PdS修饰的ZnIn_(2)S_(4)复合材料用于可见光催化硫醇偶联制备二硫化物同时产氢

Visible light‐driven dehydrocoupling of thiols to disulfides and H_(2) evolution over PdS-decorated ZnIn_(2)S_(4) composites

二硫化物及其衍生物是生物、医药和工业合成的重要中间体,不仅在蛋白质功能化和药物传递系统中发挥着重要作用,而且在橡胶硫化剂、农药和抗氧化剂的生产中广泛应用.在传统合成策略中,有毒或昂贵的试剂通常被用于硫醇的偶联,且该过程存在反应条件苛刻、选择性低和反应时间长等问题.相比之下,光催化技术能够通过S-S偶联,将硫醇选择性地转化为二硫化物同时产氢,构建一种由光催化析氢和选择性有机合成相结合的光氧化还原体系.该双功能光催化反应体系能够充分利用光生电子和空穴的能量,同时获得绿色的清洁燃料和高价值的精细化学品,从而满足经济和社会可持续发展的目标.本文采用简便的水热法和原位沉积法成功合成了PdS助催化剂修饰的ZnIn_(2)S_(4)复合光催化剂.在可见光照射下,二元PdS-ZnIn_(2)S_(4)复合材料可以高效地催化硫醇进行选择性脱氢偶联,充分利用高能电子和空穴,同时获得清洁的氢能源以及增值的二硫化物.研究表明,PdS作为一种高效的氧化型助催化剂,不仅可以有效地从ZnIn_(2)S_(4)半导体中捕获光生空穴,促进光生载流子的分离和转移,而且能作为硫醇氧化的活性反应位点,从而显著提高ZnIn_(2)S_(4)的光催化性能.3%PdS-ZnIn_(2)S_(4)复合材料具备最佳的光催化活性,其双(4-甲氧基苯基)二硫化物和氢气的产量分别是ZnIn_(2)S_(4)的8.4和10.7倍.此外,二硫化物在该光催化反应过程中表现出优异的选择性(>99.0%).循环活性实验以及催化反应前后的X射线光电子能谱结果表明,二元PdS-ZnIn_(2)S_(4)复合材料具有良好的光催化稳定性.PdS-ZnIn_(2)S_(4)可以有效地催化多种具有不同取代基的硫醇的脱氢偶联,生成相应的S-S目标产物,说明了二元PdS-ZnIn_(2)S_(4)复合材料在光催化硫醇转化中的普适性.此外,原位傅里叶变换红外光谱揭示了反应物在催化剂表面的动态变化.通过电子顺磁共振光谱技术对反应过程中的自由基中间体进行原位监测,确认了硫中心自由基是硫醇氧化偶联过程中关键的自由基中间体.综上,本文为以绿色可持续的方式同时获得清洁太阳能燃料和具有高附加值的化学品提供了参考.

The simultaneous utilization of photogenerated electrons and holes in one cooperative photoredox system for the dehydrocoupling of thiols into value-added disulfides and clean hydrogen(H_(2))fuel meets the development criteria of green chemistry.Herein,we report the synthesis and application of cocatalyst PdS decorated ZnIn_(2)S_(4)(PdS-ZIS)composites for photocatalytic coupling of thiols into disulfides and H2 evolution under visible light irradiation.The superior photocatalytic performance over PdS-ZIS composites compared with blank ZIS is attributed to the function of PdS as oxidation cocatalyst,which dramatically promotes the separation and transfer of photogenerated charge carriers due to its excellent hole trapping ability.In-situ Fourier transform infrared spectra reveal the dynamic variation of reactants on the catalyst surface.Electron paramagnetic resonance technology confirms that sulfur-centered radicals are the key reaction intermediates in this coupling process.Moreover,the application of PdS-ZIS composites to the dehydrocoupling of various thiols with different substituent groups into the corresponding S-S coupling products has been demonstrated to be practicable.This work is expected to offer insights into the rational design of cocatalyst-decorated semiconductor photocatalysts with efficient utilization of photogenerated electrons and holes for the co-production of high-value chemicals and clean H2 energy in a cooperative photoredox catalysis process.