Synthesis of layered organic–inorganic nanohybrid zinc–aluminium-2-(4-chlorophenoxy)-2-methyl propionic acid with controlled release properties

A plant growth regulator, 2-(4-chlorophenoxy)-2-methyl propionic acid (CFA), was successfully intercalated into zinc–aluminium layered double hydroxide (ZAL) forming a new nanohybrid composite, zinc–aluminium-2-(4-chlorophenoxy)-2-methylpropionate layered double hydroxide (ZAC). Well-crystallized nanohybrid composite was obtained when the material was synthesized with zinc to aluminium molar ratio, R = 4 and 0.2 M CFA. Due to the intercalation of CFA, basal spacing expanded from 8.9 Å in the ZAL to 21.4 Å in the ZAC. The FTIR spectra of the ZAC nanohybrid composite show resemblance peaks of the ZAL and CFA indicating the inclusion of the organic compound into the LDH interlamellae. The loading percentage of CFA is 40.0% (w/w) calculated based on the percentage of carbon in the sample. The BET surface area increased from 1.0 to 70.0 m² g⁻¹ due to the inclusion of CFA into the ZAL interlamellae and associated expansion of the layered structure. Release of CFA from the ZAL interlayer was found to be dependent on the affinity of the incoming anion, in the order of phosphate > sulfate > nitrate with the percentage saturated release of 74, 54, and 42%, respectively. This study indicates the potential application of zinc–aluminium-layered double hydroxide as a host for plant growth regulator, CFA, with controlled release capability.