials often require complex monomers and high synthesis temperatures. Herein, we report the synthesis of a fluorine-functionalized carbazole-based nanoporous organic polymer (CNOP-7) at room temperature, using commercially available 4,4'-bis(9H-carbazole-9-yl)-1,1'-biphenyl and 1,1,1-trifluoroacetone. CNOP-7 contains 14.7% fluorine atoms and exhibits a high specific surface area of 1270 m2·g-1, demonstrating excellent SF6 adsorption and separation performance. The SF6/N2 selectivity of CNOP-7 reaches 107 at 273 K and 73 at 298 K. Furthermore, dynamic breakthrough experiments confirm that CNOP-7 can efficiently and repeatedly separate SF6 from SF6/N2 mixtures. Molecular simulations reveal the mechanism behind its efficient separation. This work offers fresh perspectives on the development and fabrication of adsorbents for efficient SF6 sequestration.

Reconfigurable Antireflection Coatings Enabled by PDMS Oligomer Infusion in Templated Nanoporous Polymer Films.

The diffusion of uncured polydimethylsiloxane (PDMS) oligomers out of bulk PDMS elastomers is usually detrimental to many biomedical and microfluidic applications due to the inevitable contamination of the contacting fluids and substrates. Here, we transform this detrimental process into an enabling technology for achieving novel reconfigurable antireflection (AR) coatings, which are of great technological importance in the development of new nano-optical and optoelectronic applications. Self-assembled monolayer silica colloidal crystals are first used as sacrificial templates in fabricating nanoporous polymer AR coatings. When air in the templated nanopores is replaced with infused PDMS oligomers simply by pressing a PDMS stamp on a nanoporous AR film, the original antireflection conditions are lost, and the coating transforms from a low-reflection configuration to a high-reflection state. The original antireflection performance can be fully recovered by dissolving the infused oligomers in the appropriate solvents (e.g., hexane). This novel tuning mechanism for achieving reconfigurable AR properties has been confirmed by systematic investigations using various microscopes, optical spectroscopy, nanoindentation, thermomechanical tests, and X-ray photoelectron spectroscopy. Complex micropatterns with micrometer-scale spatial resolution and drastically different AR performances can be easily printed on nanoporous AR films by using a soft lithography-based microcontact printing process. Numerical finite-difference time-domain simulations match well with experimental antireflection measurements and reveal a linear relationship between the optical transmission and the amount of infused PDMS oligomers in nanopores.

Highly Selective SO2 Capture by Triazine-Functionalized Triphenylamine-Based Nanoporous Organic Polymers.

The emissions of sulfur dioxide (SO2) from combustion exhaust gases pose significant risks to public health and the environment due to their harmful effects. Therefore, the development of highly efficient adsorbent polymers capable of capturing SO2 with high capacity and selectivity has emerged as a critical challenge in recent years. However, existing polymers often exhibit poor SO2/CO2 and SO2/N2 selectivity. Herein, we report two triazine-functionalized triphenylamine-based nanoporous organic polymers (ANOP-6 and ANOP-7) that demonstrate both good SO2 uptake and high SO2/CO2 and SO2/N2 selectivity. These polymers were synthesized through cost-effective Friedel-Crafts reactions using cyanuric chloride, 3,6-diphenylaminecarbazole, and 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene. The resultant ANOPs are composed of triazine and triphenylamine units and feature an ultramicroporous structure. Remarkably, ANOPs exhibit impressive adsorption capacities for SO2, with uptakes of approximately 3.31-3.72 mmol·g-1 at 0.1 bar, increasing to 9.52-9.94 mmol·g-1 at 1 bar. The static adsorption isotherms effectively illustrate the ability of ANOPs to separate SO2 from SO2/CO2 and SO2/N2 mixtures. At 298 K and 1 bar, ANOP-6 shows outstanding selectivity toward SO2/CO2 (248) and SO2/N2 (13146), surpassing all previously reported triazine-based nanoporous organic polymers. Additionally, dynamic breakthrough tests demonstrate the superior separation properties of ANOPs for SO2 from an SO2/CO2/N2 mixture. ANOPs exhibit a breakthrough time of 73.1 min·g-1 and a saturated SO2 capacity of 0.53 mmol·g-1. These results highlight the exceptional adsorption properties of ANOPs for SO2, indicating their promising potential for the highly efficient capture of SO2 from flue gas.

Nanoporous, Ultrastiff, and Transparent Plastic-like Polymer Hydrogels Enabled by Hydrogen Bonding-Induced Self-Assembly.

Most natural supporting tissues possess both exceptional mechanical strength, a significant amount of water, and the anisotropic structure, as well as nanoscale assembly. These properties are essential for biological processes, but have been challenging to emulate in synthetic materials. In an effort to achieve simultaneous improvement of these trade-off features, a hydrogen bonding-induced self-assembly strategy was introduced to create nanoporous plastic-like polymer hydrogels. Multiple hydrogen bonding-mediated networks and nanoporous orientation structures endow transparent hydrogels with remarkable mechanical robustness. They exhibit Young's modulus of up to 223.7 MPa and a breaking strength of up to 10.3 MPa, which are superior to those of most common polymer hydrogels. The uniform porous nanostructures of hydrogen-bonded hydrogels contribute to a significantly larger specific surface area compared to conventional hydrogels. This allows for the retention of high mechanical properties in environments with a high water content of 70 wt %. A rubbery stage is observed during the heating process, which can reverse and reshape the manufacture of objects with various desired 2D or 3D shapes using techniques such as origami and kirigami. Finally, as a proof-of-concept, the outstanding mechanical properties of poly(MAA-co-AA-co-NVCL) hydrogel, combined with its high water content, make it suitable for applications such as smart temperature monitors, multilevel information anticounterfeiting, and artificial muscles.

Vibration isolation performance of silica aerogel blankets and boards, fumed silica, polymer aerogel and nanofoams

Buildings are often constructed on a continuous layer of vibration isolation to reduce vibrations and structure-borne noise. There are many vibration isolation products (rubber mats, textiles, polymer foams), but none fulfils all requirements in terms of load-bearing capacity, performance, and cost. In previous work, we have shown that silica aerogel particle beds display a low resonance frequency and correspondingly high vibration isolation performance. Loose silica aerogel granules are not a practical vibration isolation solution. In order to guide the future development of dedicated vibration isolation products based on aerogels, we determine the vibro-acoustic properties of a variety of existing commercial and R&D stage mesoporous composites, that have been developed for thermal insulation applications. The sample set includes monolithic aerogels (polyurethane), silica aerogel composites (aerogel – fibers, aerogel impregnated foams, aerogel bound with polymer foam), glued fumed silica-fiber boards, and nanoporous polymer foam composite boards. The silica aerogel and fumed silica composites display low resonance frequencies (down to 8 Hz for 40 mm, strongly dependent on composite type) and a low dynamic stiffness and loss factor over a wide range of static loads. The polymer aerogel, nanoporous foam and polymer-bound silica aerogel granule board all display higher resonance frequencies, consistent with their higher static stiffness. Although optimized for thermal insulation rather than vibration isolation, many of the tested silica aerogel and fumed silica composites are competitive with the best vibration isolation products on the market in terms of vibration isolation performance. The diversity of materials tested informs on which approaches, materials, and materials combinations are most promising to target vibration isolation.

Ultrathin Ionic Diodes with Electrostatically Heterogeneous Hybrid Interfaces of Nanoporous SiO2 Nanofilms and Polymer Layer-by-Layer Multilayers.

Nanofluidic ionic diodes have attracted much attention due to their unique functions as unidirectional ion transportation ability and promising applications from molecular sensing, and energy harvesting to emerging neuromorphic devices. However, it remains a challenge to fabricate diode-like nanofluidic systems with ultrathin film thickness <100nm. Herein the formation of ultrathin ionic diodes from hybrid nanoassemblies of nanoporous (NP) SiO2 nanofilms and polyelectrolyte layer-by-layer (LbL) multilayers is described. Ultrathin ionic diodes are prepared by integrating polyelectrolyte multilayers onto photo-oxidized NP SiO2 nanofilms obtained from silsesquioxane-containing block copolymer thin films as a template. The obtained ultrathin ionic diodes exhibit ion current rectification (ICR) properties with high ICR factor = ≈20 under low ionic strength and asymmetric pH conditions. It is concluded that this ICR behavior arises from effective ion accumulation and depletion at the interface of NP SiO2 nanofilms and LbL multilayers attributed to high ion selectivity by combining the experimental data and theoretical calculations using finite element methods. These results demonstrate that the hybrid nano assemblies of NP SiO2 nanofilms and polyelectrolyte LbL multilayers have potential applications for (bio)sensing materials and integrated ionic circuits for seamless connection of human-machine interfaces.

Highly selective separation of sulfur dioxide in a triphenylamine-based nanoporous organic polymer

The urgent need for effective SO2 capture materials has driven research into the development of novel nanoporous organic polymers (NOPs). Herein, we developed a triphenylamine-based nanoporous organic polymer, designated as ANOP-5, through the self-condensation of an AB2 triphenylamine monomer. The adsorption/separation properties of SO2 and CO2 are comparatively evaluated through the investigation of static gas adsorption isotherms. At 273 K and 100 kPa, ANOP-5 displays a high SO2 adsorption capacity of 399 cm3 g−1 and a high selectivity of 388 for SO2/CO2, with a molar ratio of SO2 to CO2 at 10/90. The exceptional performance of desulfurization is attributed to the strong interaction between ANOP-5 and SO2, in addition to the ultramicroporous structure. These findings are further supported by the dispersion-corrected density functional theory calculations. This study contributes valuable insights into the design and preparation of NOPs with high gas adsorption properties, particularly for addressing environmental pollution challenges related to SO2 emissions.

Exploring Nanomaterials for Hydrogen Storage: Advances, Challenges, and Perspectives.

Hydrogen energy heralded for its environmentally friendly, renewable, efficient, and cost-effective attributes, stands poised as the primary alternative to fossil fuels in the future. Despite its great potential, the low volumetric density presents a formidable challenge in hydrogen storage. Addressing this challenge necessitates exploring effective storage techniques for a sustainable hydrogen economy. Solid-state hydrogen storage in nanomaterials (physically or chemically) holds promise for achieving large-scale hydrogen storage applications. Such approaches offer benefits, including safety, compactness, lightness, reversibility, and efficient generation of pure hydrogen fuel under mild conditions. This article presents solid-state nanomaterials, specifically nanoporous carbons (activated carbon, carbon fibers), metal-organic frameworks, covalently connected frameworks, nanoporous organic polymers, and nanoscale metal hydrides. Furthermore, new developments in hydrogen fuel cell technology for stationary and mobile applications have been demonstrated. The review outlines significant advancements thus far, identifies key barriers to practical implementation, and presents a perspective for future sustainable energy research. It concludes with recommendations to enhance hydrogen storage performance for cost-effective and long-lasting utilization.

Tailoring NH3 Sensing Responsiveness through Amine Modification of Imine-Based Nanoporous Covalent Organic Polymer

Tailoring NH₃ Sensing Responsiveness through Amine Modification of Imine-Based Nanoporous Covalent Organic Polymer

Voltage-modulated polymer nanopore field-effect transistor for multi-sized nanoparticle detection

Solid-state nanopores offer a range of distinct advantages over biological nanopores, such as structural diversity and greater stability and durability; this makes them highly promising for high-resolution nanoparticle sensing. Biological nanopores can exhibit gating characteristics with stress-responsive switches and can demonstrate specificity toward particular molecules. Drawing inspiration from biological nanopores, this paper introduces a novel polymer nanopore with field-effect characteristics, leveraging a conductive polymer in its construction to showcase intriguing gating behavior. Notably, in this device, the polymer layer serves as the gate, enabling precise control over the source–drain current response inside and outside the pore by simply adjusting the gate voltage. This unique feature allows fine-tuning of the nanopore’s sensitivity to nanoparticles of varying sizes and facilitates its operation in multiple modes. Experimental results reveal that the developed polymer nanopore field-effect transistor demonstrates remarkable selectivity in detecting nanoparticles of various sizes under different applied voltages. The proposed single device demonstrates the exceptional ability to detect multiple types of nanoparticle, showcasing its immense potential for a wide range of applications in biological-particle analysis and medical diagnostics.

Engineering of uniform dispersed Ni nanoparticles supported on carbon nanosheets for reduction of Nitroarenes to Aminoarenes

Facile synthesis of uniform supported metal catalysts is of great significance yet remains challenging for sustainable catalysis. Herein, a nanopore confinement strategy is developed to efficiently anchor metal ions in suitably sized polymer nanopores via strong coordinate bonds and ensure successful fabrication of uniform carbon-supported metal nanoparticles. Specifically, Ni2+-coordinated polydopamine (PDA) mesoporous layer was coated on GO nanosheets for the confinement of the nickel atoms (GO@PDA-Ni-x, x means pore size of PDA layer), resulting Ni@C-x nanosheets catalysts with uniformly dispersed Ni nanoparticles after pyrolysis in H2/Ar atmosphere. Characterization methods including SEM, TEM, and XPS reveal the intrinsic formation mechanism and physicochemical details. In the catalytic reaction of NaBH4-mediated hydrogenation of 4-nitrophenol (4-NP), the obtained Ni/C-10 exhibits exceptional catalytic performance with a rapid rate constant (0.686 min−1), outperforming many previously reported metal catalysts. Moreover, the catalytic activity remains almost unchanged after being recycled five times, proving the prominent stability. This work opens up an innovative avenue for rational design and synthesis of supported catalysts with controllable size for broad catalytic applications.

ZIF-8 functionalized S-tapered fiber-optic sensor for polystyrene nanoplastics detection by electrostatic adsorption

Microplastic (MP) residues in marine have become an increasingly serious environmental pollution issue, and in recent years the detection of MPs in marine started to attract worldwide research interests. Optical-fiber-based environmental sensors have been extensively employed for their several merits such as high sensitivity, pressure resistance, compactness and ease of constructing communication networks. However, fiber-optic refractive index sensors are not specifically developed for distinguishing MPs from other inorganic particles suspended in water. In this paper, an metal-organic framework (MOF) ZIF-8 functionalized S-tapered fiber (STF) sensor is proposed for specific detection of polystyrene nanoplastics (PSNPs) in aqueous environment. ZIF-8 coordination nanoporous polymers with different film thickness were immobilized over the surface of the fabricated STF structure based on self-growth technique and yielding a large surface area over the sensor surface. High sensitivity detection can be achieved by converting the concentration perturbation of PSNPs into evanescent waves over the ZIF-8 functionalized STF surface through the strong electrostatic adsorption effect and π-π stacking, while the fabricated sensor is insensitive to gravels with silica as the primary component in water. It is found that the proposed detector with 18 film layers achieves a sensitivity up to 114.1353nm/%(w/v) for the PSNPs concentration range of 0.01 %(w/v) to 0.08 %(w/v).

Biphasic nanocomposite films of polypyrrole and poly(3,4-ethylene dioxythiophene) using a surface-tethered dopant strategy

Using a newly invented surface-tethered dopant approach for the electrochemical polymerization growth of conductive polymer films, nanocomposites are created consisting of two distinct phases of polypyrrole (PPy) and Poly(3,4-ethylene dioxythiophene) (PEDOT). The growth of the conductive nanocomposite films takes advantage of the unique way in which a conductive polymer film forms when grown using a surface-tethered dopant, starting out as a highly nanoporous film that gradually becomes more and more solid as additional polymer deposition occurs preferentially within the nanopores rather than at the films outer surface. Nanocomposite films can thus be fabricated simply and controllably by first growing one nanoporous conductive polymer film followed by the deposition of a second conductive polymer within the nanopores of the first. This study investigates the morphological and electrochemical properties of nanocomposite films grown using a surface-tethered dopant and how these properties are affected by simple changes in electrochemical polymerization parameters.

Two-Dimensional Nanoporous Cross-linked Polymer Networks as Emerging Candidates for Gas Adsorption.

This paper illustrates the gas adsorption properties of newly synthesized nanoporous cross-linked polymer networks (CPNs). All synthesized CPNs possess N-rich functional groups and are used for the utilization of carbon dioxide and methane. Good gas adsorption and selectivities are obtained for all of the samples. Among the materials, HEREON2 outperforms better selectivity for methane separation from nitrogen rather than zeolites, activated carbons, molecular sieves, covalent organic frameworks, and metal-organic frameworks (MOFs). The accessibility of the N-rich functionalities makes these materials potential candidates for the separation of hydrocarbons via increased polarizabilities. High-pressure adsorption experiments showed that the synthesized two-dimensional nanoporous materials also have a high affinity toward carbon dioxide. HEREON2 powders showed an increased experimental CO2/N2 selectivity of ∼25,000 at 50 bar due to the presence of nitrogen groups in the structure. Fourier-transform infrared spectroscopy (FTIR), solid-state NMR, X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were applied for the characterization of the synthesized nanoporous CPNs. The results show a potential new pathway for future CPN membrane development.

Multifunctional Umbrella: In Situ Interface Film Forming on the High-Voltage LiCoO2 Cathode by a Tiny Amount of Nanoporous Polymer Additives for High-Energy-Density Li-Ion Batteries.

The LiCoO2 (LCO) cathode is foreseen for extensive commercial applications owing to its high specific capacity and stability. Therefore, there is considerable interest in further enhancing its specific capacity by increasing the charging voltage. However, single-crystal LCO suffers from a significant capacity degradation when charged to 4.5V due to the irreversible phase transition and unstable structure. Herein, an ultra-small amount (0.5%wt. in the electrode) of multi-functional PIM-1 (a polymer with intrinsic microporosity) additive is utilized to prepare a kind of binder-free electrode. PIM-1 modulates the solvation structure of LiPF6 due to its unique structure, which helps to form a stable, robust, and inorganic-rich cathod-eelectrolyte interphase (CEI) film on the surface of LCO at a high voltage of 4.5V. This reduces the irreversible phase transition of LCO, thereby enhancing the cyclic stability and improving the rate performance, providing new perspectives for the electrodes fabrication and improving LCO-based high-energy-density cathodes.

Two-dimensional monolayer from organic molecules F4-TCNQ via DFT calculations

Conjugated microporous polymers is a class of organic nanoporous polymers in which the pores can be easily controlled by molecule design. Here we present a new class of 2D structure based on F4-TCNQ molecules. Using ab initio calculations, the possibilities for the formation of such 2D materials based on F4-TCNQ molecules are studied as well. Among considered structures only two were selected as the most preferable for 2D layer formation. Predicted monolayers were analyzed on thermal stability, electronic, optical and mechanical properties. Combination of stability, elasticity and semiconducting band gap make suggested monolayers promising candidate for fabrication of elements of flexible and controllable optoelectronics.

Nanoporous hypercrosslinked polymers as cost-effective catalysts to significantly promote the CO2 absorption performance of water-lean solvents for post-combustion CO2 capture

In most cases, the slow CO2 sorption kinetics of water-lean solvents—which include low-volatile organic diluents—are the limiting factor when it comes to post-combustion CO2 capture. This study offers a solution by suggesting the use of catalysts based on nanoporous hypercrosslinked polymers (HCPs) to improve the removal efficiency of water-lean solvents based on diethanolamine (DEA) and to increase CO2 mass transfer. Simple and inexpensive monomers were used to prepare three HCPs: HCP-C, HCP-S, and HCP-B, which stand for benzene, polystyrene, and carbazole, respectively. Blends of DEA and Glycerol (Gly) were used to disperse these polymers. Addition of 0.5 wt% HCP to a solvent mixture of 20% DEA and 30% Gly considerably boosts removal efficiency and increases the amount of CO₂ that can be absorbed until the breakthrough point by as much as 3000%, according to the results. Additionally, various gas flow rates, DEA concentrations, and glycerol concentrations were also investigated to determine the HCP-C catalytic effect on the CO2 absorption. A volumetric overall mass transfer coefficient enhancement of up to 319 % is possible in the investigated ranges when using HCP-C, according to the findings. Moreover, a possible catalytic mechanism was suggested.

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

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

Synthesis of triphenylamine-based nanoporous organic polymers for highly efficient capture of SO2 and CO2

Two triphenylamine-based nanoporous organic polymers were synthesized through the self-condensation of AB2 monomers. These polymers exhibit promising potential for capturing toxic gases and contaminants due to their highly effective uptake of SO2.

Photo-responsive nanoporous liquid crystal polymer films for selective dye adsorption.

Photo-responsive nanoporous polymer films (AZOF-R(NC6)) have been developed by a template method based on a hydrogen-bonding supramolecular liquid crystal (LC) and a light-sensitive azobenzene LC crosslinker in this work. Anionic nanopores were obtained after the removal of template NC6 using KOH solution. The AZOF-R(NC6) demonstrates charge-selective dye adsorption and the maximum adsorption capacity for Rh6G is 504.6 mg g-1. The AZOF-R(NC6) film without UV light treatment shows a 32% higher adsorption capacity for Rh6G than the AZOF-R(NC6) film treated with UV light within the initial 10 min. In addition, UV light can trigger the release of the adsorbed dye from the polymer film due to the pore size change arising from the trans-cis isomerization. Besides, the used polymer film can be effectively regenerated using a HCl solution. Such functional polymer films with highly ordered nanopores and photo-responsive properties hold great promise in selective adsorption and mass separations.