Micrometer-sized dihydrogenphosphate-intercalated layered double hydroxides: synthesis, selective infrared absorption properties, and applications as agricultural filmsElectronic supplementary information (ESI) available. See DOI: 10.1039/c7dt03483k

High-performance heat-retention agents for multifunctional green agricultural films are today largely suitable to increase the production yield as well as to save energy. Here, an adapted ammonia releasing hydrothermal method was used to produce a series of micrometer-sized carbonate-layered double hydroxide (CO 3 -LDH) precursors of sizes ranging from 1.32 μm to 8.64 μm by simply adjusting the feeding Mg 2+ concentration from 0.80 mol L −1 to 0.20 mol L −1 . From these pristine LDH materials, μm-sized dihydrogenphosphate-intercalated LDHs (H 2 PO 4 -LDHs) were prepared by an anion-exchange method. The structure, the platelet size, and the associated selective IR absorption properties of the H 2 PO 4 -LDH and the derivative H 2 PO 4 -LDH/EVA composite as well as the related visible transmittance and the photostability of the H 2 PO 4 -LDH/EVA film were investigated. The results show that the selective IR absorption in the wavelength range of 7-14 μm enabling the heat retention of the H 2 PO 4 -LDHs and H 2 PO 4 -LDH/EVA composites depends on the corresponding number-averaged particle size of H 2 PO 4 -LDH in the range of 2.01 μm to 8.80 μm. Compared with EVA, the H 2 PO 4 -LDH/EVA composites demonstrate a significant improvement of selective IR absorption, while maintaining acceptable visible transmittance, and similar photostability. An optimized particle size of H 2 PO 4 -LDH of ca. 5.85 μm leads to 60% selective IR absorption and 64% selective IR absorption when dispersed in EVA, while the polymer free of filler exhibits less than 50% absorption in the 7-14 μm IR domain. Controllable synthesis and selective IR absorption properties of micrometer-sized H 2 PO 4 -LDHs were investigated in details as well as the structure-performance relationship.