Nanoporous Copper Metal Catalyst in Click Chemistry: Nanoporosity‐Dependent Activity without Supports and Bases

Abstract

Nanoporous copper (CuNPore) catalysts with tunable nanoporosity were fabricated from Cu 30 Mn 70 alloy by controlling the de-alloying temperature under free corrosion conditions. The tunable nanoporosity of CuNPore led to a significant enhancement of catalytic activity in click chemistry without using any supports and bases. Characterization of CuNPore surface, high reusability, leaching experiment, and formation of nanostructured copper acetylide revealed that the click reaction occurred at the catalyst surface.Keywords: click reaction; heterogeneous catalysis; high reusability; nanoporous copper catalyst; tunable nanoporosity Nanoporous metals are promising materials for catalysis, [1][2][3] sensing, [4] and actuation [5] applications due to their interesting structural, optical and surface properties. In spite of the growing number of studies on various applications of nanoporous metals, the catalytic properties in chemical reactions are still less explored, although the interesting features of nanoporous metals make them potentially attractive candidates for new heterogeneous catalysts; [1][2][3] the three-dimensional, open-pore network structures and metal ligaments allow the transport of molecules and ions, a high surface-to-volume ratio in comparison with bulk metals results in outstanding catalytic efficiency; furthermore, the potentially high reusability and rather simple work-up are favorable for practical synthetic methodology. Moreover, in contrast to the supported nanoparticles (NPs) catalyst, a nanoporous metal without supports should be a challenging catalyst system to understand the relevant catalytic mechanism more easily and to extend the catalytic application widely by elimination of the support effect problems and relaxation of aggregation. In this regard, we have focused on the study of the catalytic properties of unsupported nanoporous metals in organic molecular transformations under liquid-phase conditions.

Catalytic Performance of Nanoporous Metal Skeleton Catalysts for Molecular Transformations

“…It was interesting that the ligament size of CuNPore influenced significantly the catalytic activity in the CuACC reaction of phenylacetylene 7 a and benzyl azide 35 a in toluene at 65 °C (Scheme ) . For example, almost quantitative yield of the corresponding 1,2,3‐triazole product 36 a was obtained using the CuNPore‐2 catalyst with a ligament size of 40 nm, which was much higher than when CuNPore‐1 with a small ligament size of 30 nm was used.…”

“…A wide range of terminal alkynes and organic azides can be employed in the CuNPore‐2‐catalyzed CuACC reaction. Not only aromatic and heteroaromatic alkynes but also aliphatic alkynes were reacted with various organic azides to afford the corresponding 1,2,3‐triazoles 36 in excellent yields (Scheme ) . Interestingly, we found that nanostructured polymeric Cu acetylide was formed on the CuNPore surface when mixing phenylacetylene with CuNPore‐2 in toluene, which was considered to be a key catalytic species in CuACC reaction.…”

Oxidation of Organosilanes with Nanoporous Copper as a Sustainable Non‐Noble‐Metal Catalyst

“…Related nanoporous non‐noble‐metal catalyzed reactions are rare. Only Jin et al have reported nanoporous copper (np‐Cu)‐catalyzed click chemistry, which showed high yield and selectivity 14. In addition, other porous Cu‐based catalysts have also shown high activity in organic reactions 15.…”

Mixing Time of Molecules Inside of Nanoporous Gold

“…AuNP is formed by treating a goldsilver alloy with concentrated acid, which removes the silver component of the alloy and leaves a bicontinuous structure of gold and a disordered network of pores [3,4,5]. The diameter of the pores can be tuned from 100 nm down to around 5 nm by adjusting the temperature and duration of the acid treatment [6,7,8]. It has recently been found that AuNP is a highly active catalyst for a variety of chemical reactions, including carbon monoxide oxidation and several important organic reactions [9,10,11].…”