One of the major challenges in the circular economy relating to food packaging is the elimination of metallised film which is currently the industry standard approach to achieve the necessary gas barrier performance. Here, we report the synthesis of high aspect ratio 2D non-toxic layered double hydroxide (LDH) nanosheet dispersions using a non-toxic exfoliation method in aqueous amino acid solution. High O 2 and water vapour barrier coating films can be prepared using food safe liquid dispersions through a bar coating process. The oxygen transmission rate (OTR) of 12 μm PET coated film can be reduced from 133.5 cc·m −2 ·day −1 to below the instrument detection limit (<0.005 cc·m −2 ·day −1 ). The water vapour transmission rate (WVTR) of the PET film can be reduced from 8.99 g·m −2 ·day −1 to 0.04 g·m −2 ·day −1 after coating. Most importantly, these coated films are also transparent and mechanically robust, making them suitable for flexible food packing while also offering new recycling opportunities.

a b s t r a c tA new solvothermal post-synthesis treatment for preparing high aspect ratio magnesium aluminium layered double hydroxides (MgAl-LDHs) has been developed. Treating laurate-intercalated MgAl-LDHs in pure ethanol in an autoclave for 48 h at 150 °C was found to produce delaminated MgAl-LDH nanosheets with a thickness of ∼2.6 nm and an aspect ratio of ∼105. It is proposed that the high pressure solvothermal process promotes the insertion of ethanol molecules into the LDH interlayer space, thereby facilitating delamination. This new post-synthesis treatment provides the opportunity for a facile, large scale route to highly delaminated high aspect ratio LDHs, which might be of interest towards novel nanomaterials for energy conversion and storage.

Layered double hydroxides (LDHs) are important materials in the field of catalyst supports, and their surface hydroxyl functionality makes them interesting candidates for supporting well-defined single-site catalysts. Here, we report that the surface hydroxyl concentration can be controlled by thermal treatment of these materials under vacuum, leading to hydroxyl numbers (α) similar to those of dehydroxylated silica, alumina, and magnesium hydroxide. Thermal treatment of [MgAl(OH)](SO)(CO)·0.62(HO)·0.04(acetone) prepared by the aqueous miscible organic solvent treatment method (MgAl-SO-A AMO-LDH) is shown to yield a mixed metal oxide above 300 °C by a combination of thermogravimetric analysis, powder X-ray diffraction (PXRD), BET surface area analysis, and FTIR spectroscopy. PXRD shows the disappearance of the characteristic LDH 00l peaks at 300 °C indicative of decomposition to the layered structure, coupled with a large increase in the BET surface area (95 vs 158 m g from treatment at 275 and 300 °C, respectively). Titration of the surface hydroxyls with Mg(CHPh)(THF) indicates that the hydroxyl number is independent of surface area for a given treatment temperature. Treatment at 450 °C under vacuum produces a mixed metal oxide material with a surface hydroxyl concentration (α) of 2.14 OH nm similar to the hydroxyl number (α) of 1.80 OH nm for a sample of SiO dehydroxylated at 500 °C. These materials appear to be suitable candidates for use as single-site organometallic catalyst supports.

Water adsorbancy of high surface area layered double hydroxides in different relative humidity was investigated. High water inhibition can be achieved via surface modification of LDHs with stearic acid via acid–base reaction.