A Cu(ii) MOF with a flexible bifunctionalised terpyridine as an efficient catalyst for the single-pot hydrocarboxylation of cyclohexane to carboxylic acid in water/ionic liquid medium

Abstract

The copper(II) metal–organic framework (MOF) [Cu(η-1κN,N′,N′′:2κO,O′-L)(NO₃)]_n (1) [L = 4-((4-([2,2′:6′,2′′-terpyridin]-4′-yl)benzyl)oxy)benzoate] has been synthesized from a flexible bifunctionalised terpyridine species (HL). It was characterized by elemental, FT-IR, powder and single crystal X-ray diffraction analyses. Single crystal X-ray crystallography of 1 shows a 1D polymeric architecture, whose topological analysis illustrates a uninodal (2)-connected net having topological type 2C1. 1 shows good catalytic activity and selectivity towards the hydrocarboxylation of cyclohexane to cyclohexanecarboxylic acid in water/acetonitrile or water/ionic liquid [BMPyr][NTf₂] [BMPyr = 1-butyl-1 methylpyrrolidinium; NTf₂ = bis(trifluoromethanesulfonyl)imide] medium. It can be recycled and reused without any significant loss of catalytic efficiency. This study provides the first example of an efficient alkane hydrocarboxylation to carboxylic acid, in an ionic liquid and under mild conditions.