Microporous Nanotubes and Nanospheres with Iron-Catechol Sites: Efficient Lewis Acid Catalyst and Support for Ag Nanoparticles in CO2 Fixation Reaction.

Abstract

FeIII -containing hyper-crosslinked microporous nanotubes (FeNTs) and nanospheres (FeNSs) are synthesized through the reaction of catechol and dimethoxymethane in the presence of FeCl3 or CF3 SO3 H. Both FeNTs and FeNSs demonstrate excellent catalytic activity in Lewis acid catalysis (hydrolysis and regioselective methanolysis of styrene oxide) and tandem catalysis involving a sequential oxidation-cyclization process, which selectively converts benzyl alcohol to 2-phenyl benzimidazole. Apart from Lewis acidity, the FeNTs and FeNSs also showed CO2 uptake capacities of 2.6 and 2.2 mmol g-1 , respectively, at a pressure of 1 atm and temperature of 273 K. Furthermore, Ag nanoparticles are immobilized successfully on the surfaces of FeNTs and FeNSs by the liquid-phase impregnation method to prepare Ag@FeNT and Ag@FeNS nanocomposites, which show high catalytic activity for the selective fixation of CO2 to phenylacetylene to yield phenylpropiolic acid at 60 °C and 1 atm CO2 pressure. Hence, FeIII -catechol-containing hyper-crosslinked nanotubes and nanospheres have huge potential not only as Lewis acid catalysts, but also as excellent supports for immobilizing Ag nanoparticles in the design of a robust catalyst for the carboxylation of terminal alkynes, which has wide scope in catalysis and environmental research.