Single-Site Cobalt Catalysts at New Zr₈(μ₂-O)₈(μ₂-OH)₄ Metal-Organic Framework Nodes for Highly Active Hydrogenation of Alkenes, Imines, Carbonyls, and Heterocycles

Abstract

We report here the synthesis of robust and porous metal-organic frameworks (MOFs), M-MTBC (M = Zr or Hf), constructed from the tetrahedral linker methane-tetrakis(p-biphenylcarboxylate) (MTBC) and two types of secondary building units (SBUs): cubic M8(μ2-O)8(μ2-OH)4 and octahedral M6(μ3-O)4(μ3-OH)4. While the M6-SBU is isostructural with the 12-connected octahedral SBUs of UiO-type MOFs, the M8-SBU is composed of eight M(IV) ions in a cubic fashion linked by eight μ2-oxo and four μ2-OH groups. The metalation of Zr-MTBC SBUs with CoCl2, followed by treatment with NaBEt3H, afforded highly active and reusable solid Zr-MTBC-CoH catalysts for the hydrogenation of alkenes, imines, carbonyls, and heterocycles. Zr-MTBC-CoH was impressively tolerant of a range of functional groups and displayed high activity in the hydrogenation of tri- and tetra-substituted alkenes with TON > 8000 for the hydrogenation of 2,3-dimethyl-2-butene. Our structural and spectroscopic studies show that site isolation of and open environments around the cobalt-hydride catalytic species at Zr8-SBUs are responsible for high catalytic activity in the hydrogenation of a wide range of challenging substrates. MOFs thus provide a novel platform for discovering and studying new single-site base-metal solid catalysts with enormous potential for sustainable chemical synthesis.

Catalytic Transfer Hydrogenation of Biomass‐Derived Carbonyls over Hafnium‐Based Metal–Organic Frameworks

“…Hf-MOF-808 with the trimesate linker makes use of formic acidf or its preparation. [20] Regarding the catalytic applications, Hf-MOFsh ave been used as catalyst supports forR h I complexes for the catalytic hydrogenation of ethylene, [22] cobalt species are able to catalyze ab road scope of hydrogenation reactions, [23] and organozirconiums ingle-site components are promising catalysts for ethylene and stereoregular 1-hexenep olymerization. [24] Catalysis at the linker in Hf-MOFs has also been reported for the selective dehydration of fructose to 5-hydroxymethylfurfural by the sulfonic-acid functionalized MOF NUS-6(Hf), [25] for the hydrosilylation of terminal olefins by a2 ,2',2''-terpyridine-iron complex included as ab ridging ligand in aH fm etal-organic layered material, [26] and for the conversion of CO 2 andepoxides into cyclic carbonates at ambient conditions by Cu porphyrin included in theH fm etal-organic framework named FJI-H7.…”

Size effect of the active sites in UiO-66-supported nickel catalysts synthesized via atomic layer deposition for ethylene hydrogenation

“…23 Depending, of course, on their specific chemical composition, the resulting MOF-supported clusters or single metal ions can be rendered competent for photocatalytic H 2 generation, 24 electrocatalytic O 2 production, 25 solution-phase alkene epoxidation, 26, 27 and gas-phase ethylene hydrogenation and oligomerization, 13, 21, 28 hexene polymerization, 20 and propane oxidative dehydrogenation, 29 among other reactions. 22, 30 …”

Heterogeneous Epoxide Carbonylation by Cooperative Ion-Pair Catalysis in Co(CO)4–-Incorporated Cr-MIL-101

“…Other innate properties of Cr-MIL-101 that we deemed favorable for catalysis were its high hydrothermal and chemical stability, large surface area (4100 m 2 /g as measured by N 2 adsorption), large windows (12 and 16 Å) and pores (29 and 34 Å) for ready diffusion of reaction species, site-isolation of the Lewis acidic Cr(III) centers for robust catalysis, and facile synthesis using inexpensive chromium and terephthalic acid precursors. 21 Similar strategies to leverage the intrinsic stability, 22,23 porosity, 24,25 and site-isolation 26−28 of MOFs have proven to be effective in their applications to heterogeneous catalysis. Therefore, postsynthetic ion exchange of Co(CO) 4 – into Cr-MIL-101 was sought for the formation of a heterogeneous [Lewis acid] + [Co(CO) 4 ] − system.…”