Postsynthetic Modification of Zn/Co-ZIF by 3,5-Diamino-1,2,4-triazole for Improved MOF/Polyimide Interface in CO₂–Selective Mixed Matrix Membranes
2022
Loloei, Mahsa | Kaliaguine, Serge | Rodrigue, Denis
Amine-functionalized zeolite imidazolate frameworks (ZIF) are known to improve the mixed matrix membranes (MMM) separation performances for CO₂/CH₄ applications. In this study, 3,5-diamino-1,2,4-triazole, a ligand with −NH₂ functionality and uncoordinated −NH group, was used in the postsynthetic modification of dual metal Zn/Co-ZIF for partial substitution of 2-methylimidazole to obtain a biligand Zn/Co-ZIF (Zn/Co-TZ₁ₕ) with retained crystallinity, tunable pore size and enhanced CO₂ adsorption capacity. A series of mixed matrix membranes were then fabricated at a single concentration (7.5 wt %) of parent Zn/Co-ZIF or Zn/Co-TZ₁ₕ in 6FDA-ODA or Matrimid polyimides to compare the effect of modified ZIF to its unmodified analogue on the MMM properties and CO₂/CH₄ separation performance. Zn/Co-TZ₁ₕ MMM showed enhanced mechanical properties and better filler integration into the polymer matrix as a result of better interfacial interactions via hydrogen bonding while retaining the same thermal stability as Zn/Co-ZIF MMM. Moreover, the combination of ZIF gate size control, improved size discrimination, and specific chemical interaction gave the NH₂-functionalized Zn/Co-ZIF MMM the possibility to significantly overcome the CO₂/CH₄ separation performance of the pure polymer. Postsynthetic modification of ZIF by amine-functionalized ligands can be an effective strategy to improve the filler/polymer interface quality resulting in improved MMM separation properties.
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