A responsive supramolecular-organic framework: Functionalization with organic laser dye and lanthanide ions for sensing of nitrobenzene
Graphical abstract
SOF-1 exhibited highly efficient adsorption of organic laser dye. Moreover, Eu3+@SOF-1 for chemical sensing can be easily prepared by postsynthetic method.
Introduction
Crystalline porous frameworks have attracted significant attentions due to their novel structures and potential applications in the fields of sensor, catalysis, drug delivery, gas sorption and separation [[1], [2], [3]]. Various crystalline porous frameworks with high surface area, tunable skeleton, and physical and chemical stability have been reported, such as covalent organic frameworks (COFs) [1], metal-organic frameworks (MOFs) [2], supramolecular-organic frameworks (SOFs) [3]. Of them, MOFs and COFs have been most actively investigated. In MOFs and COFs, the crystalline porous frameworks are robustly stabilized by strong bonds such as coordination or covalent bonds to maintain their porosity. Compared with MOFs and COFs, highly crystalline SOFs materials that rely on weak interactions to stabilize their framework, are often too labile for their wide adoption in environment settings. On the other hand, SOFs using weak noncovalent interactions have the potential to gain structural flexibility, which leads to unique properties such as dynamic and guest responsive adsorption behaviors. The structural reponse of these SOFs materials to external stimuli is expected to facilitate the development of porous materials for molecular sensors.
Lanthanide-functionalized MOFs have attracted intense interest for their functional properties and potential application in light-emitting devices, chemical sensing, biological imaging and biomedicine, etc. [4] Recently, some groups have made excellent progress on using lanthanide-functionalized MOF hybrid materials to create multiple luminescent centers for chemical sensing such as detect small molecules, gases, temperatures, pH values, metal cations and anions [5]. To the best of our knowledge, lanthanide-functionalized porous materials based on SOFs for chemical sensing have not been reported. Inspired by these pioneering works, we reasoned that by using SOFs instead of MOFs, new lanthanide-functionalized porous materials based on SOFs could be expected.
Organic solid-state dye lasers can be constructed by dispersing organic laser dyes in solid-state hosts, such as zeolites, clays, sol-gel glasses, MOFs and SOFs microcrystal [[6], [7], [8], [9], [10], [11]]. But until now, very few solid-state hosts for organic laser dyes based on SOFs microcrystal are known. Very recently, Ward et al. reported the sequestration of organic laser dyes within supramolecular polyhedral compartments of a crystalline zeolite-like hydrogen-bonded framework [11]. It is still an attractive but challenging task for exploiting new solid-state hosts for organic laser dyes based on SOFs microcrystal. Regarding the construction of SOFs structures, we focus on the design and synthesis of porous structures based on calixarenes. Calixarenes as building blocks have been widely used in the field of supramolecular chemistry due to their novel structures and potential applications in material science [12]. The usability of the calixarenes for constructing porous structures has been demonstrated by many reports [13,14]. In this paper, we reported a SOF-1 based on p-sulfonatocalix[4]arene, which exhibited highly efficient adsorption of organic laser dye (4-[p-(dimethylamino)styryl]-1-methylpyridinium, DSM). In addition, we prepared a responsive luminescent Eu3+@ SOF-1 by postsynthetic incorporation of Eu3+ cations into the SOF-1 framework, which can serve as a platform for the recognitions of nitrobenzene (Fig. 1 and Fig. S1).
Section snippets
Materials and instrumentation
All reagents were commercial products of high purity and were not further purified except (NH4)5·[p-sulfonatocalix[4]arene] which was prepared via the ammonia water reaction with p-sulfonatocalix[4]arene. The powder X-ray diffraction (XRD) of the compounds were examined on a Rigaku-Dmax 2500 diffractometer using Mo Kα radiation (λ = 0.15405 nm). Fourier transform infrared (FTIR) spectra were measured within the 4000-400 cm-1 wavenumber range using a Perkin-Elmer model 580B IR
Crystal structure description of SOF-1
The SOF-1 was synthesized through the reaction of ZnCl2·6H2O, (NH4)5·[p-sulfonatocalix[4]arene] and bpdo in a 3:2:9 M ratio (pH=6) in the presence of water. In SOF-1, we choosed (NH4)5·[p-sulfonatocalix[4]arene] based on the following considerations: 1) we considered that NH4+ is easiler to exchange with lanthanide ions or DSM for post-functionalization; 2) A survey of the Cambridge Structural Database shows that bpdo can form various complexes with metal ions under different conditions,
Conclusions
In summary, SOF-1 has been successfully synthesized by employing [Zn(bpdo)2·2H2O]2+ and p-sulfonatocalix[4]arenas nanocapsules, which are sustained exclusively by weak interactions. By counter-ion exchange, Eu3+@SOF-1, DSM@SOF-1 and MB@SOF-1 can be easily prepared by postsynthetic method. The Eu3+@SOF-1 was developed as efficient luminescent probe for the sensing of nitrobenzene. Unlike other nanoporus materials, SOF-1 is easily regenerated in hot water. The result affords us numerous
CRediT authorship contribution statement
Danyong Jiang: Writing - original draft, Methodology. Huaifang Fang: Resources. Gang Li: Visualization. Guoli Zheng: Supervision, Conceptualization, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors are grateful to the financial aid from the National Natural Science Foundation of China (Grant No. 21201051).
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