The continuous demand for acidic solids for use in the fields of catalysis and sorption has greatly encouraged the search for new materials with a porosity and intrinsic reactivity that can be tailored. [1] The synthesis of the family of M41S solids has shown that surfactant species favor, by a mechanism of cooperative nucleation, the formation of organo-inorganic nanocomposite biphase arrays, the structures of which mimic those of liquid crystals. [2,3] This synthetic approach is demonstrating its importance by its versatility, and a great variety of mesoporous solids have been prepared since the landmark articles of Beck et al. We report here the sol-gel synthesis of zirconium phosphate in the presence of a structure-directing cationic surfactant, leading to mesoporous solids with a BET (Brunauer±Em-mett±Teller) surface area of ca. 250±320 m 2 g ±1 and a high and modulable surface acidity following removal of the surfactant by acid±ethanol extraction or by calcination at 540 C.Zirconium phosphate is the most studied member of the well-known family of layered solid acids. [4] ªPillaredº derivatives can be prepared by intercalation of inorganic or organometallic species followed by a grafting reaction designed to eliminate organic matter, dehydroxylate, and anchor the pillaring metal oxide nanoparticle formed to the layer. These multifunctional zeolite-like compounds are meso-and microporous, and have potential applications as catalysts and catalyst supports. [5] Although templated syntheses of open-framework phosphates has been developed as a route to ultra-large pore solids, [6] until very recently, surfactant-assisted syntheses of metal phosphates led only to layered phases, [7] and the synthesis of mesoporous phosphate-based solids with pore dimensions larger than those of the aluminum phosphates remained a challenge. Last year, however, Zhao et al. reported the preparation of a thermally stable mesoporous hexagonal aluminophosphate and silicoaluminophosphate with BET surface areas of 772 and 928 m 2 g ±1 , respectively. [8] Some months earlier, Ciesla et al. had recourse to phosphoric acid treatment of a surfactant-containing zirconium oxosulfate gel, which, by neutralizing the remaining ZrOH groups, helped to avoid the structural collapse of the zirconium oxide on removal of the surfactant. This led to high surface area zirconium oxophosphate. [9] In a different approach, we have used phosphoric acid directly at the stage of the formation of the inorganic matrix, and now report the templated synthesis and characterization of a new mesoporous zirconium phosphate with uniform pore dimensions and acidic properties.The synthesis of this new templated zirconium phosphate (t-ZrP) was carried out by mixing an aqueous solution of cetyltrimethylammonium (CTMA) bromide (25 wt.-%, Aldrich) with orthophosphoric acid (85 wt.-%, BDH Analar) (P/CTMA molar ratio = 1). The CTMA solution was then aged for at least 30 min before adding zirconium n-propoxide (Zr(OC 3 H 7 ) 4 , 70 wt.-% solution in 1-propanol, Aldrich), in...