2,2,6,6-Tetramethylpiperidinium-nitroxide (TEMPO) is a mild and efficient catalyst, which is important in the industrial production of selective oxidation of alcohols to the corresponding aldehyde or ketone compounds. However, it is a challenge to recover the expensive TEMPO catalyst in homogeneous catalytic systems. In this study, a novel polymer-supported catalyst was prepared using 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxy (4-OH-TEMPO) and polyaromatic ether sulfone (PAES). The successful grafting of 4-OH-TEMPO in PAES-C was demonstrated by 1 H nuclear magnetic resonance ( 1 H NMR) and Fourier transform infrared (FT-IR), load capacity can be calculated by elemental analysis (EA). BET and scanning electron microscopy (SEM) to depict the structure-performance relationship. Herein, SEM images revealed the existence of porous structure. This structure can effectively adsorb NO molecules to form a PAES-TEMPO/NO x catalytic system to selectively oxidize benzyl alcohol. The experimental results indicated the high activity, the subsequent benzyl alcohol oxidation cycle can reach more than 93% conversion without showing a large loss of selectivity. More importantly, the as-prepared catalyst exhibited the attractive recyclability (recovery rate is 98%). After 10 consecutive runs, no significant loss of conversion and selectivity was observed (the conversion rate of benzyl alcohol was more than 93% and the selectivity was more than 95%). This study might provide some recommendation on the development of highly efficient catalysts for alcohol oxidation.
Bei Jiang,Mengya Xu,Ling Zhang,Wenjing Wang,Xin Qin,Shenyan Xu,Chunyu Che,Chuanqi Zhang,Wenzhong Wang
Open-shell organic radicals, characterized by their unique spin states, typically exhibit exceptional photothermal conversion efficiency. However, the development of open-shell organic radical materials with stability and high photothermal properties remains a challenge. Among these radicals, the stable and commercialized 4-OH-TEMPO radical molecule has garnered considerable attention in various organic synthesis reactions owing to its unique redox advantages, but it shows less application comparing with the other open-shell organic radicals in photo-thermal conversion. In this study, 4-OH-TEMPO exhibits favorable photothermal properties upon combination with Cu 2 + , thus it is capable of enhancing the reaction rate of HMF oxidation to DFF by a factor of 10 under LED (400 nm). Under illumination of LED, leading to the complete conversion of HMF and the generation of DFF with a yield of 99.7 % within 30 min. Mechanism study shows that the photothermal effect facilitates the kinetic process of the reaction, and accelerated conversion of 4-OH-TEMPO to the oxidatively active species 4-OH-TEMPO + under light-induced action further increased the reaction rate. This research proffers novel insights and references for 4-OH-TEMPO mediated organic synthesis reactions and the design of free-radical photothermal materials.
Shidong Song,Junjie Ma,Huanlei Zhao,Phumlani F. Msomi,Jiahao Ren,Yanan Liu,Run Ma,Wanyu Ye
In terms of stability and safety, quasi-solid-state lithium-oxygen batteries (QSSLOBs) outperform traditional liquid LOBs. However, using redox mediators (RMs) in QSSLOBs requires unique strategy to inhibit the shuttle effect of RMs. In this work, a PEO-based oxygen electrode with anchored 4-OH-TEMPO (4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy) RM (referred to as TEMPO-PEO) is developed via hydrogen-bonding interaction for QSSLOBs. The TEMPO-PEO oxygen electrode can perform both significant mediation function and oxygen reduction reaction (ORR) activity. The QSSLOB using TEMPO-PEO electrode achieves a low discharge/charge voltage gap of 0.9 V and a high Coulombic efficiency of 96.8 %, which is significantly superior to the counterparts using TEMPO solution (TEMPO cell) or unanchored TEMPO (TEMPO+PEO cell). On this basis, the TEMPO-PEO cell achieves an unprecedented cycle performance for 320 cycles under the limited capacity of 300 mAh g −1 , overwhelmingly outperforming the counterpart cells that only deliver 63 cycles (TEMPO cell) and 119 cycles (TEMPO+PEO cell), respectively. After cycling, the TEMPO RM can still be well retained on TEMPO-PEO oxygen electrode and no significant side product is formed on the after-cycled Li anode of TEMPO-PEO cell, explicitly demonstrating a strong and consistent anchoring effect on suppressing the shuttling of RM species.
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