A density functional theory study on the structure formation of Al(III) carboxylate complexes in aqueous aluminum sols

• Published in: International journal of quantum chemistry Vol. 121; no. 2
• Main Authors: Li, Chunlan, Liu, Wensheng, Wang, Juan, Yao, Shuwei, Ma, Yunzhu
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 15.01.2021; Wiley Subscription Services, Inc
• Subjects: Acetic acid; Al powder; Aluminum; aluminum sols; Aqueous solutions; Chemistry; Density functional theory; Dimers; formic and acetic acid; Hydrates; Monomers; Physical chemistry; Precursors; Quantum physics; Sol-gel processes; Sols; structure; Water chemistry
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/qua.26430

In‐depth studies of the structure of precursor sols is very important for understanding the subsequent sol to gel transition. Here, density functional theory was applied to study the reaction of Al powder with formic and acetic acid in aqueous solution to find the structure of Al(III) complex in precursor sols. The Al3+ ion obtained by dissolving Al powder in aqueous solution of formic and acetic acid would preferentially coordinate with water molecules to form aluminum hydrates. As the reaction energy barrier of aluminum hydrates with CH3COO− and HCOO− was comparable, both aluminum formoacetate and other aluminum carboxylate monomers could be obtained. Most Al(III) complexes formed by other carboxylate monomers were similar to that prepared from aluminum formoacetate. However, some Al(III) monomers and Al(III) dimer with different structural characteristics might be detrimental to the formation of linear polymers. The formation of other aluminum carboxylate monomers had great influence on the structure of precursor sols. The reaction process of Al powder with HCOOH and CH3COOH in aqueous solution was studied by DFT calculations. The coordination of Al3+ with water molecules is more thermodynamically favorable. Due to the similar properties of HCOO− and CH3COO−, aluminum formoacetate and other monomers can be obtained simultaneously. These other monomers will lead to the formation of some aluminum carboxylate oligomers with different structural characteristics, which will have great influence on the spinnability of precursor sols.