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Fe(III) Protoporphyrin IX Encapsulated in a Zinc Metal–Organic Framework Shows Dramatically Enhanced Peroxidatic Activity
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2018-01-08 00:00:00 , DOI: 10.1021/acs.inorgchem.7b02612
Nicola A. Dare 1 , Lee Brammer 2 , Susan A. Bourne 1 , Timothy J. Egan 1
Affiliation  

Two MOFs, [H2N(CH3)2][Zn3(TATB)2(HCOO)]·HN(CH3)2·DMF·6H2O (1) and Zn-HKUST-1 (2), were investigated as potential hosts to encapsulate Fe(III) heme (Fe(III) protoporphyrin IX = Fe(III)PPIX). Methyl orange (MO) adsorption was used as an initial model for substrate uptake. MOF 1 showed good adsorption of MO (10.3 ± 0.8 mg g–1) which could undergo in situ protonation upon exposure to aqueous HCl vapor. By contrast, MO uptake by 2 was much lower (2 ± 1 mg g–1), and PXRD indicated that structural instability on exposure to water was the likely cause. Two methods for Fe(III)PPIX-1 preparation were investigated: soaking and encapsulation. Encapsulation was verified by SEM-EDS and showed comparable concentrations of Fe(III)PPIX on exposed interior surfaces and on the original surface of fractured crystals. SEM-EDS results were consistent with ICP-OES data on bulk material (1.2 ± 0.1 mass % Fe). PXRD data showed that the framework in 1 was unchanged after encapsulation of Fe(III)PPIX. MO adsorption (5.8 ± 1.2 mg g–1) by Fe(III)PPIX-1 confirmed there is space for substrate diffusion into the framework, while the UV–vis spectrum of solubilized crystals confirmed that Fe(III)PPIX retained its integrity. A solid-state UV–vis spectrum of Fe(III)PPIX-1 indicated that Fe(III)PPIX was not in a μ-oxo dimeric form. Although single-crystal XRD data did not allow for full refinement of the encapsulated Fe(III)PPIX molecule owing to disorder of the metalloporphyrin, the Fe atom and pyrrole N atoms were located, enabling rigid-body modeling of the porphine core. Reaction of 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) with H2O2, catalyzed by Fe(III)PPIX-1 and -2, showed that Fe(III)PPIX-1 is significantly more efficient than Fe(III)PPIX-2 and is superior to solid Fe(III)PPIX-Cl. Fe(III)PPIX-1 was used to catalyze the oxidation of hydroquinone, thymol, benzyl alcohol, and phenyl ethanol by tert-butyl-hydroperoxide with t1/2 values that increase with increasing substrate molecular volume.

中文翻译:

Fe(III)原卟啉IX封装在锌金属-有机框架中显示出显着增强的过氧化活性

两个MOF,[H 2 N(CH 32 ] [Zn 3(TATB)2(HCOO)]·HN(CH 32 ·DMF·6H 2 O(1)和Zn-HKUST-1(2),被调查为潜在的宿主来封装Fe(III)血红素(Fe(III)原卟啉IX = Fe(III)PPIX)。甲基橙(MO)吸附用作底物吸收的初始模型。MOF 1显示出对MO的良好吸附(10.3±0.8 mg g –1),当暴露于HCl水溶液中时,MO可以原位质子化。与此相反,MO摄取2低得多(2±1毫克克-1),PXRD表示可能是由于暴露于水引起的结构不稳定性。研究了两种制备Fe(III)PPIX- 1的方法:浸泡和包封。通过SEM-EDS验证了包封,并且在暴露的内表面和破裂的晶体的原始表面上显示出相当浓度的Fe(III)PPIX。SEM-EDS结果与散装材料(1.2±0.1质量%Fe)上的ICP-OES数据一致。PXRD数据表明,Fe(III)PPIX包封后1中的骨架没有变化。Fe(III)PPIX- 1的MO吸附(5.8±1.2 mg g –1证实有底物扩散到框架中的空间,而可溶晶体的UV-vis光谱证实Fe(III)PPIX保持其完整性。Fe(III)PPIX- 1的固态紫外-可见光谱表明,Fe(III)PPIX不是μ-氧代二聚体形式。尽管由于金属卟啉的无序性,单晶XRD数据无法完全精炼所包封的Fe(III)PPIX分子,但仍定位了Fe原子和吡咯N原子,从而可以对卟啉核心进行刚性建模。Fe(III)PPIX- 1-2催化2,2'-叠氮基双(3-乙基苯并噻唑啉)-6-磺酸(ABTS)与H 2 O 2反应,表明Fe(III)PPIX- 1个与Fe(III)PPIX- 2相比效率更高,并且优于固态Fe(III)PPIX-Cl。Fe(III)PPIX- 1用于催化丁基氢过氧化氢对苯二酚,百里酚,苯甲醇和苯乙醇的氧化,t 1/2值随底物分子体积的增加而增加。
更新日期:2018-01-08
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