Solvothermal Preparation of an Electrocatalytic Metalloporphyrin MOF Thin Film and its Redox Hopping Charge-Transfer Mechanism
Solvothermal Preparation of an Electrocatalytic Metalloporphyrin MOF Thin Film and its Redox Hopping Charge-Transfer Mechanism
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DOI：
10.1021/ja410684q
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发表时间：
2014-02-12
影响因子：
15
通讯作者：
Morris, Amanda J.
中科院分区：
文献类型：
--
作者：
Ahrenholtz, Spencer R.;Epley, Charity C.;Morris, Amanda J.
用溶剂热法在导电的掺氟氧化锡基底上制备了由[5，10，15，20-（4-羧基苯基）卟啉]Co（III）（CoTCPP）骨架和线性三核Co-II-羧酸簇合物构成的金属卟啉金属有机骨架薄膜。这种介孔薄膜材料的表征，指定为CoPIZA/FTO，它配备了大的空腔和金属活性位点的访问，揭示了一种电化学活性材料。循环伏安法显示在-1.04 V处相对于亚铁氰化物的E-1/2可逆峰归因于（（CoTCPP）-T-III/II）CoPIZA氧化还原对，并且在-1.45 V处相对于亚铁氰化物的准可逆峰对应于（（CoTCPP）-T-II/I）CoPIZA的还原。对（（CoTCPP）-T-II/I）CoPIZA氧化还原对的光谱电化学响应的分析显示非能斯特还原，非理想因子为2，相对于亚铁氰化物的E-1/2为-1.39 V。该膜被证明保持其结构完整性与所施加的电位，如光谱电化学所证明的，在430，458，和544 nm处的等吸光点对应于（（CoTCPP）-T-III/II）CoPIZA过渡和在390和449 nm处的对应于（（CoTCPP）-T-II/I）CoPIZA过渡的维护。通过膜的电荷传输的机制，提出了一个氧化还原跳跃机制，这是支持的循环伏安法和光谱电化学。将时间依赖性光谱电化学数据拟合到修改的Cottrell方程，得到双极电子和阳离子在整个膜中传输的表观扩散系数为7.55（+/- 0.05）x 10（-14）cm（2）/s。在将金属卟啉支柱还原为（（CoTCPP）-T-I）CoPIZA后，CoPIZA薄膜表现出对四氯化碳还原的催化活性。
A thin film of a metalloporphyrin metal organic framework consisting of [5,10,15,20-(4-carboxyphenyl)porphyrin]Co(III) (CoTCPP) struts bound by linear trinuclear Co-II-carboxylate clusters has been prepared solvothermally on conductive fluorine-doped tin oxide substrates. Characterization of this mesoporous thin film material, designated as CoPIZA/FTO, which is equipped with large cavities and access to metal active sites, reveals an electrochemically active material. Cyclic voltammetry displays a reversible peak with E-1/2 at -1.04 V vs ferrocyanide attributed to the ((CoTCPP)-T-III/II)CoPIZA redox couple and a quasi-reversible peak at -1.45 V vs ferrocyanide, which corresponds to the reduction of ((CoTCPP)-T-II/I)CoPIZA. Analysis of the spectroelectrochemical response for the ((CoTCPP)-T-II/I)CoPIZA redox couple revealed non-Nernstian reduction with a nonideality factor of 2 and an E-1/2 of -1.39 V vs ferrocyanide. The film was shown to retain its structural integrity with applied potential, as was demonstrated spectroelectrochemically with maintenance of isosbestic points at 430, 458, and 544 nm corresponding to the ((CoTCPP)-T-III/II)CoPIZA transition and at 390 and 449 nm corresponding to the ((CoTCPP)-T-II/I)CoPIZA transition. The mechanism of charge transport through the film is proposed to be a redox hopping mechanism, which is supported by both cyclic voltammetry and spectroelectrochemistry. A fit of the time-dependent spectroelectrochemical data to a modified Cottrell equation gave an apparent diffusion coefficient of 7.55 (+/- 0.05) x 10(-14) cm(2)/s for ambipolar electron and cation transport throughout the film. Upon reduction of the metalloporphyrin struts to ((CoTCPP)-T-I)CoPIZA, the CoPIZA thin film demonstrated catalytic activity for the reduction of carbon tetrachloride.