Strong surface acidity, excellent thermal stability, and a large number of micropores extend the applicability of pillared interlayered clays (PILCs) as catalyst supports and shape-selective adsorbents. Microporosity is one of the most significant characteristics of PILCs. Numerous researchers have been looking for ideal pillars for nearly four decades. Inorganic cations with large particle sizes as pillars were reported, including positively charged polymeric hydroxy-cations of Al, Ti, Fe, or their composites such as Al/Ce, Al/Fe, Al/Co, etc. However, to our knowledge, few of these cations are big enough to bring attractive porosity. Though, aluminum pillaring agents are well understood, structures of many other metal polymeric hydroxy-cations need identification and their hydrolysis behaviors require a comprehensive investigation.

Recently, Dr. ZHU Jianxi and the Master candidate WEN Ke from Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, proposed a convenient method to synthesis Keggin-Al₃₀ pillared interlayered montmorillonite (Mt) from Mt and a base-hydrolyzed solution of Al (III) chloride, building on both the previous detection of a new polycation of aluminum  Keggin-Al₃₀ ([Al₃₀O₈(OH)₅₆(H₂O)₂₄]¹⁸⁺) in the hydrolysis solutions of aluminum and the findings that large polycation species can be formed upon additional titration with a hard base, with the Keggin-type structure.  To the best of Dr. Zhu's knowledge, this is the first time that porous pillared interlayered Mt with large Keggin-Al₃₀ pillars has been successfully prepared. This fundamental work may open up entirely new avenues for developing novel PILCs as heterogeneous catalysts and porous adsorbents.

This work was financially supported by National Nature Science Foundation of China (Grant No. 41272060, 41502031, 41572031) and CAS/SAFEA International Partnership Program for Creative Research Teams (Grants No. 20140491534). The study results were published in Microporous and Mesoporous Materials（Zhu JX, Wen K, Zhang P, Wang YB, Ma LY, Xi YF, Zhu RL, Liu HM, He HP. Microporous and Mesoporous Materials. 2017, 242: 256-263.）

Links to the paper：http://www.sciencedirect.com/science/article/pii/S1387181117300392

Fig. 1.Structural representation of (A) Keggin-Al₁₃ and (B) Keggin-Al₃₀  (Image by ZHU Jianxi)