Do the acid/base modifiers in solvothermal synthetic conditions influence the formation of Zr-Tyr MOFs to be amorphous?

Abstract

Synthesis of MOFs with properties like pore size, rigidity, reusability, chemical, and mechanical stability is the most modern research in coordination chemistry. Controlling the choice of organic ligand, and metal centre which acts as bridging point, are the two prominent aspects during the synthesis of MOFs. Herein we report, the synthesis of MOFs using a transition metal zirconium ion and amino acid L-tyrosine as a metal centre and organic ligand, respectively. The Zr-Tyr MOFs are synthesized with different conditions (specifically, extreme pH conditions) such as, with Conc. HCl, neutral, and with Conc. NaOH, because of the crucial influence of pH in the structural properties of the MOFs. The resultant properties such as crystallinity, surface area, pore diameter and volume of synthesized Zr-Tyr MOFs using efficient, zwitterionic, bifunctional, and eco-friendly organic ligand L-tyrosine are discussed. Though the aim is to synthesize crystalline MOF, surprisingly, the resulted MOFs depicted amorphous to partially crystalline nature at the basic condition. They have potent applications due to their thermal and chemical stability. Among the three resultant MOFs, Zr-Tyr MOF synthesized with Conc. NaOH possesses increased specific surface area, average pore diameter, and total pore volume of 294 m2/g, 8.15 nm, and 0.6 cm3/g respectively. This best resulted Zr-Tyr MOF synthesized with Conc. NaOH exhibits improved crystallinity and multilayer pore formation.