Transforming Porous Organic Cages into Porous Ionic Liquids via a Supramolecular Complexation Strategy.

Porous liquids are a type of porous materials that engineer permanent porosity into unique flowing liquids, exhibiting promising functionalities for a variety of applications. Here a Type I porous liquid is synthesized by transforming porous organic cages into porous ionic liquids via a supramolecular complexation strategy. Simple physical mixing of 18-crown-6 with task-specific anionic porous organic cages affords a porous ionic liquid with anionic porous organic cages as the anionic parts and 18-crown-6/potassium ion complexes as the cationic parts. In contrast, mixing of 15-crown-5 and anionic porous organic cages in a 2:1 ratio gives only solids, while the addition of excess 15-crown-5 affords a Type II porous liquid. The permanent porosity in the cage-based porous liquids has been also confirmed by molecular simulation, positron (e+ ) annihilation lifetime spectroscopy, and enhanced gas sorption capacity compared with pure crown ethers.

Porous liquid zeolites: hydrogen bonding-stabilized H-ZSM-5 in branched ionic liquids.

Porous liquids, as a newly emerging type of porous material, have great potential in gas separation and storage. However, the examples and synthetic strategies reported so far likely represent only the tip of the iceberg due to the great difficulty and challenge in engineering permanent porosity in liquid matrices. Here, by taking advantage of the hydrogen bonding interaction between the alkane chains of branched ionic liquids and the Brønsted sites in H-form zeolites, as well as the mechanical bond of the long alkyl chain of the cation penetrated into the zeolite channel at the interface, the H-form zeolites can be uniformly stabilized in branched ionic liquids to form porous liquid zeolites, which not only significantly improve their gas sorption performance, but also change the gas sorption-desorption behavior because of the preserved permanent porosity. Furthermore, such a facile synthetic strategy can be extended to fabricate other types of H-form zeolite-based porous liquids by taking advantage of the tunability of the counter-anion (e.g., NTf2-, BF4-, EtSO4-, etc.) in branched ionic liquids, thus opening up new opportunities for porous liquids for specific applications in energy and environment.

Guanidinium-Based Ionic Covalent Organic Framework for Rapid and Selective Removal of Toxic Cr(VI) Oxoanions from Water.

Ionic covalent organic frameworks make up an emerging class of functional materials in which the included ionic interfaces induce strong and attractive interactions with ionic species of the opposite charge. In this work, the strong and selective binding forces between the confined diiminoguanidinium groups in the framework and tetrahedral oxoanions have led to unparalleled effectiveness in the removal of the toxic chromium(VI) pollutant from aqueous solutions. The new functional framework can take up from 90 to 200 mg/g of chromium(VI), depending on the solution pH, and is capable of decreasing the chromium(VI) concentration in water from 1 ppm to 10 ppb within minutes (an order of magnitude below the current U.S. Environmental Protection Agency maximum contaminant level of 100 ppb), demonstrating superior properties among known ion exchange materials and natural sorbents.

Prediction of Carbon Dioxide Adsorption via Deep Learning.

Porous carbons with different textural properties exhibit great differences in CO2 adsorption capacity. It is generally known that narrow micropores contribute to higher CO2 adsorption capacity. However, it is still unclear what role each variable in the textural properties plays in CO2 adsorption. Herein, a deep neural network is trained as a generative model to direct the relationship between CO2 adsorption of porous carbons and corresponding textural properties. The trained neural network is further employed as an implicit model to estimate its ability to predict the CO2 adsorption capacity of unknown porous carbons. Interestingly, the practical CO2 adsorption amounts are in good agreement with predicted values using surface area, micropore and mesopore volumes as the input values simultaneously. This unprecedented deep learning neural network (DNN) approach, a type of machine learning algorithm, exhibits great potential to predict gas adsorption and guide the development of next-generation carbons.

New Class of Type III Porous Liquids: A Promising Platform for Rational Adjustment of Gas Sorption Behavior.

Porous materials have already manifested their unique properties in a number of fields. Generally, all porous materials are in a solid state other than liquid, in which molecules are closely packed without porosity. "Porous" and "liquid" seem like antonyms. Herein, we report a new class of Type 3 porous liquids based on rational coupling of microporous framework nanoparticles as porous hosts with a bulky ionic liquid as the fluid media. Positron annihilation lifetime spectroscopy (PALS) and CO2 adsorption measurements confirm the successful engineering of permanent porosity into these liquids. Compared to common porous solid materials, as-synthesized porous liquids exhibited pronounced hysteresis loops in the CO2 sorption isotherms even at ambient conditions (298 K, 1 bar). The unique features of these novel porous liquids could bring new opportunities in many fields including gas separation and storage, air separation and regeneration, gas transport, and permanent gas storage at ambient conditions.

Electrostatic-Assisted Liquefaction of Porous Carbons.

Porous liquids are a newly developed porous material that combine unique fluidity with permanent porosity, which exhibit promising functionalities for a variety of applications. However, the apparent incompatibility between fluidity and permanent porosity makes the stabilization of porous nanoparticle with still empty pores in the dense liquid phase a significant challenging. Herein, by exploiting the electrostatic interaction between carbon networks and polymerized ionic liquids, we demonstrate that carbon-based porous nanoarchitectures can be well stabilized in liquids to afford permanent porosity, and thus opens up a new approach to prepare porous carbon liquids. Furthermore, we hope this facile synthesis strategy can be widely applicated to fabricate other types of porous liquids, such as those (e.g., carbon nitride, boron nitride, metal-organic frameworks, covalent organic frameworks etc.) also having the electrostatic interaction with polymerized ionic liquids, evidently advancing the development and understanding of porous liquids.

Solid-state synthesis of ordered mesoporous carbon catalysts via a mechanochemical assembly through coordination cross-linking.

Ordered mesoporous carbons (OMCs) have demonstrated great potential in catalysis, and as supercapacitors and adsorbents. Since the introduction of the organic-organic self-assembly approach in 2004/2005 until now, the direct synthesis of OMCs is still limited to the wet processing of phenol-formaldehyde polycondensation, which involves soluble toxic precursors, and acid or alkali catalysts, and requires multiple synthesis steps, thus restricting the widespread application of OMCs. Herein, we report a simple, general, scalable and sustainable solid-state synthesis of OMCs and nickel OMCs with uniform and tunable mesopores (∼4-10 nm), large pore volumes (up to 0.96 cm3 g-1) and high-surface areas exceeding 1,000 m2 g-1, based on a mechanochemical assembly between polyphenol-metal complexes and triblock co-polymers. Nickel nanoparticles (∼5.40 nm) confined in the cylindrical nanochannels show great thermal stability at 600 °C. Moreover, the nickel OMCs offer exceptional activity in the hydrogenation of bulky molecules (∼2 nm).