Exploring structure and reactivity of Cu sites in functionalized UiO-67MOFs

tThe exceptional thermal stability of the UiO-67/68-family MOFs makes them ideal candidates to explorepost-synthetic functionalization routes aiming to the heterogenization of homogeneous catalysts. Wepreviously demonstrated that a small fraction of the linkers in the UiO-67 MOF can be replaced bybipyridine-dicarboxylate (bpydc) moieties exhibiting metal-chelating ability and enabling the graftingof Pt(II) and Pt(IV) ions in the MOF framework [Chem. Mater., 27 (2015) 1042]. Herein, we investigate anovel Cu-functionalized UiO-67 MOF obtained by a simple synthesis method, consisting in contacting thebpydc-containing UiO-67-bpy MOF with a CuCl2dihydrate precursor. By combining in situ and operandoXAS and FTIR spectroscopies, we assessed the successful incorporation of well-defined Cu complexes inthe UiO-67 framework and explored local coordination geometry, redox properties and reactivity of thedominant Cu species formed in different conditions relevant to potential future applications in catalysis.EXAFS fits and XANES simulations, based on DFT-optimized geometries, yielded detailed structural andelectronic information on the major Cu-species formed. Data analysis revealed three-coordinated Cu(I)complexes with the bpydc linker of the Cu-UiO-67 MOFs and a Cl−ligand, formed after thermal treatmentat 523 K in inert gas flow able to efficiently and reversibly form Cu(I)-mono-carbonyl adducts with COadsorbate.