Assembly of dicobalt and cobalt–aluminum oxide clusters on metal–organic framework and nanocast silica supports

Abstract

NU-1000, a mesoporous metal-organic framework (MOF) featuring hexazirconium oxide nodes and 3 nm wide channels, was infiltrated with a reactive dicobalt complex to install dicobalt active sites onto the MOF nodes. The anchoring of the dicobalt complex onto NU-1000 occurred with a nearly ideal stoichiometry of one bimetallic complex per node and with the cobalt evenly distributed throughout the MOF particle. To access thermally robust multimetallic sites on an all-inorganic support, the modified NU-1000 materials containing either the dicobalt complex, or an analogous cobalt-aluminum species, were nanocast with silica. The resulting materials feature Co or Co-Al bimetallated hexazirconium oxide clusters within a silica matrix. The cobalt-containing materials are competent catalysts for the selective oxidation of benzyl alcohol to benzaldehyde. Catalytic activity depends on the number of cobalt ions per node, but does not vary significantly between the NU-1000 and silica supports. Hence, the multimetallic oxide clusters remain site-isolated and substrate-accessible within the nanocast materials.

Well-Defined Rhodium–Gallium Catalytic Sites in a Metal–Organic Framework: Promoter-Controlled Selectivity in Alkyne Semihydrogenation to E-Alkenes

“…Powder X-ray diffraction studies and N 2 sorption isotherms further confirm the crystallinity and porosity of 1 (1545 cm 2 / g) and 2 (1637 cm 2 /g), 1990 cm 2 /g for NU-1000 (Figure 1c). 9,10 The 1 H NMR spectra of D 2 SO 4 -digested 1 and 2 each show D 3 py 3 tren in a mole ratio of 1 ligand per 2 linkers, which is equivalent to 1 ligand per node (Figure S9). The HAADF-STEM images of 1 and 2 reveal that the modified MOF particles retain the overall shape and morphology of pristine NU-1000 particles (Figure 1e).…”

Mechanistic Study on the Origin of the Trans Selectivity in Alkyne Semihydrogenation by a Heterobimetallic Rhodium–Gallium Catalyst in a Metal–Organic Framework

“…Previously, postsynthetic incorporation of well-defined heterobimetallic active sites into MOFs was achieved by reacting a metal–metal-bonded organometallic coordination complex and NU-1000, which is a MOF of Zr 6 -oxide clusters and tetrakis­( p -benzoate)­pyrene linkers (Figure a). − An immobilized heterobimetallic Rh-Ga complex with an intact Rh→Ga bonding interaction (Figure b,c) demonstrated excellent chemo- and regioselectivity in catalytic alkyne semihydrogenation to alkenes, where acyclic internal alkynes were transformed to the corresponding alkenes with E : Z ratios >98:2 . We proposed that the Ga ion acts as both an electronic and structural promoter.…”

Computational Design of Functionalized Metal–Organic Framework Nodes for Catalysis

“…Mixed-metal structures can also be synthetically accessed as recently shown for Co­(II)­Al­(III)-functionalized NU-1000 nodes. , Precoating of MOF nodes with aluminum-oxide clusters and subsequent functionalization with Ir­(I) precursors presents a major challenge to structural characterization, with extensive calculations suggesting that Al x O y clusters and Ir may attach to different faces of individual nodes . Transition metal complexes can also be attached to MOF nodes via SALI …”