Electrochemical and photochemical applications of multifunctional metal phosphonates

Abstract

In this PhD thesis, proton conductivity, photocatalytic and luminescence properties of synthesised multifunctional metal phosphonates have been studied. Iron and zinc derivatives of the R,S hydroxyphosphonoacetic acid (HPAA), M[HO3PCH(OH)CO2]2.5H2O, have been synthesised as well as the corresponding iron-containing bimetallic solid solutions, FexM1-x[HO3PCH(OH)CO2]2.5H2O (M= Mn2+, Co2+ and Zn2+), showing remarkable properties as proton conductors and Photo-Fenton catalyst. These layered solids exhibited NH3/H2O-mediated proton conductivity, which increases with higher amounts of these two guest species (up to 1.8·10-3 S·cm-1). Upon ammonia adsorption, solids become increasingly amorphous, but PDF studies revealed that the local Fe2+ environment was still preserved. Regarding to photocatalytic properties, Fe-HPAA and FexM1-x-HPAA (x > 0.5) are efficient photo-Fenton catalysts for the degradation of recalcitrant pollutants, such as phenol and 4-chlorophenol (~90% TOC removal) and methylene blue (75%). Transition metals and lanthanide 2-[bis(phosphonomethyl)amino]-ethanesulfonate compounds have been obtained by solvo-, hydrothermal or microwave-assisted synthesis: Mn2[(O3PCH2)2-NH-(CH2)2-SO3]·3H2O, o-Mn2HSP, Zn2[(O3PCH2)2-NH-(CH2)2-SO3]/Zn0.4[O3PCH2-NH-CH3]0.4(NH3)2·4H2O, m-Zn2HSP, Zn2[(O3PCH2)2-NH-(CH2)2-SO3]·7H2O, h-Zn2HSP, and Ln[H(O3PCH2)2-NH-(CH2)2-SO3]·2H2O, m-LaH2SP and o-LnH2SP (Ln= Pr, Nd, Sm, Eu, Gd and Tb).