Insights into the Mechanochemical Synthesis of MOF-74

Abstract

Mechanochemical synthesis has recently emerged as a scalable “green” approach for the preparation of MOFs, but current understanding of the underlying reaction mechanisms is limited. In this work, an investigation of the reaction pathway of the mechanochemical synthesis of MOF-74 from ZnO and 2,5-dihydroxyterephthalic acid (H 4 HDTA), using DMF as a liquid additive, is presented. The complex reaction pathway involves the formation of four short-lived intermediate phases, prior to the crystallization of MOF-74. The crystal structures of three of these intermediates have been determined using a combination of single-crystal and powder X-ray diffraction methods and are described here. The initial stages of the reaction are very fast, with a DMF solvate of H 4 HDTA forming after only 2 min of milling. This is followed by crystallization, after only 4 min of milling, of a triclinic one-dimensional coordination polymer, Zn(H 2 DHTA)(DMF) 2 (H 2 O) 2 , which converts into a monoclinic polymorph on additional milling. Highly crystalline MOF-74 appears after prolonged milling, for at least 70 min.

Metal organic framework for hydrogen storage

“…MOF-74 is synthesized through the mechanochemical method, using ZnO and 2,5-dihydroxyterephthalic acid (H4HDTA) with DMF as a solution. They have a high-density open metal sieve and high porosity for hydrogen capture [8].…”

The unique opportunities of mechanosynthesis in green and scalable fabrication of metal–organic frameworks

“…Vaqueiro group demonstrated the key role of the solvent in the reaction pathway taken place under mechanosynthesis conditions. 205 Ball milling of a mixture of ZnO and H 4 dhta in the presence of DMF revealed a complex reaction pathway in which four different intermediate phases were formed prior to the formation of Zn-MOF-74 after 70 min milling. It was concluded that DMF molecules with more steric hindrance than water molecules not only occupy the pores of the final MOF-74, but also incorporate into the structures of the intermediate phases.…”

“…stepwise studies revealed an unexpected reaction mechanism in which a close-packed intermediate transformed into an open porous structure (Fig.16). Vaqueiro group demonstrated the key role of the solvent in the reaction pathway taken place under mechanosynthesis conditions 205. Ball milling of a mixture of ZnO and H 4 dhta in the presence of DMF revealed a complex reaction pathway in which four different intermediate phases were formed prior to the formation of Zn-MOF-74 aer 70 min milling.…”

Recent Advances in MOF-Based Adsorbents for Dye Removal from the Aquatic Environment

“…The most important advantages of MOF over other adsorbents are structural diversity [39], the possibility of determining the size of the pores, as well as determining the properties and performance by selecting various metal nodes and organic ligands in the synthesis stage. Various methods such as solvothermal [40], hydrothermal [41], mechanochemical [42], sonochemical [43], spray drying [44], sol-gel [45], and flow chemistry [46] have been used in MOFs synthesis. Another advantage of MOFs over other adsorbents is the low energy required for the regeneration process [47], large surface area [48], as well as high thermal and mechanical stability [49].…”