DOI: 10.1002/cssc.201100850 Nanoscience Makes Catalysis Greener Vivek Polshettiwar,* [a] Jean-Marie Basset,* [a] and Didier Astruc* [b] Catalysis, which provides sustainable, economical, and effi- cient ways to convert raw materials into valuable chemicals and fuels, is essential to the development of modern society. With the aim to avoid the use of volatile organic solvents, toxic reagents, hazardous, and/or harsh reaction conditions as well as challenging and time-consuming wasteful separations, greener and environmentally benign catalytic protocols have recently become more popular. In this regard, the develop- ment of nanoscience, undreamt of a century ago, has made the greening of chemistry possible. The seemingly magical properties of nanoparticles have been unknowingly utilized for centuries. Early uses of nanostruc- tured materials include the third-century Lycurgus Cup, [1] made up of dichroic glass of gold and silver nanoparticles, which makes the cup look opaque green when lit from the outside and glowing red when lit from the inside. Similar shiny and sparkling ceramic glazes, which were used in the Islamic world between the ninth and seventeenth centuries, [2] also contained various metallic nanoparticles. The qualities of “Damascus” saber blades, used from 300 BCE to 1700 CE, including their excellent strength, toughness, resistance to shattering, and the ability to remain extremely sharp, came from their construction out of carbon nanotubes and cementite nanowires. [3] We use huge varieties of nanomaterials in our daily lives, [4] and they are now being utilized in the field of catalysis. As is often said, “nature makes and chemistry reshapes.” Nanocataly- sis is becoming an important part of nanoscience. [5] Moreover, nanocatalysis bridges homogeneous catalysis, in which catalyt- ic reactions usually proceed at a single metal site from reac- tants to products, and heterogeneous catalysis, in which mi- croscopic powders are used. Even in the century-old Haber– Bosch process for ammonia synthesis, [6] iron nanoparticles were already present. [7] It also in the beginning of the twenti- eth century that Ostwald’s simple demonstration indicated the considerable increase of surface upon dividing cubes and con- sequences for surface-dependent catalysis. Nanocatalysts are extremely structure sensitive and their cata- lytic efficiency and selectivity dramatically depend on the size, shape, and composition of the nanoparticle as well as the sup- port material; as demonstrated by the largely unexpected dis- covery that gold nanoparticles smaller than 5 nm were very active catalysts even at sub-ambient temperatures. [8,9] We now know the benefit of the increased surface-to-volume ratio of nanocatalysts as well as accessibility of specific sites (e.g., steps, edges, and corners) of catalytic nanoparticles. [10, 11] The approaches to nanocatalysts are multiple and extremely varied from supported to unsupported nanocrystals of metals, metal oxides, and others. Nanocatalytic reaction mechanisms are complex and not yet well understood, [12] however, which makes this science exciting. Modern directions that take into account the greenness of the nanocatalysts [13] include magnetic nanocatalyst recovery, [14] the use of ionic liquids, the mix of metal nanoparticles [15] in core–shell bimetallic nanoparticles and alloys, the derivatiza- tion of electrodes with nanocatalysts for improved redox catal- ysis for energy-relevant applications, the encapsulation of nanoparticles in solid zeolite-type cavities, such as molecular organic frameworks, and morphologically controlled synthesis of metals and metal oxide nanoparticles with varied shapes. [16] This special issue is devoted to development of sustainable and green catalytic protocols using nanochemistry, what we call “Green Chemistry by Nanocatalysis”. The issue includes two Reviews, two Minireviews, one Communication and seven Full Papers, all of which were invited contributions by experts in the field. The first article is a Review by Ranu et al. on use of copper-based nanocatalysts for carbon–carbon and carbon– heteroatom bond formation, both of which are used extensive- ly in the chemical, material, and industrial communities. They have provided an exclusive account of the developments in this field and also their green perspective. In the next article, Garcia and co-workers provide a critical Review on the use of metal nanoparticles for the Fenton reac- tion. The generation of hydroxyl radicals from hydrogen perox- ide, known as the Fenton reaction, is one of the best ways to tackle organic pollutants, which are notorious sources of envi- ronmental pollution. They discuss a range of metal particles, both supported and unsupported, as Fenton catalysts and highlight their efficiency, stability and mechanism of action for degradation of organic pollutants. [a] Prof. V. Polshettiwar, Prof. J.-M. Basset KAUST Catalysis Centre (KCC) King Abdullah University of Science and Technology (KAUST) Thuwal 23955 (Kingdom of Saudi Arabia) E-mail : vivek.pol@kaust.edu.sa jeanmarie.basset@kaust.edu.sa [b] Prof. D. Astruc Univ. Bordeaux, ISM UMR CNRS 5255 33405 Talence Cedex (France) E-mail : d.astruc@ism.u-bordeaux1.fr Green Chemistry by Nanocatalysis 6  2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemSusChem 2012, 5, 6 – 8