Self‐Pillared Ultramicroporous Carbon Nanoplates for Selective Separation of CH 4 /N 2

Anisotropic Self-Assembly of Asymmetric Mesoporous Hemispheres with Tunable Pore Structures at Liquid-Liquid Interfaces

Asymmetric materials have attracted tremendous interest because of their intriguing physicochemical properties and promising applications, but endowing them with precisely controlled morphologies and porous structures remains a formidable challenge. Herein, a facile micelle anisotropic self-assembly approach on a droplet surface is demonstrated to fabricate asymmetric carbon hemispheres with a jellyfish-like shape and radial multilocular mesostructure. This facile synthesis follows an interface-energy-mediated nucleation and growth mechanism, which allows easy control of the micellar self-assembly behaviors from isotropic to anisotropic modes. Furthermore, the micelle structure can also be systematically manipulated by selecting different amphiphilic triblock copolymers as a template, resulting in diverse novel asymmetric nanostructures, including eggshell, lotus, jellyfish, and mushroom-shaped architectures. The unique jellyfish-like hemispheres possess large open mesopores (∼14 nm), a high surface area (∼684 m² g^-1), abundant nitrogen dopants (∼6.3 wt %), a core-shell mesostructure and, as a result, manifest excellent sodium-storage performance in both half and full-cell configurations. Overall, our approach provides new insights and inspirations for exploring sophisticated asymmetric nanostructures for many potential applications.

Recent Advances in Carbon-Based Adsorbents for Adsorptive Separation of Light Hydrocarbons

Light hydrocarbons (LHs) separation is an important process in petrochemical industry. The current separation technology predominantly relies on cryogenic distillation, which results in considerable energy consumption. Adsorptive separation using porous solids has received widespread attention due to its lower energy footprint and higher efficiency. Thus, tremendous efforts have been devoted to the design and synthesis of high-performance porous solids. Among them, porous carbons display exceptional stability, tunable pore structure, and surface chemistry and thus represent a class of novel adsorbents upon achieving the matched pore structures for LHs separations. In this review, the modulation strategies toward advanced carbon-based adsorbents for LHs separation are firstly reviewed. Then, the relationships between separation performances and key structural parameters of carbon adsorbents are discussed by exemplifying specific separation cases. The research findings on the control of the pore structures as well as the quantification of the adsorption sites are highlighted. Finally, the challenges of carbonaceous adsorbents facing for LHs separation are given, which would motivate us to rationally design more efficient absorbents and separation processes in future.

Nickel-Based Metal-Organic Frameworks for Coal-Bed Methane Purification with Record CH4 /N2 Selectivity

The enrichment and purification of coal-bed methane provides a source of energy and helps offset global warming. In this work, we demonstrate a strategy involving the regulation of the pore size and pore chemistry to promote the separation of CH₄ /N₂ mixtures in four nickel-based coordination networks, named Ni(ina)₂ , Ni(3-ain)₂ , Ni(2-ain)₂ , and Ni(pba)₂ , (where ina=isonicotinic acid, 3-ain=3-aminoisonicotinic acid, 2-ain=2-aminoisonicotinic acid, and pba=4-(4-pyridyl)benzoic acid). Among them, Ni(ina)₂ and Ni(3-ain)₂ can effectively separate CH₄ from N₂ with top-performing performance because of the suitable pore size (≈0.6 and 0.5 nm) and pore environment. Explicitly, Ni(ina)₂ exhibits the highest ever reported CH₄ /N₂ selectivity of 15.8 and excellent CH₄ uptake (40.8 cm³  g^-1 ) at ambient conditions, thus setting new benchmarks for all reported MOFs and traditional adsorbents. The exceptional CH₄ /N₂ separation performance of Ni(ina)₂ is confirmed by dynamic breakthrough experiments. Under different CH₄ /N₂ ratios, Ni(ina)₂ selectively extracts methane from the gaseous blend and produces a high purity of CH₄ (99 %). Theoretical calculations and CH₄ -loading single-crystal structure analysis provide critical insight into the adsorption/separation mechanism. Ni(ina)₂ and Ni(3-ain)₂ can form rich intermolecular interactions with methane, indicating a strong adsorption affinity between pore walls and CH₄ molecules. Importantly, Ni(ina)₂ has good thermal and moisture stability and can easily be scaled up at a low cost ($25 per kilogram), which will be valuable for potential industrial applications. Overall, this work provides a powerful approach for the selective adsorption of CH₄ from coal-bed methane.

Selective Synthesis of Carbon Nanorings via Asymmetric Intramicellar Phase-Transition-Induced Tip-to-Tip Assembly

The selective synthesis of energetically less favorable ring-shaped nanostructures by liquid phase synthetic chemistry is a huge challenge. Herein, we report a precise synthesis of carbon nanorings with a well-defined morphology and tunable thickness based on asymmetric intramicellar phase-transition-induced tip-to-tip assembly via mixing hydrophobic long-chain octadecanol and block copolymer F127. This orientational self-assembly depends on the hydrophobicity difference of the intermediate's surface, which triggers directional interactions that surpass the entropy cost of undesired connections and help assemble intermediates into defined ringlike structures. Based on a ringlike template, carbon nanorings with adjustable sizes can be attained by changing synthetic variables. More importantly, diverse units including crescentlike, podlike, and garlandlike nanostructures can also be created through controlling the kinetics of the self-assembly process. This discovery lays a solid foundation for the challenging construction of such a precise configuration on the nanoscale, which would not only promote fundamental studies but also pave the way for the development of advanced nanodevices with unique properties.

Separation and Purification of Hydrocarbons with Porous Materials

This Minireview focuses on the developments of the adsorptive separation of methane/nitrogen, ethene/ethane, propene/propane mixtures as well as on the separation of C8 aromatics (i.e. xylene isomers) with a wide variety of materials, including carbonaceous materials, zeolites, metal-organic frameworks, and porous organic frameworks. Some recent important developments for these adsorptive separations are also highlighted. The advantages and disadvantages of each material category are discussed and guidelines for the design of improved materials are proposed. Furthermore, challenges and future developments of each material type and separation processes are discussed.

Wiggling Mesopores Kinetically Amplify the Adsorptive Separation of Propylene/Propane

Adsorptive separation is an appealing technology for propylene and propane separation; however, the challenge lies in the design of efficient adsorbents which can distinguish the two molecules having very similar properties. Here we report a kinetically amplified separation by creating wiggling mesopores in structurally robust carbon monoliths. The wiggling mesopores with alternating wide and narrow segments afford a surface area of 413 m²  g^-1 and a tri-modal pore size distribution centered at 1.5, 4.2 and 6.6 nm, respectively. The synergistically kinetic and equilibrium effects were observed and quantitatively assessed, which together ensured a remarkable propylene/propane selectivity up to 39. This selectivity outperformed not only the available carbon adsorbents but also highly competitive among the dominated crystalline porous adsorbents. In addition, the wiggling mesoporous carbon adsorbent showed excellent dynamical separation stability, which ensured its great potential in practical molecular separations.