Design and Construction of the Uranyl Coordination Polymer with Multifunction Stimulus Response: Fluorescent Sensors for Halide Ions and Photochromism.

It can provide ideas for the use of uranium elements in the treatment of spent fuel from nuclear wastewater to explore the application potential of uranium element. Thus, it is necessary to research the structure and properties of a novel uranyl coordination polymer (CP) for uranium recovery and reuse. Herein, we designed and prepared a new uranyl CP U-CMNDI based on UO22+ and H2CMNDI (H2CMNDI = N, N'-bis(carboxymethyl)-1,4,5,8-naphthalenediimide). Structural analysis shows that two uranyl ions are connected by two parallel deprotonated CMNDI ligands to form a discrete uranyl dimer structure. U-CMNDI can act as a potential stimulus-responsive halide ion sensor by a fluorescence "turn on" response in water. The limit of detection for fluoride (F-), bromide (Br-), iodide (I-), and chloride (Cl-) is 5.00, 5.32, 5.49, and 5.73 µM, respectively. The fluorescence "turn on" behavior is based on the photoinduced electron transfer (PET) mechanism between halide ions and electron-deficient NDI cores. In addition, U-CMNDI demonstrates a color response to ultraviolet light, exhibiting reversible photochromic behavior with a notable color change. The color change mechanism can contribute to the PET process and the radical process.

A UOF based on a cyclotriphosphazene skeleton: fluorescence sensing of different substituted aldehydes and NACs.

A novel uranyl organic framework (U-hdpcp) based on flexible cyclic triphosphazene polycarboxylate ligands was prepared, which possesses the ability to sense aromatic aldehyde solutions (benzaldehyde, salicylaldehyde and 2-bromobenzaldehyde) and nitro compounds (2,4,6-trinitrophenol, 2,4-dinitrophenol and o-nitrophenol). A fluorescent thin film based on U-hdpcp@PVA with the ability to sense aldehyde vapors was prepared via a spin coating method. The work expands the library of UOF materials based on large-sized carboxylic acid ligands and demonstrates promising applications in the field of fluorescent sensors.

Cage Bismuth Metal-Organic Framework Materials Based on a Flexible Triazine-Polycarboxylic Acid: Subgram Synthesis, Application for Sensing, and White Light Tuning.

Bismuth-based metal-organic frameworks (MOFs) have always attracted the attention of many researchers. Here, we first report a crystalline Bi-MOF (Bi-TDPAT) based on a flexible triazine-polycarboxylic linker 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine (H6TDPAT) and bismuth nitrate; its crystallite quality is adequately good and the diffraction data can be collected directly by single crystal X-ray diffraction rather than 3D electron diffraction. The structure of Bi-TDPAT belongs to a novel topology type btt. Notably, the synthesis scale of Bi-TDPAT can be expanded, and sub-gram synthesis can be realized. At the same time, we synthesized a microcrystalline material Bi-TATAB utilizing 2,4,6-tris(4-carboxylphenylamino)-1,3,5-triazine (H3TATAB). The structures of the two materials were characterized by several microanalysis tools. Considering that Bi-TDPAT is a blue light-emitting material with a broad emission peak, we prepared a white light emitting composite material Eu/Tb@Bi-TDPAT by encapsulating Eu(III)/Tb(III) in Bi-TDPAT. In addition, the fluorescence sensing functions of Bi-TDPAT and Bi-TATAB were explored. The results showed that they could detect and recognize various nitrophenols, and the optimal limit of detection is as low as 0.21 µM, which can be reused even after five cycles. Energy competitive absorption (CA) and photo-induced electron transfer are the main sensing mechanisms. By comparing and analyzing the properties of these two bismuth-based crystalline materials, we believe that this work also provides inspiration for the synthesis and development of bismuth-based MOF in the future.

Three-pole wheel paddle luminescent metal organic frameworks (LMOFs) based on the oxygen substituted triazine tricarboxylic acid ligand: recognition and detection of small drug molecules and aromatic amine molecules.

Luminescent metal organic frameworks (LMOFs) are considered to be a type of promising optical sensing material due to their designable and tunable functions, and stable pore structures. Therefore, the preparation of LMOFs has become a research hotspot in recent years. As we know, triazine carboxylic acid ligands are conducive for constructing LMOF materials due to their large π electron conjugated system. In this work, two crystalline materials [Cd3(TCPT)2]·0.5DMF·4H2O (1) and (H3O)[Zn2(TCPT)(µ2-OH)2]·0.5DMF·3H2O (2) were obtained by the reaction of the triazine carboxylic acid ligand 2,4,6-tris(4-carboxyphenoxy)-1,3,5-triazine (H3TCPT), as an extended carboxylate arm, and d10 transition metal salts. Their structures were determined by single crystal X-ray diffraction and characterized by infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV-vis), fluorescence spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TG). The experimental results showed that complexes 1 and 2 show excellent fluorescent emission behavior. Thus, we explored their fluorescence sensing properties. To our delight, the results showed that they both had the ability to sense small organic drug molecules and aromatic amine molecules containing o-phenylenediamine (OPD), m-phenylenediamine (MPD) and p-phenylenediamine (PPD). In general, the practical applications of a MOF material are usually limited because of the relatively harsh synthesis methods. In this aspect, we studied the synthesis method in detail to obtain the optimal reaction conditions for the large-scale synthesis of 1 and 2. The preparation of the two LMOF materials only required about 3 hours of heating time and they could be prepared on a large scale, which is significant for the practical applications of LMOFs.

Stimuli-Responsive Naphthalenediimide Cd-MOFs Tuned by Different Aliphatic Dicarboxylic Acids with Extended Spacers.

A series of novel Cd metal-organic frameworks (MOFs) (1-9) with different extended spacers with seven kinds of the aliphatic dicarboxylic acids as secondary building linkers based on N,N'-di(4-pyridylacylamino)-1,4,5,8-naphthalenediimide (NDI-A) have been designed and synthesized by changing the volume ratio of solvents under solvothermal conditions. In addition, the secondary building linkers of aliphatic dicarboxylic acids have different spacer lengths, resulting in different structures of complexes 1-9. So, their packing structures are affected by the degree of distortion of the NDI-A ligand, the different aliphatic dicarboxylic acids ligands, and the hydrogen-bonding patterns. Complexes 1-9 showed stimuli-responsive emission tuned by different aliphatic dicarboxylic acids with extended length spacers under UV light irradiation, accompanied by the color change from light orange to dark brown, and achieved reversible photochromic under heating, which indicates that they could serve as secret erasable inks. Moreover, complexes 1-9 exhibited selective vaporchromic behavior to methylamine (MA), and the vaporchromic sample could be recovered after washing with MeOH. It is worth noting that the preparation of poly(vinyl alcohol) (PVA)-NDI-MOF films enables the photochromic and vaporchromic properties of complexes 1-9 to apply in practice. In addition, complexes 1-9 exhibited good fluorescence properties as sensing probes toward 2,4,6-trinitrophenol (TNP) with lower limits of detection. In short, this work provides a broad field to explore the creative NDI-MOF materials with photoactive and luminescent properties.

Cu(II) and Zn(II) frameworks constructed by directional tuning of diverse substituted groups on a triazine skeleton and supermassive adsorption behavior for iodine and dyes.

The controllable design, synthesis and functional properties of a series of triazine tetratopic carboxylic MOFs have always been hotspots and challenges for research. Based on the characterization of the C-Cl bond on the triazine skeleton being easily substituted by some functional groups, we designed and synthesized a series of triazine tetratopic carboxylic Cu(II) and Zn(II) MOFs via the reaction of Cu(NO3)2·2.5H2O and ZnSO4·7H2O, as well as triazine tetratopic carboxylic H4TDBA-Cl (H4TBDA-Cl = 5,5'-((6-chloro-1,3,5-triazine-2,4-diyl)bis(azanediyl))diisophthalic acid) under hydrothermal conditions. During the process of synthesizing, the C-Cl bond on the triazine skeleton of the ligand was substituted with different groups, which formed the complexes ([Cu2(TBDA-Cl)(H2O)·10DMF·30H2O]n) (DMF = N,N-dimethylformamide) (1), N(Me)2 -[(CH3)2NH2]4·[Zn3(HTBDA-N)2(SO4)2]n (2) and H ([Cu2(TBDA-H)(H2O)]n) (3), respectively. It is worth noting that the in situ substitution reaction occurred for complexes 2 and 3 during the process of synthesis. Also, the structural analysis showed that the molecules in complexes 1-3 were connected with different building blocks to form different three-dimensional structures. We performed iodine adsorption experiments on the three complexes and found that there was a significant relationship between the structural configuration and adsorption behaviour. The results showed that the complex 1 with the Cl atom on the triazine skeleton could have a boosting effect on adsorption with iodine. It displayed a remarkable adsorption effect for iodine (in the solution of water: 7.6 g g-1 and in the solution of cyclohexane: 548.2 mg g-1). In addition, it also displayed the adsorption effect for JGB dye (204.9 mg g-1). For complex 2, it displayed an uptake effect for iodine in the solution of cyclohexane (529 mg g-1). The possible adsorption mechanism was also investigated. By comparison, we found that chlorine atoms could play an important role in the adsorption processes. The adsorption capacity of complex 1 (containing the chlorine atom in the structure) was much higher than that for complex 3.

Integrated Photoresponsive Alkaline Earth Metal Coordination Networks: Synthesis, Topology, Photochromism and Photoluminescence Investigation.

Photoresponsive materials are a key part of the age of smart technology that have potential in a broad range of applications. Coordination networks (CNs) are widely used due to their designability and stability. In this work, three novel alkaline earth metal coordination networks (AEM-CNs): [Mg(CMNDI)(H2 O)2 ], [Ca(CMNDI)(H2 O)2 ]⋅H2 O, and [Sr(CMNDI)(H2 O)(DMF)] with fsl, cds, and scn topology nets were synthetized via N,N'-bis(carboxymethyl)-1,4,5,8-naphthalenediimide (H2 CMNDI); the scn net is not found in the Reticular Chemistry Structure Resource or ToposPro. The reusable and sensitive photochromic properties of the three CNs enable them to be used as secret inks or ultraviolet detectors. In addition, the CNs also exhibited reusable photoluminescent turn-off toward the drug molecules, balsalazide disodium (Bal.) and colchicine (Col.), with good limits of detection of 0.16 and 0.70 µM. To the best of our knowledge, this is the first study of a fluorescence sensor for Bal. Thus, the AEM-CNs provide a design idea for integrated photoresponsive materials that could be further improved in the near future by further study.