Accelerating Selective Oxidation of Biomass-Based Hydroxyl Compounds with Hydrogen Bond Acceptors

Abstract

Hydrogen-bonding-initiated self-association makes the valorization of biomass-based hydroxyl compounds a formidable challenge at high concentration. Apart from enhancing the dehydration reaction of hydroxyl compounds with the noncovalent medium effects, insights into how these effects can be exploited to optimize the oxidative reactivity of concentrated hydroxyl compounds remain unclear. Herein, we elucidate that deaggregation of hydroxyl groups with a catalytic number of hydrogen bond acceptors is essential in improving the reactivity of the aerobic oxidation of biomass-based neat aromatic alcohols over the vanadium-based catalyst. The neat 5-hydroxy­methylfurfural (HMF) deaggregated with 25 mol % N,N-dimethyl­formamide (DMF) shows a >7-fold increase in reactivity to produce corresponding aldehydes with excellent selectivity, in stark contrast to the contrary deactivation of reaction in excessive DMF.

Aerobic Oxidation of 5‐Hydroxymethylfurfural via Hydrogen Bonds Reconstruction with Ternary Deep Eutectic Solvents

“…Consequently, there emerges certain scenarios where the hydrogen bonds become undesirable, particularly in the catalytic conversion of hydroxyl compounds derived from the biomass such as cellulose, lignin, and the concentrated 5-hydroxymethylfurfural (HMF). [16,33] As mentioned above, the selective oxidation of HMF using different ratios of DESs exhibited significant different reaction result both on the conversion and selectivity of oxidation products. It was believed that these variations may be related with the hydrogen bonding effect in the catalytic system, which subsequently affected the hydrogen bonding interactions between DESs and HMF.…”

Deep eutectic solvents coupled with (NH4)3H6CoMo6O24trigger aerobic oxidation of 5-hydroxymethylfurfural to 5-formyl-2-furancarboxylic acid

“…In general, the intermolecular hydrogen-bonding network is undesirable for catalytic conversion because of the high tendency for self-oligomerization in concentrated HMF. 6 Therefore, disruption of the initial hydrogen bonds between HMF molecules and controllable reconstruction of new H-bonds between individual HMF molecules and DESs are the key to effective catalytic conversion. These processes can facilitate the activation of the aldehyde and hydroxyl groups and drive the desorption of oxidative products from the catalyst during HMF oxidation.…”

“…[1][2][3][4] Biomass can be refined and processed to produce a variety of high-value-added products. [5][6][7] Notably, 5-hydroxymethylfurfural (HMF), a valuable and readily available compound, is an attractive platform molecule containing aldehyde and hydroxyl groups. This compound is formed by the continuous dehydration of hexose and can be utilized as a biobased precursor for many industrially valuable chemicals such as 2,5-diformylfuran (DFF), 5-hydroxymethyl-2furancarboxylic acid (HMFCA), 5-formyl-2-furancarboxylic acid (FFCA), and 2,5-furandicarboxylic acid (FDCA) (Fig.…”

“…[24][25][26][27][28] Moreover, it is challenging to convert concentrated biomass-based hydroxyl compounds into high-valueadded products due to the self-association induced by initial hydrogen bonding. 6 Certain DESs can function as molecular scissors with sufficient reconstruction ability: such DESs can break initial hydrogen bonds and promote the formation of new hydrogen bonds. From this perspective, the use of DESs can facilitate HMF conversion.…”

“…This result implied that the hydrogen bonds of neat HMF were broken in DESs, leading to the depolymerization of hydroxyl and aldehyde groups. Subsequently, the H-bonds reformed between the individual HMF molecule with DESs, 6,7 resulting in the interaction between the -OH and -CHO groups of HMF with DESs, and therefore the -OH and -CHO groups will be separate by DESs and cannot occur polymerization. In general, the intermolecular hydrogenbonding network is undesirable for catalytic conversion because of the high tendency for self-oligomerization in concentrated HMF.…”