PIM-based mixed matrix membranes containing covalent organic frameworks/ionic liquid composite materials for effective CO2/N2 separation

The development of high-performance CO2 capture membranes is an urgent requirement to combat the greenhouse effect and climate change. Covalent organic frameworks (COFs) with highly ordered porous structure and modifiable pore environment shows substantial potential in the field of membrane separation. Nevertheless, the scarce affinity sites and large pore diameters of COFs may limit their effect on gas separation in membranes. In the present work, TPB-DMTP-COF was modified with imidazolium-based ionic liquid [Emim][Tf2N] (IL) to remedy such disadvantages of COFs and then the mixed matrix membranes (MMMs) were prepared by introducing IL@COF into PIM-1. The IL modification not only can endow the TPB-DMTP-COF with better CO2 affinity and narrowed pore size, but also can further improved interfacial compatibility among PIM-1 and TPB-DMTP-COF. Therefore, the introduction of IL@COF into PIM-1 membrane can leads to an increase in CO2/N2 separation properties of the obtained membranes. Notably, 3.0 wt% IL@COF/PIM-1 MMMs show optimal CO2 permeability and CO2/N2 selectivity of 9137.7 Barrer and 20.2, respectively. Such high separation performance exceeds 2008 Robeson upper bound. Moreover, the resultant MMMs also exhibit favorable continuous operation stability. Overall, the combination of IL and COFs may provide a new inspiration for designing efficient CO2 separation MMMs.