Electron Transfer Reduction by Hydrogen Creates Porosity in Tantalate Crystals and Produce Multifunctionality

Contrary to partially substituted systems, WO 3 molecular sieves that exclusively comprise a d 0 transition metal ion and do not possess template ions in the cavity are a new class of materials for photocatalysis owing to their framework structure. Because WO 3 thermodynamically lacks proton-reduction capability, exploring diverse synthetic approaches of other materials is desirable for facilitating utilization as H 2 evolution and water splitting systems. Herein, we report an efficient approach for the protonation of Ag 2 Ta 4 O 11 to afford H 2 Ta 4 O 11 for application as a H 2 molecular sieve. Hydrogen reduction of Ag 2 Ta 4 O 11 at 300 °C and post-treatment using HNO 3 afforded H 2 Ta 4 O 11 . Characterizations of H 2 Ta 4 O 11, coupled with density functional theory (DFT) calculations, reveal that the intrinsic structure of Ag 2 Ta 4 O 11 is maintained. Moreover, H + is generated from H 2 oxidation and forms OH, and the orientation of OH is parallel to that of the ab plane. Desorption and adsorption of H 2 within H 2 Ta 4 O 11 were achieved by heating H 2 Ta 4 O 11 to above 90 °C. This is attributed to positive thermal expansion, as confirmed by high-temperature X-ray diffraction. H 2 Ta 4 O 11 is an active heterogeneous photocatalyst for the half-reactions of water splitting. Moreover, deuteration experiments of H 2 Ta 4 O 11 in D 2 O suggest its capability as a H 2 –D 2 conversion catalyst. Furthermore, H 2 Ta 4 O 11 functions as an active synthetic precursor for new tantalate materials, the direct synthesis of which is challenging.