固载模拟[Fe-Fe]氢化酶在纯水体系中的产氢及电子转移过程研究

The requirement to develop inexpensive renewable energy sources has stimulated new approaches to establish light-induced hydrogen production system in conversion and storage of solar energy. Hydrogen photoproduction through mimicking natural photosynthesis is considered to be one of the most attractive and potential means. Since the biological structures and the functionalities of the active sites of hydrogenases were proposed, the diiron hydrogenase modeling has shown a very blooming development in photochemical hydrogen production. However, none of these hydrogenase mimics show catalytic activities as high as natural hydrogenases do, and the effective charge separation has been considered to be a key factor in photochatalytic hydrogen evolution. The construction of robust hydrogenase models with high photocatalytic activity and efficiency remains a great challenge. Moveover, it is essential to develope a universal method to overcome their poor solubility in water. In this project, the hydrogenase mimics will be immobilized to hydrogel or molecular sieve, which will be applied in pure water for hydrogen photoproduction. The activity of the immobilized hydrogenase mimics for hydrogen evolution, and the electron transfer process will be investigated. The stabilizing effect of the supports on the hydrogenase mimics and the charge separation state will also be discussed. This project will provide a general strategy for establishing artificial hydrogen evolution systems in pure water.

模拟自然界光合作用，发展高效太阳能光催化产氢体系一直是化学家研究的重点之一。随着人们对自然界氢化酶结构解析精度的提高，氢化酶的化学模拟以及光驱动产氢成为研究的新热点。人工模拟[Fe-Fe]氢化酶的催化活性普遍较低，有效的电荷分离被认为是提高模拟氢化酶催化活性的重要因素。寻找适合的方法延长电荷分离态寿命，提高模拟氢化酶的稳定性和催化活性成为太阳能光催化制氢研究中的重要内容。此外，人工模拟氢化酶大都不溶于水，建立一种有效且通用的方法突破模拟氢化酶对有机溶剂的依赖也是非常必要的。本项目将模拟氢化酶固载到水凝胶或分子筛载体上，应用于纯水环境光催化产氢，研究载体对模拟氢化酶催化性质和光敏剂与模拟氢化酶间的电子转移过程的影响，载体对模拟氢化酶和通过电子转移生成的模拟氢化酶离子自由基中间体(电荷分离态)的稳定化作用，以及固载人工模拟氢化酶在水中光催化产氢应用，为模拟氢化酶纯水催化体系的构筑提供新的思路。

将太阳能转化为其它能源是决绝能源短缺的重要途径之一。在众多的太阳能利用和转化方式中，光催化产氢一直是人们追求的目标。通过模仿自然光合作用实现光化学产氢，被认为是最有吸引力的和发展前途的方法之一。近年来，人们合成出了一系列[2Fe2S]配合物，用于模拟天然氢化酶催化质子生成氢气。人工模拟氢化酶迅速发展，但它们大多不溶于水，只能在有机溶剂或是有机溶剂和水的混合溶剂中使用。本项目中，我们通过疏水相互作用，将疏水性的模拟氢化酶(Hy)吸附到分子筛MCM-41中，得到固载型催化剂Hy@MCM-41。Hy@MCM-41成功地应用于纯水的光催化产氢体系，表现出良好的稳定性和催化活性。随后，我们合成了含有捕光基团和催化基团的二元配合物Ps-Hy，通过离子交换，我们得到了固载型催化剂Ps-Hy@MCM-41。同非固载的Ps-Hy相比，Ps-Hy@MCM-41的催化活性提高了大约3倍，分子筛显著提高了催化剂的稳定性，进而促进了催化反应的发生。此外，我们还利用PVP水凝胶构建了催化产氢体系，模拟氢化酶固载到PVP里同样提高了稳定性和催化活性。本项目为纯水相光催化产氢体系的构建提供了一个很好的参考，为不溶性催化剂在纯水中应用提供了一个普适平台。