Superior performance of Co-N/m-C for direct oxidation of alcohols to esters under air

Heterogeneous M-N-C Catalysts for Aerobic Oxidation Reactions: Lessons from Oxygen Reduction Electrocatalysts

“…In these studies, atomically dispersed CoN x species were not considered as an alternative. Co appears to be privileged for this reactivity on the basis of screening studies, which evaluated benzyl alcohol methyl esterification over a range of M-N-C­(iv) catalysts (M = Co, Fe, Cu, V, Cr, Ni, Mn) and M-N-C­(i) catalysts (M = Fe, Mn, Co Cu). Co-N-C catalysts competent for esterification have been synthesized by a variety of methods noted in Figure a, including (i), ,,,, (ii), (iii), , (iv), and (v). ,, These studies have observed CoO x nanoparticles, ,,,, metallic Co nanoparticles ,, (often with N–C shells ,,,,, ), and an absence of large metal aggregates that suggests the presence of mononuclear CoN x species. , Quantitative relationships between active site structures and reactivity have not been established.…”

“…Normalized rates (per total Co, 60 °C, 1 bar O 2 ) for the methyl esterification of benzyl alcohol are higher under conditions with added base. Among the three catalysts that have been tested in the presence and absence of base, ,, the Co-N-C­(iv) of Gao and co-workers has the highest normalized rate with added base (9 × 10 –2 mol (mol Co) −1 s –1 ), 732 whereas the Co-N-C­(i) of Li et al has the highest normalized rate in the absence of exogenous base (2 × 10 –3 mol (mol Co) −1 s –1 ) . That the optimal catalyst is different in the presence and absence of base implicates mechanistic distinctions that have not yet been elucidated.…”

“…62 In these studies, atomically dispersed CoN x species were not considered as an alternative. Co appears to be privileged for this reactivity on the basis of screening studies, which evaluated benzyl alcohol methyl esterification over a range of M-N-C(iv) catalysts 73 (M = Co, Fe, Cu, V, Cr, Ni, Mn) and M-N-C(i) catalysts 62 (M = Fe, Mn, Co Cu). Co-N-C catalysts competent for esterification have been synthesized by a variety of methods noted in Figure 2a, including (i), 60,62,67,69,72 (ii), 74 (iii), 75,76 (iv), 73 and (v).…”

“…68,71,77 These studies have observed CoO x nanoparticles, 60,67,69,74,77 metallic Co nanoparticles 60,74,77 (often with N−C shells 62,67,68,71,72,76 ), and an absence of large metal aggregates that suggests the presence of mononuclear CoN x species. 73,75 Quantitative relationships between active site structures and reactivity have not been established.…”

Heterogeneous Iron-Catalyzed Aerobic Oxidative Cleavage of C–C Bonds in Alcohols to Esters

“…In recent years, metal−N−C materials have emerged as promising catalysts for various organic transformations. 39−45 In this regard, we have demonstrated that carbon-supported cobalt−nitrogen materials constitute highly active catalysts for the cross-coupling of alcohols with amines to imines, 46 the selective oxidation of alcohols to esters or nitriles, 47,48 and the oxidative cleavage of C−C bonds in alcohols to esters 38 and that carbon-supported iron−nitrogen materials constitute catalysts for the oxidative cleavage of C�C bonds in olefins to esters. 49 On the basis of our recent investigations and our passionate interest in carbon-supported metal−nitrogen catalyst systems, we further explore the synthesis and application of novel carbon-supported iron−nitrogen catalyst systems for selective organic transformations.…”