Tan Kai-Jher, Morikawa Satoshi, Ozbek Nil, Lenz Magdalena, Arlt Carsten-René, Tschöpe André, Franzreb Matthias, Hatton T Alan
Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States of America.
Department of Chemical Engineering, Faculty of Chemical and Metallurgical Engineering, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey.
Langmuir. 2023 Feb 28;39(8):2943-2956. doi: 10.1021/acs.langmuir.2c02674. Epub 2023 Feb 16.
A framework of ferrocene-containing polymers bearing adjustable pH- and redox-active properties in aqueous electrolyte environments was developed. The electroactive metallopolymers were designed to possess enhanced hydrophilicity compared to the vinylferrocene (VFc) homopolymer, poly(vinylferrocene) (PVFc), by virtue of the comonomer incorporated into the macromolecule, and could also be prepared as conductive nanoporous carbon nanotube (CNT) composites that offered a variety of different redox potentials spanning a ca. 300 mV range. The presence of charged non-redox-active moieties such as methacrylate (MA) in the polymeric structure endowed it with acid dissociation properties that interacted synergistically with the redox activity of the ferrocene moieties to impart pH-dependent electrochemical behavior to the overall polymer, which was subsequently studied and compared to several Nernstian relationships in both homogeneous and heterogeneous configurations. This zwitterionic characteristic was leveraged for the enhanced electrochemical separation of several transition metal oxyanions using a P(VFc--MA)-CNT polyelectrolyte electrode, which yielded an almost twofold preference for chromium as hydrogen chromate versus its chromate form, and also exemplified the electrochemically mediated and innately reversible nature of the separation process through the capture and release of vanadium oxyanions. These investigations into pH-sensitive redox-active materials provide insight for future developments in stimuli-responsive molecular recognition, with extendibility to areas such as electrochemical sensing and selective separation for water purification.
开发了一种在水性电解质环境中具有可调节pH和氧化还原活性的含二茂铁聚合物框架。与乙烯基二茂铁（VFc）均聚物聚（乙烯基二茂铁）（PVFc）相比，通过将共聚单体引入大分子中，设计出的电活性金属聚合物具有增强的亲水性，并且还可以制备成导电纳米多孔碳纳米管（CNT）复合材料，该复合材料提供了约300 mV范围内的各种不同氧化还原电位。聚合物结构中带电的非氧化还原活性部分（如甲基丙烯酸酯（MA））的存在赋予其酸解离特性，该特性与二茂铁部分的氧化还原活性协同相互作用，赋予整个聚合物pH依赖的电化学行为，随后对其进行了研究，并与均相和异相配置中的几种能斯特关系进行了比较。利用这种两性离子特性，使用P（VFc-MA）-CNT聚电解质电极增强了几种过渡金属氧阴离子的电化学分离，该电极对铬酸氢根形式的铬的偏好几乎是其铬酸根形式的两倍，并且还通过钒氧阴离子的捕获和释放例证了分离过程的电化学介导和固有可逆性质。这些对pH敏感的氧化还原活性材料的研究为刺激响应分子识别的未来发展提供了见解，并可扩展到电化学传感和水净化选择性分离等领域。
