A vesicle-aggregation-assembly approach to highly ordered mesoporous γ-alumina microspheres with shifted double-diamond networks

Yang Liu; Wei Teng; Gang Chen; Zaiwang Zhao; Wei Zhang; Biao Kong; Wael N Hozzein; Areej Abdulkareem Al-Khalaf; Yonghui Deng; Dongyuan Zhao

doi:10.1039/c8sc02967a

A vesicle-aggregation-assembly approach to highly ordered mesoporous γ-alumina microspheres with shifted double-diamond networks

Chem Sci. 2018 Aug 17;9(39):7705-7714. doi: 10.1039/c8sc02967a. eCollection 2018 Oct 21.

Authors

Yang Liu¹, Wei Teng², Gang Chen³, Zaiwang Zhao¹, Wei Zhang¹, Biao Kong¹, Wael N Hozzein^{4

5}, Areej Abdulkareem Al-Khalaf⁶, Yonghui Deng^{1

7}, Dongyuan Zhao¹

Affiliations

¹ Department of Chemistry , Laboratory of Advanced Materials , Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials and iChEM , Fudan University , Shanghai 200433 , P. R. China . Email: dyzhao@fudan.edu.cn.
² State Key Laboratory for Pollution Control , School of Environmental Science and Engineering , Tongji University , Shanghai 200092 , P. R. China.
³ School of Physical Science and Technology , ShanghaiTech University , Shanghai 201210 , P. R. China.
⁴ Bioproducts Research Chair , Zoology Department , College of Science , King Saud University , Riyadh 11451 , Saudi Arabia.
⁵ Botany and Microbiology Department , Faculty of Science , Beni-Suef University , Beni-Suef , Egypt.
⁶ Biology Department , College of Sciences , Princess Nourah bint Abdulrahman University , Riyadh , Saudi Arabia.
⁷ State Key Laboratory of Transducer Technology , Shanghai Institute of Microsystem and Information Technology , Chinese Academy of Sciences , Shanghai 200050 , P. R. China.

Abstract

Alumina materials have widely been used in industrial fields, such as catalysis and adsorption. However, due to the fast sol-gel process and complicated crystalline-phase transformation, the synthesis of alumina materials with both highly ordered mesostructures and crystallized frameworks remains a great challenge. Herein, we report a novel vesicle-aggregation-assembly strategy to prepare highly ordered mesoporous γ-alumina microspheres with unique shifted double-diamond networks for the first time, by using diblock copolymer poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA) as a template and aluminum isopropoxide as a precursor in a tetrahydrofuran (THF)/hydrochloric acid binary solvent. During the gradual evaporation of THF and H₂O, the as-made Al³⁺-based gel/PEO-b-PMMA composites can be obtained through a co-assembly process based on the hydrogen bonding interaction between hydroxyl groups of alumina oligomers and PEO segments of the diblock copolymers. The formed composites exhibit a spherical morphology with a wide size distribution (diameter size 1-12 μm). Furthermore, these composite microspheres possess an inverse bicontinuous cubic mesostructure (double diamond, Pn3[combining macron]m) with Al³⁺-based gel buried in the PEO-b-PMMA matrix in the form of two intertwined but disconnected networks. After a simple calcination at 900 °C in air, the structure of the resultant mesoporous alumina changes to a relatively low symmetry (shifted double diamond, Fd3[combining macron]m), ascribed to the shifting of the two alumina networks due to loss of the templates. Meanwhile, the unit cell size of the alumina mesostructure decreases from ∼131 to ∼95 nm. The obtained ordered mesoporous alumina products retain the spherical morphology and possess ultra-large mesopores (∼72.8 nm), columnar frameworks composed of γ-alumina nanocrystalline particles (crystal size of ∼15 nm) and high thermal stability (up to 900 °C). As a support of Au nanoparticles, the formed Au/mesoporous γ-alumina composite catalysts have been used in the catalytic reduction of 4-nitrophenol with a high kinetic constant k of 0.0888 min^-1, implying promising potential as a catalyst support.