Győri Enikő, Kecskeméti Ádám, Fábián István, Szarka Máté, Lázár István
Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary.
MTA-DE Redox and Homogeneous Catalytic Reaction Mechanisms Research Group, University of Debrecen, Debrecen Egyetem tér 1, H-4032 Debrecen, Hungary.
Gels. 2022 Mar 23;8(4):202. doi: 10.3390/gels8040202.
Fenton reactions with metal complexes of substituted porphyrins and hydrogen peroxide are useful tools for the mineralization of environmentally dangerous substances. In the homogeneous phase, autooxidation of the prophyrin ring may also occur. Covalent binding of porphyrins to a solid support may increase the lifetime of the catalysts and might change its activity. In this study, highly water-insoluble copper and iron complexes of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin were synthesized and bonded covalently to a very hydrophilic silica aerogel matrix prepared by co-gelation of the propyl triethoxysilyl-functionalized porphyrin complex precursors with tetramethoxysilane, followed by a supercritical carbon dioxide drying. In contrast to the insoluble nature of the porphyrin complexes, the as-prepared aerogel catalysts were highly compatible with the aqueous phase. Their catalytic activities were tested in the mineralization reaction of phenol, 3-chlorophenol, and 2,4-dichlorophenol with hydrogen peroxide. The results show that both aerogels catalyzed the oxidation of phenol and chlorophenols to harmless short-chained carboxylic acids under neutral conditions. In batch experiments, and also in a miniature continuous-flow tubular reactor, the aerogel catalysts gradually reduced their activity, due to the slow oxidation of the porphyrin ring. However, the rate and extent of the degradation was moderate and did not exclude the possibility that the as-prepared catalysts, as well as their more stable derivatives, might find practical applications in environment protection.
取代卟啉的金属配合物与过氧化氢的芬顿反应是矿化环境有害物质的有用工具。在均相中，卟啉环也可能发生自氧化。卟啉与固体载体的共价结合可能会延长催化剂的寿命，并可能改变其活性。在本研究中，合成了5,10,15,20-四（4-氨基苯基）卟啉的高度水不溶性铜和铁配合物，并将其共价键合到一种非常亲水的二氧化硅气凝胶基质上，该基质是通过丙基三乙氧基硅烷基官能化的卟啉配合物前体与四甲氧基硅烷共凝胶化制备的，随后进行超临界二氧化碳干燥。与卟啉配合物的不溶性不同，所制备的气凝胶催化剂与水相具有高度相容性。在苯酚、3-氯苯酚和2,4-二氯苯酚与过氧化氢的矿化反应中测试了它们的催化活性。结果表明，两种气凝胶在中性条件下均能将苯酚和氯苯酚氧化为无害的短链羧酸。在间歇实验以及微型连续流管式反应器中，由于卟啉环的缓慢氧化，气凝胶催化剂的活性逐渐降低。然而，降解的速率和程度适中，并不排除所制备的催化剂及其更稳定的衍生物可能在环境保护中找到实际应用的可能性。
