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Synthesis, Self-Assembly, Transformation, and Functionalization of Nanoscale Artificial Allophane Spherules for Catalytic Applications

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journal contribution
posted on 19.06.2017, 00:00 authored by Yao Zhou, Hua Chun Zeng
Mesoporous materials with large surface area and chemical inertness are of great importance, and currently prevailing synthetic approaches involve usages of micelles as pore-directing agents to create such mesopores. In this work, allophanes, which are hollow aluminosilicate spherules of 3.5–5.5 nm in size, have been synthesized and assembled simultaneously for the first time in a controlled manner to generate mesoporous spherical allophane assemblages (MSAAs) with diameters of 445 ± 40 nm, specific surface area as high as 1032 m2/g, pore volume 1.104 mL/g at P/P0 = 0.975, and average mesopore size at 3.4 nm. Furthermore, the thus-prepared MSAA could be doped with transition metal ions to create a series of isomorphous derivatives; they could also be converted to aluminum-based hierarchical assemblages of layered double hydroxide easily. Different from the conventional channel-like mesopores, the new mesoporosity attained in MSAA is easily accessible because their mesopores are generated from the interparticle spaces of spherical building units of hollow spherules. Therefore, the mesoporous MSAA provides an excellent platform for construction of integrated nanocatalysts. Highly dispersed noble metal nanoclusters such as Pt, Au, and Pd could be deposited on the surface or in the interior mesopores of the MSAA. Excellent activity and stability of MSAA-based catalysts for Suzuki couplings and electrochemical sensing of H2O2 have been demonstrated using Pd/MSAA and Au/MSAA nanocomposites, respectively.