Metal–Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols

Abstract

Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal−organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H 2 . The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl 2 followed by the reaction of NaEt 3 BH. X-ray photoelectron spectroscopy and X-ray absorption nearedge spectroscopy (XANES) indicated the presence of Co II and Al III centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt−hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H 2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.

Chemoselective and Tandem Reduction of Arenes Using a Metal–Organic Framework-Supported Single-Site Cobalt Catalyst

“…The reaction of AlCl 3 ·6H 2 O and 4,4′-biphenyldicarboxylic acid (H 2 bpdc) in dimethylformamide (DMF) at 120 °C produced DUT-5 MOF as a white crystalline solid having a formula of [Al­(OH)­(bpdc)] with rhombic channels . The deprotonation of μ 2 -OH of SBUs of DUT-5 by n -BuLi followed by reaction with CoCl 2 in tetrahydrofuran (THF) at room temperature gave SBU-supported cobalt chloride species (DUT-5-CoCl) . The treatment of NaEt 3 BH with DUT-5-CoCl at room temperature afforded the corresponding DUT-5 node-supported Co-hydride species (DUT-5-CoH) via a halide-hydride exchange (Figure a) .…”

“…94 The deprotonation of μ 2 -OH of SBUs of DUT-5 by n-BuLi followed by reaction with CoCl 2 in tetrahydrofuran (THF) at room temperature gave SBUsupported cobalt chloride species (DUT-5-CoCl). 95 The treatment of NaEt 3 BH with DUT-5-CoCl at room temperature afforded the corresponding DUT-5 node-supported Cohydride species (DUT-5-CoH) via a halide-hydride exchange (Figure 1a). 95 The cobalt loading of 29% with respect to bridged hydroxy groups at SBUs of DUT-5-CoH was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES).…”

“…95 The treatment of NaEt 3 BH with DUT-5-CoCl at room temperature afforded the corresponding DUT-5 node-supported Cohydride species (DUT-5-CoH) via a halide-hydride exchange (Figure 1a). 95 The cobalt loading of 29% with respect to bridged hydroxy groups at SBUs of DUT-5-CoH was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The crystallinity and structure of MOF remained intact after metalation and the halide-hydride exchange as displayed by the similar powder X-ray diffraction (PXRD) patterns between pristine DUT-5, DUT-5-CoCl, and DUT-5-CoH (Figure 1b).…”

Heterogenized Molecular Rhodium Phosphine Catalyst within Metal-Organic Framework for Ethylene Hydroformylation

“…8 Moreover, the MOF extended crystalline network allows for combining crystallographic techniques with computational studies to elucidate catalytic site nature and molecular catalytic mechanisms at play inside the porosity. [9][10][11][12][13][14][15][16][17][18][19] In molecular catalysis, phosphines are widely used ligands whose both electronic and steric properties strongly influence the catalytic activity of the bound metal cation. 20 Phosphines have become essential to drive the catalytic activity and selectivity in applications ranging from fine chemistry with asymmetry and C-C coupling reactions, to petrochemistry with valorization of olefins using catalyzed oligomerization, hydroformylation, hydrogenation and metathesis.…”

Chiral Iron(II)-Catalysts within Valinol-Grafted Metal–Organic Frameworks for Enantioselective Reduction of Ketones

“…Chiral 1,2-amino alcohols are versatile structural motifs widely present in biologically active molecules. − Although chiral 1,2-amino alcohols are easily affordable by reducing naturally occurring amino acids, their application as chiral bidentate ligands in base-metal catalysis is very limited, presumably due to the absence of sterically bulky substituents that leads to the formation of oligomeric metal species or intermolecular decomposition. − In asymmetric catalysis, amino acid-derived 1,2-amino alcohols have been primarily employed as chiral auxiliaries or the source of a stereogenic center in the ligand component of the base-metal catalysts, − or ligands after multistep derivatization. ,, Grafting of amino alcohols onto porous solid supports followed by metalation could provide robust single-site earth-abundant metal catalysts that would impose excellent chiral induction within pores for enantioselective catalysis. As a porous and tunable molecular material, metal–organic frameworks (MOFs) have emerged as an interesting class of supports to prepare heterogeneous and robust chiral base-metal catalysts via active-site isolation. − Owing to their modular and tunable properties, the chemoselectivity and enantioselectivity of chiral MOF-catalysts could be easily optimized by adjusting pore sizes and postsynthetic modification techniques. ,, In addition, the precise knowledge of crystalline MOF structures by X-ray crystallography provides distinct advantages over other supported chiral catalysts by enabling rational tuning of catalytic activities/selectivities through the use of tailor-made building blocks and direct observation of structure–activity relationships.…”