A multifunctional metal–organic framework with a μ3-OH− site for gas and vapor sorption and selective detection of nitrofurantoin

Abstract

A porous 3D multifunctional Zn-MOF (1), namely {[Zn_2.5(DDPP)(OH)(H₂O)]·H₂O·1.5DMF}_n (H₄DDPP = 3,5-di(2′,5′-dicarboxylphenyl)pyridine, DMF = N,N-dimethylformamide), was solvothermally synthesized by the reaction of a H₄DDPP ligand and zinc salts. 1 exhibits a high adsorption performance for N₂ (246.2 cm³ g⁻¹ at 77 K) and CO₂ (116.1 cm³ g⁻¹ at 273 K) as well as excellent selective separation for CO₂/CH₄ (V : V = 0.5 : 05) and CO₂/CH₄ (V : V = 0.05 : 0.95) with selectivity coefficients of 79.3 and 25.4 at 298 K and 1 bar, respectively. Meanwhile, 1 shows a great performance for H₂O vapor sorption and the uptake amount of H₂O vapor is 281.9 cm³ g⁻¹ (at 298 K and P/P₀ = 0.99), which is comparable to that reported in the literature. Furthermore, 1 has an excellent separation ability for H₂O vapor in H₂O/CH₃OH mixed vapor and the selectivity of 1 for H₂O/CH₃OH (V : V = 0.1 : 0.9) and H₂O/CH₃OH (V : V = 0.05 : 0.95) is 254.6 and 94.9 at 298 K and 1 bar, respectively. More importantly, the Grand Canonical Monte Carlo (GCMC) simulation shows that the reason for the good adsorption capacity of 1 for CO₂ and H₂O vapor is attributed to the pore structure of 1 and the interaction between the coordinated H₂O molecules and μ₃-OH⁻ in 1 and CO₂ or H₂O molecule. In addition, 1 shows sensitive sensing ability for nitrofurantoin (NFT) and the detection limit (DL) was 5.3 × 10⁻⁸ M. Moreover, the fluorescence sensing mechanism of 1 for NFT can mainly be attributed to the competitive absorption between the absorption spectrum of NFT and the emission spectrum of 1, the weak interactions between μ₃-OH⁻ in 1 and NFT and photoinduced electron transfer from 1 to NFT.