Aldehydes are valuable intermediates with widespread industrial applications, and their traditional synthesis relies on chemical oxidation that is often hazardous and environmentally unfriendly. Electrochemical oxidation offers a more sustainable and milder alternative; however, it faces challenges such as aldehyde overoxidation and susceptibility to base-catalyzed Cannizzaro disproportionation. Electrochemical glycerol oxidation to glyceraldehyde is a representative example, which typically requires precious metal-based electrocatalysts but still suffers from low selectivity and activity. Here, we report a metal-free oxidation strategy mediated by 2,2,6,6-tetramethylpiperidine-1-oxyl. By systematically investigating the redox thermodynamics and kinetics of TEMPO across a broad pH range, we construct a Pourbaix diagram and elucidate the relative kinetics of each reaction step. These insights allow us to explain the anomalously high apparent Faradaic efficiency (~200%) observed under acidic conditions, and identify neutral media as the optimal environment for selective glyceraldehyde production. Under optimized conditions, our system achieves a glyceraldehyde Faradaic efficiency exceeding 93% and a partial current density of 23.3 mA cm –2 at 0.57 V — more than doubling the performance of the best reported precious metal-based systems. Furthermore, the versatility of this strategy extends to the selective oxidation of other primary alcohols to their corresponding aldehydes with near-unity selectivity.
The nano-metal oxide-catalyzed oxidation of 5-hydroxymethylfurfural (HMF) with sodium hypochlorite (NaClO) is an effective and mild technique for synthesizing 2,5-furanediformic acid (FDCA). However, the rapid and large-scale separation of nanocatalysts remains a major challenge. In this study, we developed a magnetic and recyclable copper oxide-based catalyst supported on the mechanochemically synthesized Fe3O4. Benefiting from the introduction of the Fe3O4carrier and cetyltrimethylammonium bromide (CTAB) surfactant, the CuO-CTAB/Fe3O4catalyst owns smaller CuO particle sizes, which endows it with excellent catalytic activity in the oxidation of HMF, achieving a high FDCA yield of 90.3%. Furthermore, the rapid magnetic separation of the catalyst effectively inhibits the excessive conversion of FDCA. The recovered catalyst can be reused for at least five cycles without significant loss of catalytic performance, confirming the promising application prospect of the CuO-CTAB/Fe3O4catalyst.
Despite the critical role of polybenzimidazole (PBI) in high-temperature membranes in fuel cells, its practical deployment remains hindered by inherent limitations including low molecular weight (<20 kDa), poor solution processability, and irreversible network formation upon conventional synthesis. To address these challenges, a dynamic covalent strategy was introduced, leveraging Diels–Alder (DA) chemistry for topological reconfiguration. By subjecting furan-functionalized PBI prepolymer (PBI-furan, Mn = 8.2 kDa) to bismaleimide chain extension, we achieve a fourfold increase in molecular weight (Mn = 32 kDa), yielding a reversibly crosslinked PBI-DA membrane. Compared to traditional PBI with the same molecular weight, this architecture synergistically integrates exceptional thermal stability (>450 °C onset decomposition), robust mechanical strength (tensile strength >80 MPa), suppressed phosphoric acid swelling (<10%) and elevated ionic conductivity. Crucially, the dynamic network enables cyclic reprocessability and autonomous self-healing, retaining >90% of the initial mechanical properties after three tensile cycles. Compared to static PBI networks, this system reduces irreversible chain entanglement, while maintaining performance parity. By deeply integrating dynamic covalent chemistry with PBI materials, this work not only advances the performance of high-temperature proton-exchange membranes but also establishes a novel framework for the sustainable design of green energy devices, presenting significant scientific merit and engineering application potential.
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