Organic-Additive-Assisted Synthesis of Hierarchically Meso-/Macroporous Titanium Phosphonates

Organic-inorganic hybrid materials of meso-/macroporous titanium triphosphonate materials were synthesized by using amino tri(methylene phosphonic acid) as the coupling molecule. The preparation was accomplished by a hydrothermal process in the presence or absence of small amounts of the diblock copolymer EO30PO34 and (3-cyclodextrin as the organic additives. The organic-additive-assisted preparation efficiently aided the enlargement of the surface areas and pore volumes of the resultant porous titanium triphosphonates and helped improve the wormhole-like mesoporosity. In addition to the large macrochannels, with a size of 500-1000 nm, observed in all the titanium phosphonates synthesized with or without organic additives, a secondary small-scaled, spherical macroporous structure with a diameter of 50-100 nm was obtained by the addition of cyclodextrin. These macroporous structures are proposed to be templated by the aggregation of cyclodextrin. The structural characterization confirms the integrity of organic groups inside the framework. Large adsorption capacities for heavy metal ions and CO2 are demonstrated in these hybrid materials, which makes them promising adsorbents for practical applications.