Synergistic Catalysis of Brønsted Acid and Lewis Acid Coexisted on Ordered Mesoporous Resin for One-Pot Conversion of Glucose to 5-Hydroxymethylfurfural

Solvation Structure Regulation for Highly Reversible Aqueous Al Metal Batteries

Metallic Al has been deemed an ideal electrode material for aqueous batteries by virtue of its abundance and high theoretical capacity (8056 mAh cm-3). However, the development of aqueous Al metal batteries has been hindered by several side reactions, including water decomposition, Al corrosion, and passivation, which arise from the solvation reaction of Al and H2O in conventional aqueous electrolytes. In this work, we report that water activity in electrolyte can be suppressed by optimizing the Al3+ solvation structure through intercalation of polar pyridine-3-carboxylic acid in an aluminum trifluoromethanesulfonate aqueous environment. Furthermore, the pyridine-3-carboxylic acid molecules are inclined to alter the surface energy of Al, thus suppressing the random deposition of Al. As a result, the Al corrosion in the hybrid electrolyte is restrained, and the long-term electrochemical stability of the electrolyte is tremendously improved. These merits bring remarkable reversibility to aqueous Al batteries using Al-preintercalated MnO2 cathodes, delivering a retaining energy density of >250 Wh kg-1 at 0.2 A g-1 after 600 cycles.

Cooperative Catalysis Mechanism of Brønsted and Lewis Acids from Al(OTf)3 with Methanol for β-Cellobiose-to-Fructose Conversion: An Experimental and Theoretical Study

Al-containing catalysts, e.g., Al(OTf)3, show good catalytic performance toward the conversion of cellulose to fructose in methanol solution. Here, we report the catalytic isomerization and alcoholysis mechanisms for the conversion of cellobiose to fructose at the PBE0/6-311++G(d,p), aug-cc-pVTZ theoretical level, combining the relevant experimental verifications of electrospray ionization mass spectrometry (ESI-MS), high-performance liquid chromatography (HPLC), and the attenuated total reflection-infrared (ATR-IR) spectra. From the alcoholysis of Al(OTf)3 in methanol solution, the catalytically active species involves both the [CH3OH2]+ Brønsted acid and the [Al(CH3O)(OTf)(CH3OH)4]+ Lewis acid. There are two reaction pathways, i.e., one through glucose (glycosidic bond cleavage followed by isomerization, w-G) and another through cellobiulose (isomerization followed by glycosidic bond cleavage, w-L). The Lewis acid ([Al(CH3O)(OTf)(CH3OH)4]+) is responsible for the aldose-ketose tautomerization, while the Brønsted acid ([CH3OH2]+) is in charge of ring-opening, ring-closure, and glycosidic bond cleavage. For both w-G and w-L, the rate-determining steps are related to the intramolecular [1,2]-H shift between C1-C2 for the aldose-ketose tautomerization catalyzed by the [Al(CH3O)(OTf)(CH3OH)4]+ species. The Lewis acid ([Al(CH3O)(OTf)(CH3OH)4]+) exhibits higher catalytic activity toward the aldose-ketose tautomerization of glycosyl-chain-glucose to glycosyl-chain-fructose than that of chain-glucose to chain-fructose. Besides, the Brønsted acid ([CH3OH2]+) shows higher catalytic activity toward the glycosidic bond cleavage of cellobiulose than that of cellobiose. Kinetically, the w-L pathway is predominant, whereas the w-G pathway is minor. The theoretically proposed mechanism has been experimentally testified. These insights may advance on the novel design of the catalytic system toward the conversion of cellulose to fructose.