The Zr6O4(OH)4 cluster in Zr-based MOFs, which are well-known for their high stabilities under a broad range of conditions, has recently been shown to be active sites for the capture of environmental contaminants as well as catalysts for oxidation reactions, especially as the Zr-OH moiety can be transformed into active Zr-OOH active species. However, the overall catalytic activity of UiO-66, the prototypical MOF in this group of materials, was limited by its intrinsic small pore sizes (aperture ~ 6 Å) which restrict the access of the substrate to sites that are below the surface of the MOF microcrystals. To overcome these challenges, we have synthesized hierarchically mesoporous (HM) UiO-66 materials (UiO-66@HM-UiO-66-X, X = F4, (OH)2, (COOH)2, etc.) using a template-assisted, seed-mediated strategy, in which a UiO-66 nanoparticle (NP) seed core is encapsulated in an HM-UiO-66-X shell with mesopores (~8 nm) (see attached Figure). Notably, the incorporation of mesopores into the thrice-overgrown UiO-66@HM|3rd-UiO-66-F4 materials lead to impressive enhancements in the per-mass uptake capacity of Direct Blue 86, a large anionic dye: 320% better than the parent UiO-66 seeds and 150% better than that for a [UiO-66 + UiO-66-F4] physical mixture at the same mass proportion. Similar enhancements were also observed in the catalyzed oxidation of thioanisole.

Template-assisted, seed-mediated synthesis of hierarchically mesoporous core-shell UiO-66: enhancing adsorption capacity and catalytic activity through iterative growth

ACS Fall 2020 Virtual Meeting

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