| Reversible photochromic behavior of ?-Ni(OH)2 with host-guest intercalated structures and non-photochromism of ?-Ni(OH)2 for comparison upon UV irradiation have been reported. The redox reaction between nickel ions on host layers and interlayer guests, that is host-guest electron transfer, contributes to the coloration. In addition, the photosensitive property of ?-Ni(OH)2 is controllable by adjusting the host-guest interactions. Based on the research of crystal structures and pohtochromic mechanism for ?-Ni(OH)2, layered nickel hydroxide salts (LHS-Ni) with different interlayer guests (NO3-, Cl-, SO42- and CO32-) have been synthesized, and the crystal structures and photochemical properties have also been investigated. The interlayer arrangement of LHS-Ni has been studied based on molecular dynamics simulation. LHS-Ni-Ac is non-phtochromic, while layered nickel hydroxide salts with inorganic guests (NO3-, Cl-, SO42- and CO32-) show reversible photochromic behaviors. The pohtochromic mechanism of these systems is different from that of ?-Ni(OH)2. Based on the research of above-mentioned two kinds of layered compounds, series of LDHs with different hosts and interlayer guests have been assembled and they perform different photochemical phenomena. A Ni-Al-NO3 LDH performs reversible photochromism and the mechanism is similar to that of ?-Ni(OH)2. The color of Co-Al-NO3 LDH changes after UV irradiation and only partially restore on heating however. Among the organic guests intercalated LDHs, Ni-Al-LDHs intercalated with p- and m-nitrobenzoate perform coloration after UV irradiation, that could not restore on heating. Such phenomena might belong to photo chemical fields and have relationship with host-guest interactions.
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