Structure co-ordination of solitary amino acids as ligands in metal-organic frameworks (MOFs): A comprehensive review

Amino acids are the chiral ligands which are having more affinity towards metal ion centers of higher valence. The chirality of the amino acid restricts its ability to form three-dimensional networks. But the amino acids are easily forming one- (rod-like or chain-like) and two-dimensional (plane-like) structures when coordinated with metal ion centers and further interconnected with other primary ligands. Other than the amine and carboxyl groups, the side chain functional groups are specifically contributed by coordinating with metal ion centers to construct the Metal-Organic Frameworks (MOFs). Solitary amino acids act as ligands in MOFs synthesis with metal ion centers is selectively based on the number of coordination sites. The amino acids ligands offer non-toxicity and environmental-friendly nature to the MOFs. Due to the constrain of chirality in forming three-dimensional MOF networks, the amino acids are widely used as modifying and functionalizing agents along with other primary ligands. The present review offers an overview on the role of solitary amino acid ligands in MOF synthesis along with their coordination modes and consolidated applications.