Metal-organic frameworks (MOFs) offer an unprecedented degree of structural and chemical tunability, making them promising platforms for the design of single-site heterogeneous catalysts. This presentation will describe our recent efforts to design MOFs containing immobilized Fe and Co 2,6-pyridine dicarboxamide (PDCA) complexes. Although these simple dianionic pincer ligands have rich precedent for supporting reactive Ni and Cu species, their chemistry with Co and Fe has been severely underdeveloped owing to a propensity for formation of bis-chelate complexes. Thus, MOF-immobilization provides a means to isolate and explore the reactivity of mono-chelate complexes that are not readily accessible as homogeneous species. Amide coupling reactions have been used to append PDCA ligands at the amine-tagged linkers of MIL-101-NH2(Al). The products have been characterized using 1H NMR and infrared spectroscopy, indicating that ~50% of the amine-tagged linkers are functionalized with PDCA groups. Subsequent postsynthetic metalation with iron(II) acetate and cobalt(II) acetate affords immobilized PDCA-M (M=Co, Fe) complexes. N2 gas-adsorption measurements show a drop in Braunauer-Emmett-Teller (BET) surface area from 2337 m2/g to 1233 m2/g after installation of the PDCA-M complexes. Ongoing work is focused on investigating the reactivity and catalytic activity of these new materials.

Designing MOFs with immobilized pyridine-dicarboxamide complexes

ACS Fall 2021

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