Defective Hierarchical Pore Engineering of a Zn-Ni MOF by Labile Coordination Bonding Modulation

The construction and modulation of hierarchical pore structure in metal-organic frameworks (MOFs) has become a hot topic owing to the advantages of hierarchical pore MOFs (HP-MOFs) in matter storage and mass transfer related applications. Herein, we report the engineering of crystalline defect in a bimetallic MOF for the construction and tuning of HP-MOF. A microporous MOF system showing metal-center-dependent water stability, namely, {[M3F(bdc)(3) tpt] (solvents)}(n) (M = Zn2+ and Ni2+, H(2)bdc = 1,4-benzenedicarboxylic acid, tpt = 2,4,6-tris(4-pyridyl)triazine), was utilized as a platform for the construction of HP-MOF. By tuning the Zn2+/Ni2+ ratio in the reactant, a bimetallic MOF with a highly tunable Zn2+/Ni2+ ratio could be obtained. The relatively labile Zn2+-based coordination bonding in the bimetallic MOF could be readily and targeted broken through water treatment for the engineering of crystalline defects-based hierarchical pore structure. The resultant HP-MOF reveals a dramatically increased pore volume with the presence of mesopore and macropore. In addition, the anionic framework of HP-MOF could be utilized for the selective adsorption of a cationic dye methylene blue, and a relatively high capacity (250 mg.g(-1), five times compared with the pristine microporous MOF) could be achieved.

Automated summary

The study focuses on engineering a bimetallic MOF with a tunable Zn2+/Ni2+ ratio for the construction and tuning of a hierarchical pore MOF. The resulting HP-MOF shows increased pore volume with mesopore and macropore, and also exhibits selective adsorption capacity for cationic dye methylene blue, achieving a relatively high capacity compared to the pristine microporous MOF.