Preserving Mesoporosity in Type III Porous Liquids through Dual-layer Surface Weaving

The fundamental limitation for pore preservation in a Type III porous liquid (T3PL) is the need for a small aperture from the porous filler to realize size exclusion of a bulky solvent. We present a dual-layer surface weaving strategy that can disregard this limitation and achieve micro- and mesoporous metal-organic framework (MOF)-based T3PLs even with apertures much larger than the solvent molecules. By first weaving a tight network of poly(tert-butyl methacrylate) on the MOF surface, the poly(dimethylsiloxane) (PDMS) solvent can be effectively excluded from the pores while smaller guest molecules such as CO2, C2H4, and H2O can freely access the interior, as confirmed by low-pressure adsorption isotherms. Further application of a PDMS-containing polymer coating helps lower the viscosity of the PL due to increased particle dispersibility. This strategy has resulted in the successful construction of T3PLs with aperture sizes up to 3.1 nm.

Effects of Particle Size on the Gas Uptake Kinetics and Physical Properties of Type III Porous Liquids

Type III porous liquids (PLs) consist of porous solid particles dispersed in a size-excluded liquid phase and are attracting much attention as novel media for applications such as gas separation. However, the effects of fundamental variables such as particle size on their physical properties are currently largely unknown. Here we study the effects of particle size in a series of porous liquids based on solid Al(OH)(fumarate) (a microporous metal-organic framework, MOF) with particle sizes of 60 nm, 200-600 nm, or 800-1000 dispersed in liquid polydimethylsiloxane (PDMS). Properties examined include physical stability of the dispersion, viscosity, total CO2 uptake, and kinetics of CO2 uptake. As expected, both physical stability and viscosity decreased with increasing particle size. Unexpectedly, total gravimetric gas uptake also varied with particle size, being greatest for the largest particles, which we ascribe to larger particles having a lower relative content of surface-bound FMA ligands. Various models for the gas uptake kinetic data were considered, specifically adsorption reaction models such as pseudo-first-order, pseudo-second-order, and Elovich models. In contrast to pure PDMS, which showed first-order kinetics, all PLs fit best to the Elovich model confirming that their uptake mechanism is more complex than for a simple liquid. Adsorption diffusion models, specifically Weber and Morris' intraparticle model and Boyd's model, were also applied which revealed a three-step process in which a combination of diffusion through a surface layer and intraparticle diffusion were rate-limiting. The rate of gas uptake follows the order PDMS < PL1 < PL2 < PL3, showing that the porous liquids take up gas more rapidly than does PDMS and that this rate increases with particle size. Overall, the study suggests that for high gas uptake and fast uptake kinetics, large particles may be preferred. Also, the fact that large particles resulted in low viscosity may be advantageous in reducing the pumping energy needed in flow separation systems. Therefore, the work suggests that finding ways to stabilize PLs with large particles against phase separation could be advantageous for optimizing the properties of PLs toward applications.

Slippery Porous-Liquid-Infused Porous Surface (SPIPS) with On-Demand Responsive Switching between "Defensive" and "Offensive" Antifouling Modes

Slippery liquid-infused porous surfaces (SLIPS) have received widespread attention in the antifouling field. However, the reduction in antifouling performance caused by lubricant loss limits their application in marine antifouling. Herein, inspired by the skin of a poison dart frog which contains venom glands and mucus, a porous liquid (PL) based on ZIF-8 is prepared as a lubricant and injected into a silicone polyurethane (SPU) matrix to construct a new type of SLIPS for marine antifouling applications: the slippery porous-liquid-infused porous surface (SPIPS). The SPIPS consists of a responsive antifoulant-releasing switch between "defensive" and "offensive" antifouling modes to intelligently enhance the antifouling effect after lubricant loss. The SPIPS can adjust antifouling performance to meet the antifouling requirements under different light conditions. The wastage of antifoulants is reduced, thereby effectively maintaining the durability and service life of SLIPS materials. The SPIPS exhibits efficient lubricant self-replenishment, self-cleaning, anti-protein, anti-bacterial, anti-algal, and self-healing (97.48%) properties. Furthermore, it shows satisfactory 360-day antifouling performance in actual marine fields during boom seasons, demonstrating the longest antifouling lifespan in the field tests of reported SLIPS coatings. Hence, the SPIPS can effectively promote the development of SLIPS for neritic antifouling.

Molecular Simulation of SO2 Separation and Storage Using a Cryptophane-Based Porous Liquid

A theoretical molecular simulation study of the encapsulation of gaseous SO2 at different temperature conditions in a type II porous liquid is presented here. The system is composed of cage cryptophane-111 molecules that are dispersed in dichloromethane, and it is described using an atomistic modelling of molecular dynamics. Gaseous SO2 tended to almost fully occupy cryptophane-111 cavities throughout the simulation. Calculations were performed at 300 K and 283 K, and some insights into the different adsorption found in each case were obtained. Simulations with different system sizes were also studied. An experimental-like approach was also employed by inserting a SO2 bubble in the simulation box. Finally, an evaluation of the radial distribution function of cryptophane-111 and gaseous SO2 was also performed. From the results obtained, the feasibility of a renewable separation and storage method for SO2 using porous liquids is mentioned.

Molecular Simulation of CO2 and H2 Encapsulation in a Nanoscale Porous Liquid

In this study we analyse from a theoretical perspective the encapsulation of both gaseous H2 and CO2 at different conditions of pressure and temperature in a Type II porous liquid, composed by nanometric scale cryptophane-111 molecules dispersed in dichloromethane, using atomistic molecular dynamics. Gaseous H2 tends to occupy cryptophane-111's cavities in the early stages of the simulation; however, a remarkably greater selectivity of CO2 adsorption can be seen in the course of the simulation. Calculations were performed at ambient conditions first, and then varying temperature and pressure, obtaining some insight about the different adsorption found in each case. An evaluation of the host molecule cavities accessible volume was also performed, based on the guest that occupies the pore. Finally, a discussion between the different intermolecular host-guest interactions is presented, justifying the different selectivity obtained in the molecular simulation calculations. From the results obtained, the feasibility of a renewable separation and storage method for CO2 using these nanometric scale porous liquids is pointed out.

Cyclodextrin Porous Liquid Materials for Efficient Chiral Recognition and Separation of Nucleosides

Porous liquids are porous materials that have exhibited unique properties in various fields. Herein, we developed a method to synthesize the type I porous liquids via liquefaction of cyclodextrins by chemical modification. The cyclodextrin porous liquids were characterized by Fourier-transform infrared (FTIR) spectroscopy, NMR, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS), circular dichroism (CD), and UV-vis spectroscopy. The measured ionic conductivity of the γ-cyclodextrin porous liquid was 500 times as great as that of its reactants, which was found to be the first instance with such great conductivity for a type I porous liquid. What is more, the γ-cyclodextrin porous liquid had been demonstrated experimentally to have outstanding chiral recognition ability toward pyrimidine nucleosides in water, which was further confirmed by computational simulations. Additionally, enantiomeric excess of the extracted nucleoside was achieved up to 84.81% by convenient extraction from the mixture of racemic nucleosides and γ-cyclodextrin porous liquid. The great features of the novel cyclodextrin porous liquids could bring opportunities in many fields, including the preparation of chiral separation materials, development of new drug screening mechanisms, and construction of chiral response materials.

Facilitate Gas Transport through Metal-Organic Polyhedra Constructed Porous Liquid Membrane

Type II porous liquids are demonstrated to be promise porous materials. However, the category of porous hosts is very limited. Here, a porous host metal-organic polyhedra (MOP-18) is reported to construct type II porous liquids. MOP-18 is dissolved into 15-crown-5 as an individual cage (5 nm). Both the molecular dynamics simulations and experimental gravimetric CO₂ solubility test indicate that the inner cavity of MOP-18 in porous liquids is unoccupied by 15-crown-5 and is accessible to CO₂ . Thus, the prepared porous liquids show enhanced gas solubility. Furthermore, the prepared porous liquid is encapsulated into graphene oxide (GO) nanoslits to form a GO-supported porous liquid membrane (GO-SPLM). Owing to the empty cavity of MOP-18 unit cages in porous liquids that reduces the gas diffusion barrier, GO-SPLM significantly enhances the permeability of gas.

Preparation of Porous Liquid Based on Silicalite-1

Solid porous materials, like zeolites, have been widely used in a variety of fields such as size-and-shape-selective absorption/separation and catalysis because of their porosity. However, there are few liquid materials that exhibit permanent porosity. Porous liquids are a novel material that combine the properties of fluidity and permanent porosity. They have potential applications in many fields such as gas separation, storage and transport. Herein, we report a novel Type 1 porous liquid prepared based on silicalite-1. The pore size of this porous liquid was determined by positron annihilation lifetime spectroscopy (PALS), and the CO₂ capacities were determined by the intelligent gravimetric analyzer (IGA). The unique properties of this porous liquid can promote its application in many fields such as gas storage and transport.