Copyright © 2014 American Scientific Publishers All rights reserved Printed in the United States of America Review Journal of Nanoscience and Nanotechnology Vol. 14, 1931–1946, 2014 www.aspbs.com/jnn Nanostructured Mg–Al Hydrotalcite as Catalyst for Fine Chemical Synthesis Sulaiman N. Basahel 1 2 , Shaeel A. Al-Thabaiti 1 2 , Katabathini Narasimharao 1 2 , Nesreen S. Ahmed 1 , and Mohamed Mokhtar 1 2 ∗ 1 Faculty of Science, Chemistry Department, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia 2 Surface Chemistry and Catalytic Studies Group, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia This paper reviews the recent research of nanostructured Mg–Al hydrotalcite (Mg–Al HT) and its application as an efficient solid base catalyst for the synthesis of fine chemicals. Mg–Al HT has many beneficial features, such as low cost, selectivity, catalytic properties, and wide range of prepa- ration and modification methods. They hold promise for providing sought-after, environmentally friendly technologies for the 21st century. Replacement of currently used homogeneous alkaline bases for the synthesis of fine chemicals by a solid catalyst can result in catalyst re-use and waste stream reduction. We introduce briefly the structure, properties and characterization of the nanos- tructured Mg–Al HT. The efficacy and benign applications of Mg–Al HT as an alternative solid base to homogenous catalysts in the synthesis of fine chemicals are then reviewed. The challenges for the future applications of Mg–Al HT in the synthesis of fine chemicals in terms of green protocol processes are discussed. Keywords: Nanostructured, Hydrotalcite, Anionic Clays, Layered Materials, Processing and Characterization, Materials Properties, Fine Chemicals, Green Protocol, Microwave Irradiation. CONTENTS 1. Introduction ........................................ 1931 1.1. History ........................................ 1933 2. Structure of Hydrotalcites ............................. 1933 2.1. Brucite Layers .................................. 1933 2.2. Cations in Brucite Layers ......................... 1933 2.3. Hydrotalcite Interlayer ............................ 1934 3. Structural Properties of Hydrotalcites .................... 1934 4. Synthesis of Hydrotalcites ............................. 1935 4.1. Coprecipitation Method ........................... 1935 4.2. Urea Hydrolysis ................................. 1935 4.3. Hydrothermal Treatment .......................... 1936 4.4. Combustion Synthesis ............................ 1936 4.5. Sol–Gel Method ................................. 1936 4.6. Microwave Irradiation ............................ 1937 5. Characterization of Hydrotalcites Using Physicochemical Methods ............................. 1937 6. Mg–AlHT as Solid Base Catalyst in Fine Chemical Synthesis . 1940 6.1. Condensation Reactions ........................... 1940 6.2. Oxidation Reactions .............................. 1942 6.3. Transestrification Processes ........................ 1942 7. Environmentally Benign Methodologies Using Mg–AlHT Catalyst ............................. 1943 ∗ Author to whom correspondence should be addressed. 7.1. Ultrasonic Method ............................... 1943 7.2. Microwave Assisted Reactions ...................... 1943 8. Concluding Remarks ................................. 1943 Acknowledgments ................................... 1944 References and Notes ................................ 1944 1. INTRODUCTION Hydrotalcites (HTs) are a class of ionic lamellar com- pounds made up of positively charged brucite-like layers with an interlayer portion containing charge compensat- ing anions and solvation molecules. The metal cations occupy the centers of edge sharing octahedra, whose ver- texes contain hydroxide ions that connect to form infinite 2D sheets. The most widely studied HTs contain both diva- lent and trivalent metal cations, a generic formula for these HTs can be represented as: [M II 1−x M III x (OH) 2 ][A n− ] x/n · yH 2 O, where M II may be common; Mg II , Zn II , or Ni II and M III may be common; Al III , Ga III , Fe III , or Mn III . A n− is a non-framework charge compensating inorganic or organic anions, e.g., CO 2− 3 , Cl − , SO 2− 4 , RCO 2− , and x is normally between 0.2–0.4. 1–4 HTs may also con- tain M I and M IV cations but these are limited to specific J. Nanosci. Nanotechnol. 2014, Vol. 14, No. 2 1533-4880/2014/14/1931/016 doi:10.1166/jnn.2014.9193 1931