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Porous liquids (PLs), a new class of materials with permanent pores and macroscopic flowing behaviors, have attracted much attention for CO2 capture. However, the preparation of PLs is always complicated, which is not suitable for the scale-up. Herein, we propose a rather simple and feasible strategy based on post-synthetic modification of pore generators and the like-dissolves-like principle to synthesize UiO-66-PLs with low-viscosity. To be specific, the metal–organic framework (MOF) UiO-66 with hydroxyl groups (denoted UiO-66-OH) was modified by an organosilane (denoted KH550 or SID) via a post-synthetic modification method, obtaining the pore generator UiO-66-OS (denoted UiO-66-KH550 or UiO-66-SID). Then, the UiO-66-OS was dispersed into two different sterically hindered polydimethylsiloxane solvents (PDMS400 or PDMS6000). Thereby, a series of type 3 PLs (UiO-66-PLs) with superior fluidity at room temperature and accessible porosity were obtained. For instance, the viscosities of UiO-66-KH550-PDMS400 and UiO-66-SID-PDMS400 were 1.1 and 1.5 Pa S at 25 °C, respectively, which were far lower than those of values reported thus far. In addition, gas sorption–desorption measurements indicated that the UiO-66-PLs exhibit superior CO2 sorption performance and great potential for CO2/N2 separation. Moreover, molecular simulation was carried out to verify the retained accessible porosity. Notably, the strategy of constructing type 3 PLs based on the post-synthetic modification of MOFs with organosilane and the like-dissolves-like principle not only provides a new solution for the development of low-viscosity PLs, but also opens a new path for the construction of other types of advanced porous material (APM)-based (e.g., covalent organic frameworks (COFs), porous organic cages (POCs)) PLs, which have potential applications in the fields of gas trapping storage, and catalysis. [ABSTRACT FROM AUTHOR]

Nanoparticle organic hybrid materials (NOHMs) have shown great potential as absorbents for CO2 capture owing to their attractive properties, including macroscopic liquid-like behavior, good dispersion properties, and tunable structures. However, only a few NOHMs are used as fillers to prepare mixed-matrix composite membranes (MMMs) for CO2 capture. Here, we demonstrated novel MMMs comprising a Pebax-1657 polymer matrix and NOHM fillers for separating a CO2/N2 mixture. Various types of NOHMs with a core/corona/canopy structure based on a CNT/SiO2 composite core were prepared and incorporated into the Pebax-1657 matrix. In particular, the effect of the composite core composition on CO2/N2 mixture permeation was systematically investigated. Benefiting from the dispersion properties of liquid-like NOHMs, excellent interfacial compatibility was obtained. Furthermore, functional groups on the canopy of NOHMs were confirmed to enhance the CO2-philic properties for separation. Specifically, the as-prepared membrane presented optimal performance regarding CO2 permeability (148.3 Barrer) and the separation factor (66.5 for CO2/N2), while also showing improvements in CO2 permeability by 142.3% and the CO2/N2 separation factor by 62.5% compared with neat Pebax membrane, overcoming the Robeson upper bound. Finally, the influence of the composite core composition (CNT/SiO2 weight ratio) in NOHMs on CO2 selective separation was investigated. A possible CO2 selective separation mechanism was also proposed. [ABSTRACT FROM AUTHOR]