Catalytic and sorption applications of porous nickel phosphate materials

Porous nickel phosphates, denoted as VSB-1 (Versailles-Santa Barbara-1) and VSB-5 (Versailles-Santa Barbara-5), are crystalline metal phosphate microporous molecular sieves with zeolitic properties. These nickel phosphates could be used as functional catalysts and adsorbents due to interesting properties to readily accommodate many transition metal elements in their frameworks besides zeolitic properties as well as the presence of framework nickel (II) ions. In this account, we provide an overview of selected results regarding their catalytic and sorption applications which have been published in the literature. VSB-1 and VSB-5 are similar to zeolites in many aspects and may be suitable for use as adsorbents for the separation of molecular species and as catalysts or catalyst supports. Particularly, these materials possess unique catalytic properties suitable for several reactions that do not require strong acidity. Isomorphous substitution of Ni2+ with divalent or trivalent transition metals in a nickel phosphate structure can generate new redox centers and Bronsted-Lewis acid centers, providing interesting catalytic properties. Based on an understanding of the formation mechanism of nickel phosphate, VSB-5 was used in electrochemical applications and showed unusual surface chemistry of coordinatively unsaturated Ni2+ sites accessible in its pores.