Novel microporous rhodium(II) carboxylate polymer complexes containing metalloporphyrin: syntheses and catalytic performances in hydrogenation of olefins

Abstract

Novel microporous rhodium(II) carboxylate polymer complexes containing metalloporphyrin, Rh 2[MTCPP] (M = H 2 1, Cu 2+ 2, Ni 2+ 3, Pd 2+ 4) (H 2TCPP = 4,4′,4″,4′″-(21 H,23 H-porphine-5,10,15,20-tetrayl)tetrakis benzoic acid), were synthesized and completely characterized by elemental analysis, TG/DTA, magnetic susceptibilities, FT-IR, DR-UV–vis, XRPD, BET analysis, and nitrogen adsorption measurements. These complexes possess carboxylate bridged dinuclear rhodium(II) sites and mononuclear copper(II), nickel(II), and palladium(II) centers in the porphyrin ring that form uniform micropores of ca. 5.0 Å. Furthermore, they show high surface areas and high nitrogen adsorption capacities and act as efficient heterogeneous catalysts for the hydrogenation of olefins at approximately 200 K. The unique bimetallic effects shown by metalloporphyrin and dinuclear rhodium sites in micropores were investigated by kinetic studies and hydrogen and propene adsorption–desorption measurements; the priority coordination of olefins onto metalloporphyrins and the intramolecular transfer of hydrogen from a rhodium center to a olefin molecule coordinated onto metalloporphyrin remarkably reflects the catalytic activities in hydrogenation.