A polynuclear complex, {[Cu(bpe)2](NO3)}, with interpenetrated diamondoid networks: synthesis, properties and catalytic behavior

Abstract

A polynuclear complex {[Cu(bpe)2](NO3)} (1), with five-fold interpenetrated diamondoid nets, was synthesized following a hydrothermal procedure, starting from a copper(II) salt, Cu(NO3)2·2.5H2O, and using a molar ratio Cu(NO3)2 : monoethanolamine : bpe : H2O of 1 : 3 : 1 : 500. The well stirred mixture was introduced into a Teflon-lined stainless steel autoclave, heated at 423 K, and kept at this temperature for 3 days. Red single crystals containing complex 1 were fully characterized by chemical analysis, FTIR, single-crystal X-ray diffraction, powder XRD, DR-UV-Vis, TG–heat flow analysis, sorption isotherms of N2 at 77 K, and X-ray photoelectron spectroscopy (XPS). The characterization results indicated that these crystals corresponded to a copper–organic network with a microporous-like structure in which part of the channels are blocked by water molecules and nitrate ions. The synthesis led to a structure in which all the Cu ions were well stabilized as a Cu(I) species, although the precursor was a Cu(II) compound. This structure exhibits remarkable properties: high thermal stability and capacity to totally exchange NO3− anions, without causing any damage to the microporous texture. The catalytic behavior was investigated in NO decomposition and NO reduction with hexane in the presence of O2, revealing very interesting and high catalytic activity. Cu was well preserved in a Cu(I) state after the catalytic tests, which provided new information about the mechanism of NO reaction on copper.