Precise regulating synergistic effect in metal–organic framework for stepwise-controlled adsorption

Abstract

Porous materials bearing stepwise-controlled pore-shape change that are capable of executing sophisticated tasks are of considerable interest due to their fascinating features. In this work, we present a (3,4,6)-connected metal–organic framework built of 1D hinge-like zig–zag chain and tritopic ligand, formulated as (H₃O)₂[Zn₃(dmtrz)₂(tipa)₂]·4H₂O (MAC-20, Hdmtrz = 3,5-dimethyl-1H-1,2,4-triazole, H₃tipa = 5-(2H-tetrazol-5-yl)isophthalic acid). By regulating the hinge angle and hydrogen bond interaction of 1D chain and tritopic ligand precisely, we realize a unique two-step pore-shape change in MAC-20 structure, which reveals that 1D chain and tritopic ligands have a synergistic effect on the structural transformation. Furthermore, the MAC-20 structure executes the sequential adsorption of indigo blue (ID) and sudan-I (SD-I) stepwise-controlled by trimethylamine and N,N-dimethylformamide, which offers the potential to exploit the flexible MOFs for smart multi-step stimuli-responsive applications.