Efficient ethylene purification by a robust ethane-trapping porous organic cage

Discovery of a molecular adsorbent for efficient CO2/CH4 separation using a computation-ready experimental database of porous molecular materials

The development and sharing of computational databases for metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have significantly accelerated the exploration and application of these materials. Recently, molecular materials have emerged as a notable subclass of porous materials, characterized by their crystallinity, modularity, and processability. Among these, macrocycles and cages stand out as representative molecules. Experimental discovery of a target molecular material from a vast possibility of structures for defined applications is generally impractical due to high experimental costs. This study presents the most extensive Computation-ready Experimental (CoRE) database of macrocycles and cages (MCD) to date, comprising 7939 structures. Using the MCD, we conducted simulations of binary CO2/CH4 competitive adsorption under conditions relevant to industrial applications. These simulations established a structure-property-function relationship, enabling the identification of materials with potential for CO2/CH4 separation. Among them, a macrocycle, NDI-Δ, exhibited promising CO2 adsorption capacity and selectivity, as confirmed by gas sorption and breakthrough experiments.

Regulating the Dynamics of Interpenetrated Porous Frameworks for Inverse C2H6/C2H4 Separation at Elevated Temperature

Selective adsorption of ethane (C2H6) from mixtures containing ethylene (C2H4) is of interest for the direct production of high purity C2H4. However, the extremely similar molecular properties of these gases make this process challenging, particularly at elevated temperatures, an implication of saved energy consumption. To address such challenge, we present a new approach for regulating the temperature-dependent dynamics in hydrogen-bonded interpenetrated frameworks. As a single H-bond linked interpenetrated porous framework, NTU-101-NH2 exhibits emerging structural dynamics in response to C2H6 (37 kPa) and C2H4 (53 kPa) and has shown a record ability to produce polymer-grade C2H4 (15.7 mL g-1) at 328 K, as the shifting of the interpenetrated frameworks here requires a relatively weak stimulus, allowing the optimization of adsorption at a higher temperatures range. Meanwhile, the robust and conveniently prepared NTU-101-NH2 shows good cyclic separation performance. In comparison, the framework response of the percussor NTU-101, connected by three H-bonds, occurs at 293 K and has a moderate separation ability (10.2 mL g-1). This work showcases the first adsorbent for direct C2H4 purification at elevated temperatures, and the insights into the hydrogen-bonded frameworks will pave the way for designing soft families capable of challenging separations with reduced energy requirements.

Superhydrophobic Molecular Selector for Efficient Separation of Ethane over Ethylene under Dry and Humid Conditions

Exploring humidity-resistant, ethane-selective adsorbents for the one-step purification of polymer-grade (>99.95%) ethylene from ethane-ethylene mixtures is of great importance, yet remains a significant challenge. To address this challenge, we present a novel strategy for constructing a "superhydrophobic molecular selector" (SMS) based on a porous organic cage (POC), which features a superhydrophobic outer surface and an inner cavity with multiple ethane-selective functional sites. The resulting SMS-POC-1 demonstrates excellent C2H6 adsorption capacity (97 cm3 g-1 at 298 K) and C2H6/C2H4 selectivity (Sads = 2.40 at 298 K), offering a superior trade-off between ethane adsorption capacity and C2H6/C2H4 adsorption selectivity among all C2H6-selective adsorbents. Especially, breakthrough experiments demonstrate that SMS-POC-1 efficiently produces polymer-grade C2H4 from C2H6/C2H4 mixtures at 60% relative humidity (RH), making it the highest-selectivity adsorbent reported to date that can stably operate in a humid environment. The combination of experimental results and theoretical calculations reveals that the coexistence of a superhydrophobic outer surface and synergistic C-H···π interactions and hydrogen-bonding sites accounts for the high C2H6/C2H4 separation performance under humid conditions for SMS-POC-1. Our work thus not only demonstrates a general strategy for guiding the design of humidity-resistant adsorption-separation materials but also presents a promising candidate for potential applications in hydrocarbon separation.

Preparation of a Homochiral Porous Organic Cage RCC2-S-Bonded Silica as a Stationary Phase for High-Performance Liquid Chromatography Enantioseparation

In this work, a reduced homochiral porous organic cage (RCC2-S)-based chiral stationary phase (CSP), RCC2-S@SiO2-SH, was prepared by bonding RCC2-S on thiolated silica (SiO2-SH) via a thiol-ene click reaction. The CSP (RCC2-S@SiO2-SH) showed excellent enantioseparation in both normal-phase HPLC (NP-HPLC) and reversed-phase HPLC (RP-HPLC) modes, effectively separating various chiral compounds, including alcohols, esters, ketones, amines, imidazoles, epoxides, and organic acids. As a result, 12 racemates were enantioseparated under NP-HPLC, and 17 racemates were enantioseparated under RP-HPLC. The CSP also exhibited good complementarity in chiral separation with commercial Chiralpak AD-H, Chiralcel OD-H, and the previously reported chiral POC CC19-R columns, successfully separating some racemates that remained unresolved or poorly resolved on these three columns. Additionally, the fabricated RCC2-S@SiO2-SH packed column demonstrated good reproducibility and stability. The relative standard deviations (RSDs) of retention time and resolution value were less than 0.5% and 1.5%, respectively, after the column had been subjected to hundreds of injections. This work indicates that chiral porous organic cages have great potential for the separation of enantiomers in HPLC.

A triply linked propellane-nanoring hybrid serving as a good host

A novel propellane-nanoring hybrid, TPPTI-[9]CMP, was synthesized by triply combining [9]cyclo-meta-phenylene ([9]CMP) with triperyleno[3,3,3]propellane triimides (TPPTI). This structure features two [9]CMP subunits, which necessarily fill the voids of TPPTI and promote assembly of the hybrid to form a porous superstructure held together by attractive dispersion between the [9]CMP subunits of neighboring molecules. In the structure, three large spatial cavities are formed, which allow efficient binding of up to three C60 within a single hybrid. Transient absorption spectroscopy revealed that TPPTI-[9]CMP and C60 interact with each other to form a stable complex and produce long-lived triplet states. Notably, the hybrid can adsorb ethane (C2H6) with very excellent selectivity over ethylene (C2H4), leading to a highly selective C2H6/C2H4 separation.

Efficient One-Step Purification of Methanol-to-Olefin Products Using a Porphyrinyl MOF to Achieve Record C2H4 and C3H6 Productivity

The separation of methanol-to-olefin (MTO) products to obtain high-purity ethylene (C2H4) and propylene (C3H6) is a challenging yet critical task, as these compounds are essential industrial raw materials for polymer synthesis. However, developing adsorbents with high selectivity and productivity for C2H4/C3H6 remains a significant challenge and an urgent necessity. In this study, a porphyrinyl metal-organic framework (MOF), Al-TCPP, was developed for the simultaneous recovery of C3H6 and C2H4 through a one-step adsorption-desorption process. Benefiting from its well-developed microporous structure and abundant N- and O-accessible sites, Al-TCPP demonstrated exceptional adsorption capacities and selectivity for C3H6 and ethane (C2H6) over C2H4 under ambient conditions. The adsorption capacities (in cm3·g-1) reached 162.4 for C3H6 and 118.5 for C2H6 at 298 K and 100 kPa. The ideal adsorbed solution theory (IAST) selectivity values for C3H6/C2H4 and C2H6/C2H4 were 10.1 and 1.8, respectively. Thermodynamic studies and theoretical calculations revealed stronger interactions between C2H6 and C3H6 molecules with the Al-TCPP framework than with C2H4. Systematic breakthrough experiments demonstrated outstanding separation performance for binary C2H6/C2H4 and C3H6/C2H4 mixtures, as well as ternary C3H6/C2H6/C2H4 mixtures, achieving record productivities of 150.2 and 86.5 L·kg-1 for polymer-grade C2H4 (≥99.9%) and C3H6 (≥99.5%), respectively. Notably, the separation performance remained stable under variable flow rates, temperatures, humidities, and multiple adsorption-desorption cycles. Overall, this study highlighted Al-TCPP as a highly competitive adsorbent for addressing the challenges in MTO product separation. Moreover, it offered valuable insights into the design of MOFs with heteroatom-rich accessible sites for efficient separation of low-carbon hydrocarbons.

Repairing Lattice Defects by an Orienting Strategy in a Porous Crystal: Boosting Inverse C2H6/C2H4 Separation

Defects are a common occurrence in various materials, making their repair a topic of widespread attention. However, the repair of atomic-scale lattice defects in porous crystals presents a substantial challenge. Herein, the repair of a linker-defective framework (NTU-70D) is presented through an orienting strategy to obtain a perfect framework (NTU-70P). Caused by steric hindrance from adjacent carboxylates of isonicotinic acid (INA), the lattice linker defect in NTU-70D is repaired by formic acid-assistant (pushed to the opposite direction by steric hindrance) installation of additional INAs in a defined direction, an unprecedented example in PCP chemistry. The resulting NTU-70P exhibits regular and smooth nano-channels that are adorned with more OINA sites, leading to a significant increase in C2H6 uptake (51.0 to 90.2 cm3 g-1) and C2H6/C2H4 selectivity (1.6 to 2.5), as evidenced by modeling calculations and in situ IR analysis. Furthermore, it demonstrates a notable ability to produce poly-grade C2H4 (with a record value of 46.4 mL g-1) from C2H6-containing mixtures. This work presents the first example of repaired porous crystals for boosted inverse C2H6/C2H4 separation, and the insights gained into the lattice repair offer avenues for the development of rich defective systems in practical applications.

Ultrastable Imidazole-linked Porous Organic Cages for Ammonia Capture and Detection

Here, we report the facile synthesis of imidazole-linked porous organic cages (IPOCs) via an in situ cyclization reaction protocol. Specifically, three IPOCs with [2+4] lantern-like structures and one with a [3+6] triangular prism structure were successfully prepared through condensation reactions between tetraformyl-functionalized calix[4]arene and bis(o-phenylenediamine) monomers in a single pot. Notably, these IPOCs exhibit high porosity, with Brunauer-Emmett-Teller (BET) specific surface areas reaching up to 1162 m2 g-1. Moreover, they demonstrate excellent chemical stability in both strong acidic and alkaline solutions. Furthermore, IPOC-2 and IPOC-4 display a remarkable NH3 capturing capability, with uptakes of up to 11.5 mmol g-1 at 1 bar and 298 K, surpassing most reported porous organic materials. Additionally, IPOC-1 exhibits highly efficient fluorescent quenching sensing of aqueous NH3, with a detection limit as low as 3.35×10-6 M. These findings strongly suggest the potential for widespread use of imidazole linkages in the development of robust functional porous organic cage materials for diverse applications.

Phenol[4]arenes: Excellent Macrocyclic Precursors for Constructing Chiral Porous Organic Cages

The development of new chiral building blocks for constructing complex chiral architectures, such as macrocycles and cages, is both crucial and challenging. Although concave-shaped calixarenes have been established as versatile building blocks for the synthesis of cage compounds, there are no reports on cages constructed from chiral calix[4]arene derivatives. Herein, we present a straightforward and effective method for gram-scale synthesis of a new member of chiral calix[4]arene macrocycle enantiomers, namely, phenol[4]arene (PC[4]A). As a proof of concept, we functionalized these enantiomers into tetraformylphenol[4]arene (PC[4]ACHO) derivatives via the Duff reaction to construct chiral porous organic cages (CPOCs) using polyamine synthons. Specifically, we employ two fluorescent amine synthons, bis(4-aminophenyl)phenylamine and tris(4-aminophenyl)amine, to assemble with PC[4]ACHO enantiomers, resulting in [2 + 4] lantern-shaped and [6 + 8] truncated octahedral CPOCs, respectively. These structures have been unambiguously characterized by single-crystal X-ray diffraction and circular dichroism (CD) spectroscopy. Notably, the [6 + 8] truncated CPOCs exhibit internal diameters of approximately 3.1 nm, a cavity volume of around 5300 Å3, and high specific surface areas of up to 1300 m2 g-1 after desolvation, making them among the largest CPOCs reported. Additionally, investigations into their chiral sensing performance demonstrate that these PC[4]A-based CPOCs enable the enantioselective recognition of amino acids and their derivatives. This work strongly suggests that PC[4]A can serve as an excellent building block for the rational design of chiral materials with practical applications.

Beyond symmetric self-assembly and effective molarity: unlocking functional enzyme mimics with robust organic cages

The bespoke environments in enzyme active sites can selectively accelerate chemical reactions by as much as 1019. Macromolecular and supramolecular chemists have been inspired to understand and mimic these accelerations and selectivities for applications in catalysis for sustainable synthesis. Over the past 60+ years, mimicry strategies have evolved with changing interests, understanding, and synthetic advances but, ubiquitously, research has focused on use of a molecular "cavity". The activities of different cavities vary with the subset of features available to a particular cavity type. Unsurprisingly, without synthetic access to mimics able to encompass more/all of the functional features of enzyme active sites, examples of cavity-catalyzed processes demonstrating enzyme-like rate accelerations remain rare. This perspective will briefly highlight some of the key advances in traditional cavity catalysis, by cavity type, in order to contextualize the recent development of robust organic cage catalysts, which can exploit stability, functionality, and reduced symmetry to enable promising catalytic modes.

Bioinspired "Intermolecular Pocket" in Soft Molecular Crystal of Porous Organic Cage Exhibiting Reversible Guest Recognition

Porous Organic Cages (POCs) have gathered a lot of attention in sorts of fields. Previous studies often focused on the functionalization of their intrinsic porosity, while the utilization of the extrinsic porosity has been seldom reported. To date, the rational construction of functionalized extrinsic porosity in POCs is a serious challenge, which still relies on trial and error. Inspired by hydrophobic proteins, in the contribution, a POC (namely NKPOC-DS) is obtained with hydrophobic "intermolecular pocket" as extrinsic porosity constructed through the assembly of disulfide bonds with hydrophobic groups, facilitating strong supramolecular interactions as confirmed by Electrostatic Potential (ESP) maps and single-crystal X-ray diffraction analysis. Notably, NKPOC-DS exhibits a unique C2H6-selective "breathing behaviour" due to the presence of softness in its extrinsic porosity, which does not extend to other gases such as C2H4, CH4, CO2, N2, and H2. Such specific recognition of C2H6 thus provides NKPOC-DS with the ability to preferentially adsorb C2H6 from a C2H6/C2H4 mixture. The innovative approach of biomimicry in the design of functional POCs provides new insights into manipulating the packing of cages, paving the way for potential applications in guest recognition and adsorption separations.

A Chemically Robust Microporous Zn-MOF for C2H2 Separation from CO2 and Industrially Relevant Four Component Gas Mixtures

The separation and purification of acetylene from the light hydrocarbon gas mixtures is considered as one of the most industrially challenging task for the production of fine chemicals. Though metal-organic frameworks (MOFs) are promising candidates for such separation and offer a cost and energy-efficient pathway, achieving the trade-off between sorption capacity and separation selectivity along with framework robustness is a daunting task and demands effective design. Herein, a new 3D chemically stable MOF, IITKGP-24 (stable over a wide range of aqueous pH solution, pH = 2-12) is developed, displaying excellent separation selectivity of 13.9 for C2H2/CO2 (50:50) even at ambient conditions and maintained a trade-off between sorption capacity and separation selectivity. Most importantly, the breakthrough performance analysis under the industrially relevant gas mixture composition revealed that the developed framework possesses excellent separation of acetylene from not only C2H2/CO2 (50:50) gas mixtures but also from the quaternary C2H2/C2H4/C2H6/CO2 (25:25:25:25) feed gas streams. Separation of C2H2 from such a four component gas mixture by MOFs is unexplored. The exceptional framework robustness, high C2H2/CO2 uptake ratio, low heat of adsorption, and excellent recyclability with easy regenerability made the developed framework promising candidate toward this challenging separation.

Tailored Postsynthetic Nitration of a Hypercrosslinked Polymer for Single-Step Ethylene Purification from a Ternary C2 Gas Mixture

Purifying C2H4 from a ternary C2H2/C2H4/C2H6 mixture poses a substantial industrial challenge due to their close physical and chemical properties. In this study, we introduce an innovative design approach to regulate and optimize the nitration degree of a hypercrosslinked polymer to achieve targeted separation performance. We synthesized a porous organic polymer (HCP) using the solvent knitting method and carried out its postsynthetic nitration, resulting in HCP-NO2-1 and HCP-NO2-2 with different nitration degrees. Notably, the adsorption capacity shifted from C2H6 > C2H4 ≈ C2H2 for HCP to C2H2 > C2H6 > C2H4 for HCP-NO2-1 and to C2H2 > C2H4 ≈ C2H6 for HCP-NO2-2, demonstrating the controllable nature of the separation process via the polar nitro group insertion. Remarkably, HCP-NO2-1 exhibited a desirable, selective separation of C2H4 from the C2H6/C2H4/C2H2 mixture thanks to an exquisite combination of the acidic proton-polar nitro group and nonpolar C-H⋅⋅⋅π interactions. Separation capability was further corroborated by computational simulations and breakthrough tests. This work marks a significant advancement as the first successful postsynthetic functionalization strategy for C2H4 purification from a ternary gas mixture among porous organic polymers.

Two amino-functionalized metal-organic frameworks with different topologies for C2H2/C2H4 separation

The rational design of metal-organic framework adsorbents is crucial for target gas separation. Herein, we report two three-dimensional MOFs with different topologies by regulating metal ions with amino-functionalized V-type ligands. Adsorption isotherms and Grand Canonical Monte Carlo simulation reveal that UPC-122 with channel-cavity structure has the potential to separate C2H2/C2H4 at room temperature with a separation ratio of 2.35 (50/50).

Stable Porous Organic Cage Nanocapsules for pH-Responsive Anticancer Drug Delivery for Precise Tumor Therapy

The search for drug nanocarriers with stimuli-responsive properties and high payloads for targeted drug delivery and precision medicine is currently a focal point of biomedical research, but this endeavor still encounters various challenges. Herein, a porous organic cage (POC) is applied to paclitaxel (PTX) drug delivery for cancer therapy for the first time. Specifically, water-soluble, stable, and biocompatible POC-based nanocapsules (PTX@POC@RH40) with PTX encapsulation efficiency over 98% can be synthesized by simply grafting nonionic surfactant (Polyoxyl 40 hydrogenated castor oil, RH40) on the POC surface. These PTX@POC@RH40 nanocapsules demonstrate remarkable stability for more than a week without aggregation and exhibit pH-responsive behavior under acidic conditions (pH 5.5) and display sustained release behavior at both pH 7.4 and pH 5.5. Intravenous administration of PTX@POC@RH40 led to a 3.5-fold increase in PTX bioavailability compared with the free PTX group in rats. Moreover, in vivo mouse model experiments involving 4T1 subcutaneous breast cancer tumors revealed that PTX@POC@RH40 exhibited enhanced anticancer efficacy with minimal toxicity compared with free PTX. These findings underscore the potential of POCs as promising nanocarriers for stimuli-responsive drug delivery in therapeutic applications.

Porous Organic Cage as an Efficient Platform for Industrial Radioactive Iodine Capture

Herein, we firstly develop porous organic cage (POC) as an efficient platform for highly effective radioactive iodine capture under industrial operating conditions (typically ≥150 °C), ≤150 ppmv of I2). Due to the highly dispersed and readily accessible binding sites as well as sufficient accommodating space, the constructed NKPOC-DT-(I-) (NKPOC=Nankai porous organic cage) demonstrates a record-high I2 uptake capacity of 48.35 wt % and extraordinary adsorption capacity of unit ionic site (~1.62) at 150 °C and 150 ppmv of I2. The I2 capacity is 3.5, 1.6, and 1.3 times higher than industrial silver-based adsorbents Ag@MOR and benchmark materials of TGDM and 4F-iCOF-TpBpy-I- under the same conditions. Furthermore, NKPOC-DT-(I-)Me exhibits remarkable adsorption kinetics (k1=0.013 min-1), which is 1.2 and 1.6 times higher than TGDM and 4F-iCOF-TpBpy-I- under the identical conditions. NKPOC-DT-(I-)Me thus sets a new benchmark for industrial radioactive I2 adsorbents. This work not only provides a new insight for effectively enhancing the adsorption capacity of unit functional sites, but also advances POC as an efficient platform for radioiodine capture in industry.

Recent advances in porous organic cages for energy applications

In recent years, the energy and environmental crises have attracted more and more attention. It is very important to develop new materials and technologies for energy storage and conversion. In particular, it is crucial to develop carriers that store energy or promote mass and electron transport. Emerging porous organic cages (POCs) are very suitable for this purpose because they have inherent advantages including structural designability, porosity, multifunction and post-synthetic modification. POC-based materials, such as pristine POCs, POC composites and POC derivatives also exhibit excellent energy-related properties. This latest perspective provides an overview of the progress of POC-based materials in energy storage and conversion applications, including photocatalysis, electrocatalysis (CO2RR, NO3RR, ORR, HER and OER), separation (gas separation and liquid separation), batteries (lithium-sulfur, lithium-ion and perovskite solar batteries) and proton conductivity, highlighting the unique advantages of POC-based materials in various forms. Finally, we summarize the current advances, challenges and further perspectives of POC-based materials in energy applications. This perspective will promote the design and synthesis of next-generation POC-based materials for energy applications.

Construction of stable porous organic cages: from the perspective of chemical bonds

Porous organic cages (POCs) are constructed from purely organic synthons by covalent linkages with intrinsic cavities and have shown potential applications in many areas. However, the majority of POC synthesis methods reported thus far have relied on dynamically reversible imine linkages, which can be metastable and unstable under humid or harsh chemical conditions. This instability significantly hampers their research prospects and practical applications. Consequently, strategies to enhance the chemical stability of POCs by modifying imine bonds and developing robust covalent linkages are imperative for realizing the full potential of these materials. In this review, we aim to highlight recent advancements in synthesizing chemical-stable POCs through these approaches and their associated applications. Additionally, we propose further strategies for creating stable POCs and discuss future opportunities for practical applications.

Correction: Recent applications of organic cages in sensing and separation processes in solution

Correction for 'Recent applications of organic cages in sensing and separation processes in solution' by Sonia La Cognata et al., Chem. Commun., 2023, 59, 13668-13678, https://doi.org/10.1039/D3CC04522F.

Crystalline Porous Organic Cage Membranes Constructed Using Fortified Intermolecular Interactions for Molecular Sieving

Among the various types of materials with intrinsic porosity, porous organic cages (POCs) are distinctive as discrete molecules that possess intrinsic cavities and extrinsic channels capable of facilitating molecular sieving. However, the fabrication of POC membranes remains highly challenging due to the weak noncovalent intermolecular interactions and most reported POCs are powders. In this study, we constructed crystalline free-standing porous organic cage membranes by fortifying intermolecular interactions through the induction of intramolecular hydrogen bonds, which was confirmed by single-crystal X-ray analysis. To elucidate the driving forces behind, a series of terephthaldehyde building blocks containing different substitutions were reacted with flexible triamine under different conditions via interfacial polymerization (IP). Furthermore, density functional theory (DFT) calculations suggest that intramolecular hydrogen bonding can significantly boost the intermolecular interactions. The resulting membranes exhibited fast solvent permeance and high rejection of dyes not only in water, but also in organic solvents. In addition, the membrane demonstrated excellent performance in precise molecular sieving in organic solvents. This work opens an avenue to designing and fabricating free-standing membranes composed of porous organic materials for efficient molecular sieving.

A Scalable Ultramicroporous Coordination Network for Ethylene Separation from the Quaternary Mixture

Adsorptive ethylene separation from the C2H2/C2H4/C2H6/CO2 four-component gas mixture provides a low-energy input solution for industrial ethylene purification, yet it is still a great challenge. Herein, we report a facile scaled-up synthesis of a stable ultramicroporous coordination network of Zn-CO3-datz (Hdatz = 3,5-diamine-1,2,4-triazole), which enables selective adsorption of C2H2, C2H4 and CO2 over C2H4, thanks to its specific pore environment supported by GCMC simulation of gas adsorption sites. Dynamic breakthrough experiments exhibited efficient one-step production of polymer-grade (≥99.95%) C2H4 from the quaternary C2H4/C2H2/C2H6/CO2 (1/1/1/1) mixture, with excellent C2H4 productivity of 0.12 mol kg-1 at 298 K. Moreover, it can be easily synthesized in kilogram scale with an affordable and low-cost ligand, rendering its further potential industrial applications.

De novo construction of amine-functionalized metal-organic cages as heterogenous catalysts for microflow catalysis

Microflow catalysis is a cutting-edge approach to advancing chemical synthesis and manufacturing, but the challenge lies in developing efficient and stable multiphase catalysts. Here we showcase incorporating amine-containing metal-organic cages into automated microfluidic reactors through covalent bonds, enabling highly continuous flow catalysis. Two Fe4L4 tetrahedral cages bearing four uncoordinated amines were designed and synthesized. Post-synthetic modifications of the amine groups with 3-isocyanatopropyltriethoxysilane, introducing silane chains immobilized on the inner walls of the microfluidic reactor. The immobilized cages prove highly efficient for the reaction of anthranilamide with aldehydes, showing superior reactivity and recyclability relative to free cages. This superiority arises from the large cavity, facilitating substrate accommodation and conversion, a high mass transfer rate and stable covalent bonds between cage and microreactor. This study exemplifies the synergy of cages with microreactor technology, highlighting the benefits of heterogenous cages and the potential for future automated synthesis processes.

Systemic regulation of binding sites in porous coordination polymers for ethylene purification from ternary C2 hydrocarbons

The global demand for poly-grade ethylene (C2H4) is increasing annually. However, the energy-saving purification of this gas remains a major challenge due to the similarity in molecular properties among the ternary C2 hydrocarbons. To address this challenge, we report an approach of systematic tuning of the pore environment with organic sites (from -COOH to -CF3, then to -CH3) in porous coordination polymers (PCPs), of which NTU-73-CH3 shows remarkable capability for the direct production of poly-grade C2H4 from ternary C2 hydrocarbons under ambient conditions. In comparison, the precursor structure of NTU-73-COOH is unable to purify C2H4, while NTU-73-CF3 shows minimal ability to harvest C2H4. This is because the changed binding sites in the NTU-73-series not only eliminate the channel obstruction caused by the formation of gas clusters, but also enhance the interaction with acetylene (C2H2) and ethane (C2H6), as validated by in situ crystallographic and Raman analysis. Our findings, in particular the systematic tuning of the pore environment and the efficient C2H4 purification by NTU-73-CH3, provide a blueprint for the creation of advanced porous families that can handle desired tasks.

Synthesis of Calix[4]arene-Based Porous Organic Cages and Their Gas Adsorption

Two crystalline large-sized porous organic cages (POCs) based on conical calix[4]arene (C4A) were designed and synthesized. The four-jaw C4A unit tends to follow the face-directed self-assembly law with the planar triangular building blocks such as tris(4-aminophenyl)amine (TAPA) or 1,3,5-tris(4-aminophenyl)benzene (TAPB) to generate a predictable cage with a stoichiometry of [6+8]. The formation of the large cages is confirmed through their relative molecular mass measured using MALDI-TOF/TOF spectra. The protonated molecular ion peaks of C4A-TAPA and C4A-TAPB were observed at m/z 5109.0 (calculated for C336H240O24N32: m/z 5109.7) and m/z 5594.2 (calculated for C384H264O24N24: m/z 5598.4). C4A-POCs exhibit I-type N2 adsorption-desorption isotherms with the BET surface areas of 1444.9 m2 ⋅ g-1 and 1014.6 m2 ⋅ g-1. The CO2 uptakes at 273 K are 62.1 cm3 ⋅ g-1 and 52.4 cm3 ⋅ g-1 at a pressure of 100 KPa. The saturated iodine vapor static uptakes at 348 K are 3.9 g ⋅ g-1 and 3.5 g ⋅ g-1. The adsorption capacity of C4A-TAPA for SO2 reaches to 124.4 cm3 ⋅ g-1 at 298 K and 1.3 bar. Additionally, the adsorption capacities of C4A-TAPA for C2H2, C2H4, and C2H6 were evaluated.

A high density nanopore 3-triangulene kagome lattice

Nanopore-containing two-dimensional materials have been explored for a wide range of applications including filtration, sensing, catalysis, energy storage and conversion. Triangulenes have recently been experimentally synthesized in a variety of sizes. In this regard, using these systems as building blocks, we theoretically examined 3-triangulene kagome crystals with inherent holes of ∼12 Å diameter and a greater density array of nanopores (≥1013 cm-2) compared to conventional 2D systems. The energetic, electronic, and transport properties of pristine and B/N-doped 3-triangulene kagome crystals were evaluated through a combination of density functional theory and non-equilibrium Green's function method. The simulated scanning tunneling microscopy images clearly capture electronic perturbation around the doped sites, which can be used to distinguish the pristine system from the doped systems. The viability of precisely controlling the band structure and transport properties by changing the type and concentration of doping atoms is demonstrated. The findings presented herein can potentially widen the applicability of these systems that combine unique electronic properties and intrinsically high-density pores, which can pave the way for the next generation of nanopore-based devices.

A Novel Homoconjugated Propellane Triimide: Synthesis, Structural Analyses, and Gas Separation

Rigid three-dimensional (3D) polycyclic propellanes have garnered interest due to their unique conformational spaces, which display great potential use in selectivity, separation and as models to study through-space electronic interactions. Herein we report the synthesis of a novel rigid propellane, trinaphtho[3.3.3]propellane triimide, which comprises three imide groups embedded on a trinaphtho[3.3.3]propellane. This propellane triimide exhibits large bathochromic shift, amplified molar absorptivity, enhanced fluorescence, and lower reduction potential when compared to the subunits. Computational and experimental studies reveal that the effective through-space π-orbitals interacting (homoconjugation) occurs between the subunits. Single-crystal XRD analysis reveals that the propellane triimide has a highly quasi-D3h symmetric skeleton and readily crystallizes into different superstructures by changing alkyl chains at the imide positions. In particular, the porous 3D superstructure with S-shaped channels is promising for taking up ethane (C2H6) with very good selectivity over ethylene (C2H4), which can purify C2H4 from C2H6/C2H4 in a single separation step. This work showcases a new class of rare 3D polycyclic propellane with intriguing electronic and supramolecular properties.

Scalable Synthesis of Robust MOF for Challenging Ethylene Purification and Propylene Recovery with Record Productivity

Ethylene (C2H4) purification and propylene (C3H6) recovery are highly relevant in polymer synthesis, yet developing physisorbents for these industrial separation faces the challenges of merging easy scalability, economic feasibility, high moisture stability with great separation efficiency. Herein, we reported a robust and scalable MOF (MAC-4) for simultaneous recovery of C3H6 and C2H4. Through creating nonpolar pores decorated by accessible N/O sites, MAC-4 displays top-tier uptakes and selectivities for C2H6 and C3H6 over C2H4 at ambient conditions. Molecular modelling combined with infrared spectroscopy revealed that C2H6 and C3H6 molecules were trapped in the framework with stronger contacts relative to C2H4. Breakthrough experiments demonstrated exceptional separation performance for binary C2H6/C2H4 and C3H6/C2H4 as well as ternary C3H6/C2H6/C2H4 mixtures, simultaneously affording record productivities of 27.4 and 36.2 L kg-1 for high-purity C2H4 (≥99.9 %) and C3H6 (≥99.5 %). MAC-4 was facilely prepared at deckgram-scale under reflux condition within 3 hours, making it as a smart MOF to address challenging gas separations.

Fine-tuning the pore environment of ultramicroporous three-dimensional covalent organic frameworks for efficient one-step ethylene purification

The construction of functional three-dimensional covalent organic frameworks (3D COFs) for gas separation, specifically for the efficient removal of ethane (C2H6) from ethylene (C2H4), is significant but challenging due to their similar physicochemical properties. In this study, we demonstrate fine-tuning the pore environment of ultramicroporous 3D COFs to achieve efficient one-step C2H4 purification. By choosing our previously reported 3D-TPB-COF-H as a reference material, we rationally design and synthesize an isostructural 3D COF (3D-TPP-COF) containing pyridine units. Impressively, compared with 3D-TPB-COF-H, 3D-TPP-COF exhibits both high C2H6 adsorption capacity (110.4 cm3 g-1 at 293 K and 1 bar) and good C2H6/C2H4 selectivity (1.8), due to the formation of additional C-H···N interactions between pyridine groups and C2H6. To our knowledge, this performance surpasses all other reported COFs and is even comparable to some benchmark porous materials. In addition, dynamic breakthrough experiments reveal that 3D-TPP-COF can be used as a robust absorbent to produce high-purity C2H4 directly from a C2H6/C2H4 mixture. This study provides important guidance for the rational design of 3D COFs for efficient gas separation.

Adsorptive Separation of Methylfuran and Dimethylfuran by a Robust Porous Organic Cage

As vital raw materials in the chemical industry, 2-methylfuran (MeF) and 2,5-dimethylfuran (DMeF) are commonly produced as mixtures. The selective separation of MeF and DMeF is crucial yet challenging, with significant industrial and economic implications. This study presents an energy-efficient separation technique using a robust calix[4]resorcinarene-based supramolecular porous organic cage (POC), CPOC-301, to effectively capture DMeF from an equimolar MeF/DMeF mixture within 2 h, yielding 95.3% purity. The exceptional separation efficiency stems from the superior structural stability of CPOC-301, maintaining its initial porous crystalline structure during separation. Calculations show that CPOC-301 forms more C-H···π hydrogen bonds with DMeF versus MeF, accounting for its DMeF selectivity. CPOC-301 can be easily regenerated via heat under a vacuum and reused for over five adsorption-desorption cycles without significant performance loss. This work introduces an approach to separate similar organic molecules effectively using POC materials.

Separation of benzene and toluene associated with vapochromic behaviors by hybrid[4]arene-based co-crystals

The combination of macrocyclic chemistry with co-crystal engineering has promoted the development of materials with vapochromic behaviors in supramolecular science. Herein, we develop a macrocycle co-crystal based on hybrid[4]arene and 1,2,4,5-tetracyanobenzene that is able to construct vapochromic materials. After the capture of benzene and toluene vapors, activated hybrid[4]arene-based co-crystal forms new structures, accompanied by color changes from brown to yellow. However, when hybrid[4]arene-based co-crystal captures cyclohexane and pyridine, neither structures nor colors change. Interestingly, hybrid[4]arene-based co-crystal can separate benzene from a benzene/cyclohexane equal-volume mixture and allow toluene to be removed from a toluene/ pyridine equal-volume mixture with purities reaching 100%. In addition, the process of adsorptive separation can be visually monitored. The selectivity of benzene from a benzene/cyclohexane equal-volume mixture and toluene from a toluene/ pyridine equal-volume mixture is attributed to the different changes in the charge-transfer interaction between hybrid[4]arene and 1,2,4,5-tetracyanobenzene when hybrid[4]arene-based co-crystal captures different vapors. Moreover, hybrid[4]arene-based co-crystal can be reused without losing selectivity and performance. This work constructs a vapochromic material for hydrocarbon separation.

Crystalline porous organic salts

Crystalline porous organic salts (CPOSs), formed by the self-assembly of organic acids and organic bases through ionic bonding, possess definite structures and permanent porosity and have rapidly emerged as an important class of porous organic materials in recent years. By rationally designing and controlling tectons, acidity/basicity (pKa), and topology, stable CPOSs with permanent porosity can be efficiently constructed. The characteristics of ionic bonds, charge-separated highly polar nano-confined channels, and permanent porosity endow CPOSs with unique physicochemical properties, offering extensive research opportunities for exploring their functionalities and application scenarios. In this review, we systematically summarize the latest progress in CPOS research, describe the synthetic strategies for synthesizing CPOSs, delineate their structural characteristics, and highlight the differences between CPOSs and hydrogen-bonded organic frameworks (HOFs). Furthermore, we provide an overview of the potential applications of CPOSs in areas such as negative linear compression (NLC), proton conduction, rapid transport of CO2, selective and rapid transport of K+ ions, atmospheric water harvesting (AWH), gas sorption, molecular rotors, fluorescence modulation, room-temperature phosphorescence (RTP) and catalysis. Finally, the challenges and future perspectives of CPOSs are presented.

Light-Triggered Enhancement of Fluorescence Efficiency in Organic Cages

The fluorescence efficiency of excited molecules can be enhanced by many external factors. Here, we showcase a surprising phenomenon whereby light is used as a gating source to increase the fluorescence efficiency of organic cages composed of biphenyl subunits. We show that the enhancement of fluorescence is not due to structural changes or ground-state events. Cryo-fluorescence measurements and kinetic studies suggest a restriction of the phenyl-based structures in the excited state, leading to increased fluorescence, which is also supported by time-resolved measurements. Through computational calculations, we propose that the planarization of the biphenyl units within the cages contributes to emission enhancement. This phenomenon offers insights into the design of optoelectronic structures with improved fluorescence properties.

A general large-scale synthesis approach for crystalline porous materials

Crystalline porous materials such as covalent organic frameworks (COFs), metal-organic frameworks (MOFs) and porous organic cages (POCs) have been widely applied in various fields with outstanding performances. However, the lack of general and effective methodology for large-scale production limits their further industrial applications. In this work, we developed a general approach comprising high pressure homogenization (HPH), which can realize large-scale synthesis of crystalline porous materials including COFs, MOFs, and POCs under benign conditions. This universal strategy, as illustrated in the proof of principle studies, has prepared 4 COFs, 4 MOFs, and 2 POCs. It can circumvent some drawbacks of existing approaches including low yield, high energy consumption, low efficiency, weak mass/thermal transfer, tedious procedures, poor reproducibility, and high cost. On the basis of this approach, an industrial homogenizer can produce 0.96 ~ 580.48 ton of high-performance COFs, MOFs, and POCs per day, which is unachievable via other methods.

Construction of Negative Electrostatic Pore Environments in a Scalable, Stable and Low-Cost Metal-organic Framework for One-Step Ethylene Purification from Ternary Mixtures

One-step separation of C2 H4 from ternary C2 mixtures by physisorbents remains a challenge to combine excellent separation performance with high stability, low cost, and easy scalability for industrial applications. Herein, we report a strategy of constructing negative electrostatic pore environments in a stable, low-cost, and easily scaled-up aluminum MOF (MOF-303) for efficient one-step C2 H2 /C2 H6 /C2 H4 separation. This material exhibits not only record high C2 H2 and C2 H6 uptakes, but also top-tier C2 H2 /C2 H4 and C2 H6 /C2 H4 selectivities at ambient conditions. Theoretical calculations combined with in situ infrared spectroscopy indicate that multiple N/O sites on pore channels can build a negative electro-environment to provide stronger interactions with C2 H2 and C2 H6 over C2 H4 . Breakthrough experiments confirm its exceptional separation performance for ternary mixtures, affording one of the highest C2 H4 productivity of 1.35 mmol g-1 . This material is highly stable and can be easily synthesized at kilogram-scale from cheap raw materials using a water-based green synthesis. The benchmark combination of excellent separation properties with high stability and low cost in scalable MOF-303 has unlocked its great potential in this challenging industrial separation.

Kilogram-Scale Fabrication of a Robust Olefin-Linked Covalent Organic Framework for Separating Ethylene from a Ternary C2 Hydrocarbon Mixture

One-step adsorptive purification of ethylene (C2H4) from a ternary mixture of acetylene (C2H2), C2H4, and ethane (C2H6) by a single material is of great importance but challenging in the petrochemical industry. Herein, a chemically robust olefin-linked covalent organic framework (COF), NKCOF-62, is designed and synthesized by a melt polymerization method employing tetramethylpyrazine and terephthalaldehyde as cheap monomers. This method avoids most of the disadvantages of classical solvothermal methods, which enable the cost-effective kilogram fabrication of olefin-linked COFs in one pot. Furthermore, NKCOF-62 shows remarkably selective adsorption of C2H2 and C2H6 over C2H4 thanks to its unique pore environments and suitable pore size. Breakthrough experiments demonstrate that polymer-grade C2H4 can be directly obtained from C2H2/C2H6/C2H4 (1/1/1) ternary mixtures through a single separation process. Notably, NKCOF-62 is the first demonstration of the potential to use COFs for C2H2/C2H6/C2H4 separation, which provides a blueprint for the design and construction of robust COFs for industrial gas separations.

Incorporation of multiple supramolecular binding sites into a robust MOF for benchmark one-step ethylene purification

One-step adsorption separation of C2H4 from ternary C2 hydrocarbon mixtures remains an important and challenging goal for petrochemical industry. Current physisorbents either suffer from unsatisfied separation performance, poor stability, or are difficult to scale up. Herein, we report a strategy of constructing multiple supramolecular binding sites in a robust and scalable MOF (Al-PyDC) for highly efficient one-step C2H4 purification from ternary mixtures. Owing to suitable pore confinement with multiple supramolecular binding sites, Al-PyDC exhibits one of the highest C2H2 and C2H6 uptakes and selectivities over C2H4 at ambient conditions. The gas binding sites have been visualized by single-crystal X-ray diffraction studies, unveiling that the low-polarity pore surfaces with abundant electronegative N/O sites provide stronger multiple supramolecular interactions with C2H2 and C2H6 over C2H4. Breakthrough experiments showed that polymer-grade C2H4 can be separated from ternary mixtures with a maximum productivity of 1.61 mmol g-1. This material can be prepared from two simple reagents using a green synthesis method with water as the sole solvent, and its synthesis can be easily scaled to multikilogram batches. Al-PyDC achieves an effective combination of benchmark separation performance, high stability/recyclability, green synthesis and easy scalability to address major challenges for industrial one-step C2H4 purification.

Aminal-Linked Covalent Organic Frameworks with hxl-a and Quasi-hcb Topologies for Efficient C2 H6 /C2 H4 Separation

In reticular chemistry, topology is a powerful concept for defining the structures of covalent organic frameworks (COFs). However, due to the lack of diversity in the symmetry and reaction stoichiometry of the monomers, only 5% of the two-dimensional topologies have been reported to be COFs. To overcome the limitations of COF connectivity and pursue novel topologies in COF structures, two aminal-linked COFs, KUF-2 and KUF-3, are prepared, with dumbbell-shaped secondary building units. Linear dialdehydes and piperazine are condensed at a ratio of 1:2 to construct an aminal linkage, leading to unreported hxl-a (KUF-2) and quasi-hcb (KUF-3) structures. Notably, KUF-3 displays top-tier C2 H6 /C2 H4 selectivity and C2 H6 uptake at 298 K, outperforming most porous organic materials. The intrinsic aromatic ring-rich and Lewis basic pore environments, and appropriate pore widths enable the selective adsorption of C2 H6 , as confirmed by Grand Canonical Monte Carlo simulations. Dynamic breakthrough curves revealed that C2 H6 can be selectively separated from a gas mixture of C2 H6 and C2 H4 . This study suggests that topology-based design of aminal-COFs is an effective strategy for expanding the field of reticular chemistry and provides the facile integration of strong Lewis basic sites for selective C2 H6 /C2 H4 separation.

Polycage membranes for precise molecular separation and catalysis

The evolution of the chemical and pharmaceutical industry requires effective and less energy-intensive separation technologies. Engineering smart materials at a large scale with tunable properties for molecular separation is a challenging step to materialize this goal. Herein, we report thin film composite membranes prepared by the interfacial polymerization of porous organic cages (POCs) (RCC3 and tren cages). Ultrathin crosslinked polycage selective layers (thickness as low as 9.5 nm) are obtained with high permeance and strict molecular sieving for nanofiltration. A dual function is achieved by combining molecular separation and catalysis. This is demonstrated by impregnating the cages with highly catalytically active Pd nanoclusters ( ~ 0.7 nm). While the membrane promotes a precise molecular separation, its catalytic activity enables surface self-cleaning, by reacting with any potentially adsorbed dye and recovering the original performance. This strategy opens opportunities for the development of other smart membranes combining different functions and well-tailored abilities.

Preparation of Chiral Porous Organic Cage Clicked Chiral Stationary Phase for HPLC Enantioseparation

Porous organic cages (POCs) are a new subclass of porous materials, which are constructed from discrete cage molecules with permanent cavities via weak intermolecular forces. In this study, a novel chiral stationary phase (CSP) has been prepared by chemically binding a [4 + 6]-type chiral POC (C120H96N12O4) with thiol-functionalized silica gel using a thiol-ene click reaction and applied to HPLC separations. The column packed with this CSP presented good separation capability for chiral compounds and positional isomers. Thirteen racemates have been enantioseparated on this column, including alcohols, diols, ketones, amines, epoxides, and organic acids. Upon comparison with a previously reported chiral POC NC1-R-based column, commercial Chiralpak AD-H, and Chiralcel OD-H columns, this column is complementary to these three columns in terms of its enantiomeric separation; and can also separate some racemic compounds that cannot be separated by the three columns. In addition, eight positional isomers (iodoaniline, bromoaniline, chloroaniline, dibromobenzene, dichlorobenzene, toluidine, nitrobromobenzene, and nitroaniline) have also been separated. The influences of the injection weight and column temperature on separation have been explored. After the column has undergone multiple injections, the relative standard deviations (RSDs) for the retention time and selectivity were below 1.0 and 1.5%, respectively, indicating the good reproducibility and stability of the column for separation. This work demonstrates that POCs are promising materials for HPLC separation.

Highly Connected Three-Dimensional Covalent Organic Framework with Flu Topology for High-Performance Li-S Batteries

Lithium-sulfur batteries (LSBs) have been considered as a promising candidate for next-generation energy storage devices, which however still suffer from the shuttle effect of the intermediate lithium polysulfides (LiPSs). Covalent-organic frameworks (COFs) have exhibited great potential as sulfur hosts for LSBs to solve such a problem. Herein, a pentiptycene-based D_2h symmetrical octatopic polyaldehyde, 6,13-dimethoxy-2,3,9,10,18,19,24,25-octa(4'-formylphenyl)pentiptycene (DMOPTP), was prepared and utilized as a building block toward preparing COFs. Condensation of DMOPTP with 4-connected tetrakis(4-aminophenyl)methane affords an expanded [8 + 4] connected network 3D-flu-COF, with a flu topology. The non-interpenetrated nature of the flu topology endows 3D-flu-COF with a high Brunauer-Emmett-Teller surface area of 2860 m² g^-1, large octahedral cavities, and cross-linked tunnels in the framework, enabling a high loading capacity of sulfur (∼70 wt %), strong LiPS adsorption capability, and facile ion diffusion. Remarkably, when used as a sulfur host for LSBs, 3D-flu-COF delivers a high capacity of 1249 mA h g^-1 at 0.2 C (1.0 C = 1675 mA g^-1), outstanding rate capability (764 mA h g^-1 at 5.0 C), and excellent stability, representing one of the best results among the thus far reported COF-based sulfur host materials for LSBs and being competitive with the state-of-the-art inorganic host materials.

Fe-MOF with U-Shaped Channels for C2H2/CO2 and C2H2/C2H4 Separation

The development of high-performance adsorbents is critical for the low-energy separation of acetylene. Herein, we synthesized an Fe-MOF (MOF, metal-organic framework) with U-shaped channels. The adsorption isotherms of C₂H₂, C₂H₄, and CO₂ show that the adsorption capacity of acetylene is significantly larger than that of the other two gases. Meanwhile, the actual separation performance was verified by breakthrough experiments, indicating the potential to separate C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures at normal temperatures. Grand Canonical Monte Carlo (GCMC) simulation demonstrates that the framework with U-shaped channels interacts more strongly with C₂H₂ than with C₂H₄ and CO₂. The high C₂H₂ uptake and low adsorption enthalpy highlight Fe-MOF as a promising candidate for C₂H₂/CO₂ separation with a low regeneration energy.

Insights into the Absorption of Hydrocarbon Gases in Phosphorus-Containing Ionic Liquids

The solubility of ethane, ethylene, propane, and propylene was measured in two phosphorus-containing ionic liquids, trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate, [P_6,6,6,14][DiOP], and 1-butyl-3-methylimidazolium dimethylphosphate, [C₄C₁Im][DMP], using an isochoric saturation method. The ionic liquid [C₄C₁Im][DMP] absorbed between 1 and 20 molecules of gas per 1000 ion pairs, at 313 K and 0.1 MPa, while [P_6,6,6,14][DiOP] absorbed up to 169 molecules of propane per 1000 ion pairs under the same conditions. [C₄C₁Im][DMP] had a higher capacity to absorb olefins than paraffins, while the opposite was true for [P_6,6,6,14][DiOP], with the former being slightly more selective than the later. From the analysis of the thermodynamic properties of solvation, we concluded that in both ionic liquids and for all of the studied gases the solvation is ruled by the entropy, even if its contribution is unfavorable. These results, together with density measurements, 2D NMR studies, and self-diffusion coefficients suggest that the gases' solubility is ruled mostly by nonspecific interactions with the ionic liquids and that the looser ion packing in [P_6,6,6,14][DiOP] makes it easier to accommodate the gases compared to [C₄C₁Im][DMP].

Highly Robust Microporous Metal-Organic Frameworks for Efficient Ethylene Purification under Dry and Humid Conditions

Two C₂ H₆ -selective metal-organic framework (MOF) adsorbents with ultrahigh stability, high surface areas, and suitable pore size have been designed and synthesized for one-step separation of ethane/ethylene (C₂ H₆ /C₂ H₄ ) under humid conditions to produce polymer-grade pure C₂ H₄ . Experimental results reveal that these two MOFs not only adsorb a high amount of C₂ H₆ but also display good C₂ H₆ /C₂ H₄ selectivity verified by fixed bed column breakthrough experiments. Most importantly, the good water stability and hydrophobic pore environments make these two MOFs capable of efficiently separating C₂ H₆ /C₂ H₄ under humid conditions, exhibiting the benchmark performance among all reported adsorbents for separation of C₂ H₆ /C₂ H₄ under humid conditions. Moreover, the affinity sites and their static adsorption energies were successfully revealed by single crystal data and computation studies. Adsorbents described in this work can be used to address major chemical industrial challenges.

Preparation and evaluation of a chiral porous organic cage based chiral stationary phase for enantioseparation in high performance liquid chromatography

Porous organic cages (POCs) are a new kind of porous molecular materials, which have gained widespread interest in many fields due to their intriguing properties, including excellent molecular solubility, inherent molecular cavity and rich host-guest chemistry. To date, many chiral POCs have been explored as chiral stationary phases (CSPs) for gas chromatographic (GC) separation of enantiomers. However, the applications of chiral POCs for high performance liquid chromatography (HPLC) enantiomeric separation is extremely rare. In this study, we report the construction of thiol-ene click reaction for the preparation of CSP for HPLC by using a [4+8]-type chiral POC NC4-R as chiral selector. The fabricated CSP showed good chiral resolution performance not only in normal-phase HPLC (NP-HPLC) but also in reversed-phase HPLC (RP-HPLC). Seventeen and ten racemates were well resolved in the two separation modes, respectively, including ketones, esters, alcohols, phenols, amines, ethers, organic acids, and amino acids. Moreover, the fabricated column also shows good chiral recognition complementarity to two popular chiral HPLC columns (Chiralpak AD-H and Chiralcel OD-H columns) and previously reported chiral POC NC1-R-based HPLC column, which can resolve some racemates that unable to be resolved by the two commercially available chiral HPLC columns and NC1-R-based column. The relative standard deviation (RSD) values (n = 4) of retention time and resolution (Rs) of analytes separated on the column were less than 0.3 % and 0.5 % after it was subjected to different injections, showing the good reproducibility and stability of the NC4-R-based column. This work demonstrated high potentials of chiral POCs for HPLC enantioseparation and the applicability of chiral POC-based HPLC columns can be broadened by developing more chiral POCs with diverse structures as chiral selector for HPLC.

One-Step Ethylene Purification from Ternary Mixtures in a Metal-Organic Framework with Customized Pore Chemistry and Shape

Adsorptive separation is an energy-efficient technology for the separation of C2 hydrocarbons. However, it remains a critical problem to directly produce high-purity C₂ H₄ from ternary C₂ H₂ /C₂ H₄ /C₂ H₆ mixtures by simultaneously trapping C₂ H₂ and C₂ H₆ . Herein, we report the one-step C₂ H₄ purification from the ternary mixture by a metal-organic framework Zn(ad)(int) (ad=adeninate; int=isonicotinate). The material combines dense heterocyclic rings and accessible uncoordinated O atoms as strong binding sites for C₂ H₆ and C₂ H₂ . Its spindle-like cage exhibits an interesting shape matching with the targeted molecules, affording Zn(ad)(int) not only high separation selectivity for C₂ H₆ /C₂ H₄ and C₂ H₂ /C₂ H₄ , but also excellent gas capacity. Breakthrough experiments show that polymer-grade C₂ H₄ can be separated from the ternary mixtures with a record productivity of 1.43 mmol g^-1 . In situ powder X-ray diffraction and Fourier transform infrared spectrum analyses further provide deep insights into the separation mechanism.

Purely Covalent Molecular Cages and Containers for Guest Encapsulation

Cage compounds offer unique binding pockets similar to enzyme-binding sites, which can be customized in terms of size, shape, and functional groups to point toward the cavity and many other parameters. Different synthetic strategies have been developed to create a toolkit of methods that allow preparing tailor-made organic cages for a number of distinct applications, such as gas separation, molecular recognition, molecular encapsulation, hosts for catalysis, etc. These examples show the versatility and high selectivity that can be achieved using cages, which is impossible by employing other molecular systems. This review explores the progress made in the field of fully organic molecular cages and containers by focusing on the properties of the cavity and their application to encapsulate guests.

Ultramicroporous material based parallel and extended paraffin nano-trap for benchmark olefin purification

Selective paraffin capture from olefin/paraffin mixtures could afford high-purity olefins directly, but suffers from the issues of low separation selectivity and olefin productivity. Herein, we report an ultramicroporous material (PCP-IPA) with parallel-aligned linearly extending isophthalic acid units along the one-dimensional channel, realizing the efficient production of ultra-high purity C₂H₄ and C₃H₆ (99.99%). The periodically expanded and parallel-aligned aromatic-based units served as a paraffin nano-trap to contact with the exposed hydrogen atoms of both C₂H₆ and C₃H₈, as demonstrated by the simulation studies. PCP-IPA exhibits record separation selectivity of 2.48 and separation potential of 1.20 mol/L for C₃H₈/C₃H₆ (50/50) mixture, meanwhile the excellent C₂H₆/C₂H₄ mixture separation performance. Ultra-high purity C₃H₆ (99.99%) and C₂H₄ (99.99%) can be directly obtained through fixed-bed column from C₃H₈/C₃H₆ and C₂H₆/C₂H₄ mixtures, respectively. The record C₃H₆ productivity is up to 15.23 L/kg from the equimolar of C₃H₈/C₃H₆, which is 3.85 times of the previous benchmark material, demonstrating its great potential for those important industrial separations.