Shining Light on Porous Liquids: From Fundamentals to Syntheses, Applications and Future Challenges

Abstract

Porous liquids (PLs), an emerging type of flowing liquid materials that combine the merits of porous solids and flowing liquids, have garnered immense attention since the concept of PLs was proposed in 2007. Meanwhile, PLs have witnessed growing success in versatile synthesis strategies and emerging applications, especially since 2017. Given the lack of a timely comprehensive review, developing a prompt summary with a comprehensive understanding is undoubtedly urgent. Thus, this critical review offers a comprehensive summary of the progress in fundamental chemistry, developmental history, synthetic strategies, and emerging applications of PLs. First, the fundamental chemistry and developmental history are reviewed. Then, the synthesis strategies of PLs are highlighted. Additionally, crosscutting studies of pure theoretical simulations are reviewed. Meanwhile, the daunting characterization issues of PLs are analyzed. Next, the state-of-the-art of PLs applications is reviewed in detail. In the end, perspectives regarding the remaining challenges and future directions for PLs are presented. It is speculated that this critical comprehensive review of PLs could inspire scientific communities who focus on the taskspecific materials for various applications, such as gas sorption, membrane separation, catalytic conversion, chiral separation, thermal management and electrolyte, and so on.

Porous liquids – the future is looking emptier

“… 25 In addition, while the formation of a melt-quenched glass with glass transition was not formally noted, it is also worthwhile to mention that one of the alkylated POCs from the initial type I porous liquid study was reported to also have a glassy appearance, namely the n -octyl decorated POC. 21 …”

“…25 In addition, while the formation of a melt-quenched glass with glass transition was not formally noted, it is also worthwhile to mention that one of the alkylated POCs from the initial type I porous liquid study was reported to also have a glassy appearance, namely the n-octyl decorated POC. 21 It was not until 2015 that the rst systems formally identied as porous liquids were reported, where both type I and type II porous liquids, based on hollow silica spheres and POCs respectively, were realised. 26,27 Building on the initial attempts at forming porous liquids using POCs, two different strategies were employed to improve their solubility, as opposed to inducing melting, enabling high concentration type II porous liquids to be formed on dissolution in cavity-excluded solvents (Fig.…”

“…Among other recent reviews, this work aims to lay out the key concepts and approaches that are important in developing and understanding porous liquids, rather than expanding on the classications. 16 However, previous reviews have predominantly focused on outlining the early examples of materials in this class and how new porous liquids may be developed, [13][14][15] have given an extensive and exclusive summarisation of the porous liquid literature, 21 or have focused on the important physical properties of porous liquids that make them candidates for certain applications. 22 In contrast, we hope this provides readers with a short and accessible review to understand the parallel concepts employed in the discovery of porous liquids as well as the breadth of potential applications.…”

Practical considerations in the design and use of porous liquids

“…Catalysis by PLs possesses both advantages and can achieve high selectivities for many industrial separations. 125,126 Recently, porous solids have been used to protect catalysts in PL catalysis, as represented in Fig. 9.…”

Post-synthetic modification of UiO-66-OH toward porous liquids for CO2 capture

“…Consequently, PLs have shown excellent prospects, especially in gas adsorption, [17][18][19][20][21] separation [22][23][24][25] and catalysis, 26 etc. Until now, PLs based on various types of pore generators and sterically hindered solvents have been successively reported, such as ionic liquid encapsulated nano hollow spheres porous liquid materials, 27 alkyl modified cavity tetrahedral crystal porous liquid materials, 28 porous solid materials dissolved in macromolecular solvents, [29][30][31] and so on. For example, Li reported a new class of PLs using internally functionalized metal-organic framework (MOF) particles as pore generators and polydimethylsiloxane (PDMS) as sterically hindered solvents.…”