Transforming Metal–Organic Frameworks into Porous Liquids via a Covalent Linkage Strategy for CO₂ Capture

Abstract

Porous liquids (PLs), an emerging kind of liquid materials with permanent porosity, have attracted increasing attention in gas capture. However, directly turning metal−organic frameworks (MOFs) into PLs via a covalent linkage surface engineering strategy has not been reported. Additionally, challenges including reducing the cost and simplifying the preparation process are daunting. Herein, we proposed a general method to transform Universitetet i Oslo (UiO)-66-OH MOFs into PLs by surface engineering with organosilane (OS) and oligomer species via covalent bonding linkage. The oligomer species endow UiO-66-OH with superior fluidity at room temperature. Meanwhile, the resulting PLs showed great potential in both CO 2 adsorption and CO 2 /N 2 selective separation. The residual porosity of PLs was verified by diverse characterizations and molecular simulations. Besides, CO 2 selective capture sites were determined by grand canonical Monte Carlo (GCMC) simulation. Furthermore, the universality of the covalent linkage surface engineering strategy was confirmed using different classes of oligomer species and another MOF (ZIF-8-bearing amino groups). Notably, this strategy can be extended to construct other PLs by taking advantages of the rich library of oligomer species, thus making PLs promising candidates for further applications in energy and environment-related fields, such as gas capture, separation, and catalysis.

Hollow Silica‐Based Porous Liquids Functionalized Mixed Matrix Membranes for CO2 Capture

“…The as‐prepared MOP PLs presented improved gas transport due to the accessible cavities. More recently, Wang et al [19] . synthesized a class of UiO‐66 PLs via a covalent linkage strategy and the PLs can serve as free space to gas molecules and improve gas uptake.…”

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

“…More recently, our group [56] reported a general strategy to turn UiO-66 MOF into PLs via the covalent bonding linkage (Figure 14a). To be specific, firstly, the polyether amine (M2070) reacted with an OS (KH560) the covalent linkage.…”

“…Reproduced with permission. [56] Copyright 2021, American Chemical Society. b) The synthesis of cyclodextrin PL.…”

“…Following this study, in 2020, our group designed Type 1 PLs with core-corona-canopy structure. To be specific, UiO-66 MOF PLs were prepared using organosilane (OS) and oligomer polyether amine [56] (Figure 21c). The as-prepared UiO-66-liquid-M2070 PL was then incorporated into the Pebax-1657 polymer matrix to prepare MMMs for CO 2 /N 2 separation.…”

Composite Porous Liquid for Recyclable Sequestration, Storage and In Situ Catalytic Conversion of Carbon Dioxide at Room Temperature

“…For example, MOFs and zeolites with microporous/mesoporous frameworks have been utilized as host molecules in bulky ionic liquid medium to form another type of microporous/mesoporous liquids [35–43] . Further, meso‐ and microporous liquids have also been designed by surface engineering MOFs with oligomer species or polyethylene glycol, and also by the dissolution of MOFs in other solvents such as crown ethers and poly(dimethylsiloxane) [44–47] . Highly stable 3D‐imine‐linked colloidal covalent organic framework (COF) based porous liquid have been developed with increased CO 2 and CH 4 uptake capacity [48] .…”