Porous Liquids Open New Horizons: Synthesis, Applications, and Prospects

Abstract

Conspectus Though the idea of liquids with accessible porosity seems counterintuitive, porous liquids (PLs) have indeed demonstrated themselves to hold great promise in versatile fields, thus arousing great attention and interests from both academic and industrial communities since the concept of PLs was first proposed in 2007. PLs are a novel class of a flowing liquid system that possesses accessible permanent porosity, and they integrate the processable advantages of liquids with superior accommodative capacities of porous solids. By and large, the development of PLs went through the starting stage of the concept proposal and the arrival stage of various synthesized examples to the period of application-specific extensions. From the point of view of producing functions, PLs consist of two parts: sterically hindered solvents and pore generators. Correspondingly, pore generators provide accessible cavities for the resultant PLs, while sterically hindered solvents endow pore generators with a flowing behavior. Undoubtedly, engineering permanent porosity with shape-persistent cavities into a liquid is leading to an inherent change that porosity can not only be created in conventional solids, thus providing new opportunities by utilizing the processability of PLs. Therefore, the field of PLs has seen considerable progress in the design, synthesis, and emerging applications since the example of hollow silica based PLs was demonstrated by Dai et al. in 2015 (Porous Liquids: A Promising Class of Media for Gas Separation.Angew. Chem., Int. Ed. Engl.201554932936), especially during the past four years. Until now, PLs have emerged as promising platforms for a variety of applications, including but not limited to gas capture, molecule separation, catalytic conversion, biomedicine, and beyond. Anyhow, the further development toward practical applications of PLs depends heavily on the universal synthesis method and the process optimization, where the former is undoubtedly the core. This Account mainly showcases the evolution of our recent progress in the design and synthesis of PLs. Importantly, we tell the story of how we apply the synthesis idea of another similar liquidlike material (i.e., solvent-free nanofluids, SFNs) that has been investigated for more than 20 years in our laboratory in the preparation of PLs. Emphasis is put on the construction of PLs from the perspective of interface interactions (e.g., the electrostatic interaction, the acid–base interaction, and the dipole–dipole/quadrupole interaction, etc.) between sterically hindered solvents and pore generators. Then, we present and summarize related applications in the field of environmental remediation including gas sorption, membrane separation, metal ion selective sorption, and extractive desulfurization, etc. Finally, the challenges, opportunities, and future directions in developing novel PLs are provided and outlined. It is expected that this Account will stimulate the interest of researchers working in broadly diverse fields to fully unleash the potent...

Lead Extraction in a Functionalized and Permeable Silica-Based Porous Liquid

“…Despite their high potential, applications of PLs are nearly always restricted to gas sorption and gas separation, even when the host particles are large. ,, While metal extraction using solid porous silica or other similar materials is well developed, , it is surprising that very little research has been conducted to date with LPs . PLs were recently considered for metal adsorption.…”

“…2,8,9 While metal extraction using solid porous silica or other similar materials is well developed, 10,11 it is surprising that very little research has been conducted to date with LPs. 12 PLs were recently considered for metal adsorption. Hemming et al have shown the possibility of encapsulating nanoparticles of gold, platinum, and palladium during the synthesis of a functionalized silicabased PL with the aim of developing a liquid support for heterogeneous catalysis.…”

The Role of the Nanoconfinement Effect in the Adsorption of Carbon Dioxide by Porous Liquids

“…As an emerging type of liquid material, porous liquids (PLs) have attracted much attention in the past decade due to their great ability of gas adsorption and separation. − Porous liquids introduced fluid properties into the porous solid, combining the advantages of both porous solids and liquids. − ,− Porous solids such as porous organic cages (POCs), − metal–organic frameworks (MOFs), − or zeolitic imidazolate frameworks (ZIFs) provide permanent porosity with rich gas adsorption behaviors. − Meanwhile, liquids have a great ability to dissipate heat during adsorption and regeneration processes. , Also, liquids do not suffer from mechanical fatigue or physical aging, which is common in solid materials. , As of today, four types of porous liquids have been applied to gas adsorption or separation. − ,, Type I PL is a neat liquid composed of one type of molecule that provides permanent intrinsic porosity. − Type II PL combines the porous host and solvent, such as the porous organic cages solvated in the sterically hindered crown-ether liquids. − Type III PL shares the same combination method as that of type II PL, while the solutes in type III PL usually are nanoparticles instead of organic cages. − , Type IV PL is another single-component liquid with a lower melting point at room temperature . Among them, type II and type III PLs attract much attention due to the large combination of the porous host and solvent, which provides potential tunable applications for gas capture. , …”

Converting Nanoflower-like Layered Double Hydroxides into Solvent-Free Nanofluids for CO2 Capture

“…These new SFNs have significant liquid flow behavior at room temperature without any solvents, as a result of the organic oligomers functioning as fluidic media to ensure mobility. During the past decade, various studies have shown that SFNs bring better dispersion of core particles due to their fluidity and the potential resistance effect of organic oligomer chains, also providing better support for their applications in different fields, such as tribology, flame retardant, sensor, energy storage, , gas capture, − etc.…”