Journal of Catalysis, Vol.392, 80-87, 2020
Engineering functional group decorated ZIFs to high-performance Pd@ZIF-92 nanocatalysts for C(sp(2))-C(sp(2)) couplings in aqueous medium
Herein the first ever Pd2+-decorated ZIF-92 nanostructure is readily accessed by post-synthesis modification (PSM) of the zeolitic imidazolate framework ZIF-90. Thus, the imidazolate linker of the ZIF-90 is functionalized with the hydroxyethylimino group, followed by anchoring the palladium catalytically active sites through a tight coordination of Pd2+ ions to both the N and O atoms of ZIF-92. The acquired data (by PXRD, EDS, SEM, XPS, ICP-AES) concerning the crystalline structure, elemental mapping and network configuration of the Pd@ZIF-92 catalyst confirmed its structure, before and after the cross-coupling reactions and following recycling. The Pd@ZIF-92 showed excellent catalytic activity (>99%) and chemoselectivity in Suzuki-Miyaura coupling proceeding in neat water, at very low Pd loading (0.009 mol%). Comparison of its performance with that of many reported Pd nanocatalysts operating in aqueous/protic media testifies to its superiority. The appealing gateway to this innovative, stable, robust, easily recoverable and reusable Pd@ZIF-92 nanostructure recommends its beneficial utilization in C(sp(2))-C(sp(2)) cross couplings and other sustainable, environmentally-friendly processes. (C) 2020 Elsevier Inc. All rights reserved.
Keywords:1-st Pd-ZIF-92 heterogeneous catalyst;MOFs, PSM;C-C cross-couplings;Low palladium loading;Benign water medium