In this work, the function of 4-nitroimidazole (4-NIm) in the formation of Cr-MIL-101 was confirmed. It was found that 4-NIm is an effective additive in the formation of Cr-MIL-101 synthesized at lower temperature. The investigation of crystallization time showed that 4-NIm can prevent Cr-MIL-101 phase converting into Cr-MIL-53 phase. The effect of concentration of 4-NIm on the morphology and the yield of Cr-MIL-101 may therefore be explained by increasing the nucleation rate. The investigation of crystallization temperature revealed that 4-NIm changes the synthesis temperature range of Cr-MIL-101 into 423–463 K. The assistant function of 4-NIm was played through interaction with H + and NO 3 − in the synthesis system, which may lead to enhancement of the deprotonation of H 2 BDC.
The pollution of aromatic organophosphorus flame retardants (aromatic OPFRs) in aquatic environments has drawn great attention over the last few years. Two MIL-101-based metal–organic frameworks (Cr-MIL-101 and Fe-MIL-101-NH2) which possess ordered mesoporous cavities (2.9 and 3.4 nm) and aromatic structures were chosen and prepared to selectively adsorb a typical aromatic OPFR [triphenyl phosphate (TPhP)] from aqueous solution. Pore distribution analysis showed that Cr-MIL-101 and Fe-MIL-101-NH2 had both a mesoporous structure (2–3.5 nm) and microporous structure (1–2 nm), conducive to diffusion and adsorption of TPhP molecules. Compared with Fe-MIL-101-NH2 as well as commercial activated carbon, Cr-MIL-101 showed rapid and efficient adsorption for TPhP, and its initial sorption velocity (v0) calculated from the pseudo-second-order model was up to 568.18 μmol g−1 h−1. The adsorption equilibrium of TPhP on the Cr-MIL-101 was almost achieved within 12 h, while the equilibrium time of other adsorbents required more than 48 h. The study of selective adsorption found that Cr-MIL-101 had a higher sorption amount for aromatic OPFRs than alkyl-OPFRs and other aromatic compounds with different chemical structures. Cr-MIL-101 was able to keep a steady selective adsorption for TPhP in the presence of co-existing aromatic compounds. Based on the analysis of Kow, molecular structure and further density functional theory calculations, hydrophobic interactions may play a dominant role in the selective adsorption process of TPhP, and π–π interactions may be also involved. Cr-MIL-101 exhibits reusability and promising potential to rapidly and selectively remove aromatic OPFR in environmental remediation.
Mengyue Gao,Qiao Chen,ZhiHao Li,YiFang Zhan,LiHua Wang,Ting He,Qi Yao,Fengmei Jin,Jiming Hu
A SPE-SERS method was developed for the detection of several antibiotic residues in dairy products. Gold nanoparticles (Au NPs) encapsulated with an ultrathin Cr-MIL-101 shell (Au@Cr-MIL-101 NPs) have been synthesized, and the thickness of Cr-MIL-101 shell can be precisely controlled to 3 nm. As a superior solid phase extraction (SPE) adsorbent, Cr-MIL-101 acts as a shell layer to effectively enrich antibiotics within the localized surface plasmon resonance (LSPR) field of Au NPs, which enhances the SERS signal and eliminates background interference. The method can achieve highly sensitive and high-throughput detection for tetracycline hydrochloride, sulfapyridine and benzylpenicillin sodium in dairy products, and the detection limits (LOD) are as low as 2.237, 2.644 and 4.662 ppb respectively. The recoveries of antibiotic residues in spiked dairy products ranged from 72.31 % to 146.7 % with matrix effects (ME) of −15.13 % to 28.68 %. Thus, this method holds significant promise for rapid detection of antibiotics in milk.
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