Design and preparation of new luminescent metal–organic frameworks and different doped isomers: sensing pollution ions and enhancement of gas capture capacity

Abstract

Two new metal–organic frameworks (MOFs), formulated as [Cd₃(L)₂(H₂O)₂]·2H₂O (1) and [Zn₂(L)(OH)(H₂O)]·2DMA (2, DMA = N,N-dimethylacetamide), were first constructed via an unsymmetrical N-heterocyclic 5-((4-carboxypyridin-2-yl)oxy)isophthalic acid (H₃L) ligand. Then, a proportion of the Zn(II) ions of 2 were substituted by fine-tuning the contents of Co(II) ions to obtain two new isomers, Co1-MOF 2 and Co2-MOF 2, the successful doping of which can be proved by PXRD, IR spectra, ICP, XPS, and SEM. The luminescent experiments suggested that complex 1 should be a good detector for detecting Fe³⁺ and Cr₂O₇²⁻ ions. More remarkably, the Co-rich MOF materials have increased gas capture for CO₂ and CH₄ compared to that of the Co-free isomer 2, and the absorption amount of CO₂ and CH₄ may rise with the increasing content of Co(II) ions in the system at higher pressure and lower temperature.