School of Chemistry, University of Hyderabad, Hyderabad, 500 046, India.
Chemistry. 2010 Dec 27;16(48):14378-84. doi: 10.1002/chem.201001679.
Achieving a harmonious combination of the efficiency of homogeneous catalysts with the reusability of heterogeneous catalysts is a fundamental and challenging problem. Metal nanoparticles in a suitable matrix offer a potential solution. However an ideal design is yet to be realized, because the critical requirements of facile access to the catalyst, its durability, and ease of retrieval and reuse are difficult to reconcile. We report herein a multilayer free-standing thin-film catalyst based on silver nanoparticles, generated in situ inside poly(vinyl alcohol) by using a facile protocol, which shows excellent efficiency and extensive reusability in the prototypical reaction, the reduction of 4-nitrophenol by sodium borohydride. The "dip catalyst" film, which can start/stop the reaction instantaneously by mere insertion/removal, is used 30 times leading to a total turnover number (TON) of ≈3390, which is unprecedented for this reaction. The efficiency of the catalyst is reduced only marginally at the end of these runs, promising further extended usage. The unique advantage of convenient catalyst monitoring is illustrated by the periodic spectroscopic and microscopic examinations of the thin film, which revealed the basis of its durability. The demonstrated potential of metal-nanoparticle-embedded polymer thin films, coupled with their versatility and ease of fabrication, promises extensive applications in chemical catalysis.
实现均相催化剂的效率与多相催化剂的可重复使用性的和谐结合是一个基本且具有挑战性的问题。合适基质中的金属纳米粒子提供了一种潜在的解决方案。然而，理想的设计尚未实现，因为催化剂的便捷获取、耐久性以及易于回收和再利用的关键要求难以协调。我们在此报告了一种基于银纳米粒子的多层独立式薄膜催化剂，它是通过使用简单的方案在聚乙烯醇中就地生成的，在典型反应（硼氢化钠还原 4-硝基苯酚）中表现出优异的效率和广泛的可重复使用性。“浸渍催化剂”薄膜可以通过简单的插入/取出来即时启动/停止反应，使用 30 次后总转化数（TON）约为 3390，这对于该反应来说是前所未有的。在这些运行结束时，催化剂的效率仅略有降低，有望进一步延长使用时间。通过对薄膜进行定期的光谱和微观检查，说明了方便催化剂监测的独特优势，揭示了其耐用性的基础。嵌入金属纳米粒子的聚合物薄膜的潜力，加上其多功能性和易于制造，有望在化学催化中得到广泛应用。
