Ani Wang

Novel Hydrogen-Bonding Cross-Linking Aggregation-Induced Emission: Water as a Fluorescent “Ribbon” Detected in a Wide Range

The development of efficient sensors for detection of the water content in a wide detection range is highly desirable for balance in many industrial processes and products. Presented herein are six novel different substituted Schiff base Zn(II) complexes, which exhibit the remarkable capability to detect traces of water in a wide linear range (most can reach 0-94%, v/v), low detection limit of 0.2% (v/v), and rapid response time of 8 s in various organic solvents by virtue of an unusual water-activated hydrogen-bonding cross-linking AIE (WHCAIE) mechanism. As a proof-of-concept, the WHCAIE mechanism is explained well by single X-ray diffraction, absorption spectra, fluorescence spectra, dynamic light scattering, 1H NMR spectra, and theoretical calculations. In addition, the molecules demonstrated their application for the detection of humidity (42-80%). These Schiff base Zn(II) complexes become one of the most powerful water sensors known due to their extraordinary sensitivity, fast response, and wide detection range for water.

A highly sensitive turn-on ratiometric luminescent probe based on postsynthetic modification of Tb3+@Cu-MOF for H2S detection

The fabrication of luminescent materials with lanthanide cations encapsulated within MOF pores is currently of interest because luminescent materials are used in numerous applications. In this study, a distinctive strategy via postsynthetic modification (PSM) of a novel metal–organic framework [Cu(HCPOC)2]n (Cu1) (H2CPOC = 5-(4′-carboxyphenoxy)nicotinic acid) and terbium ions (Tb3+) for sensing hydrogen sulfide (H2S) is reported. The obtained composite Tb3+@Cu1 emits a weak typical Tb3+ ion emission and strong ligand-centred emission. Interestingly, H2S, as a strong electron donor, can strongly enhance the luminescence of Tb3+ through its superior affinity for Cu2+ ions. The composite Tb3+@Cu1 was designed as a luminescent turn-on ratiometric probe for H2S detection, showing high sensitivity and selectivity. The detection limit of Tb3+@Cu1 (1.20 μM) is far below that of Cu1 (13.25 μM). Moreover, a similar ligand, 5-(4′-carboxyphenyl)nicotinic acid (H2CPC), was used to synthesize a fascinating structure, [Cu5(CPC)2(HCPC)2(OH−)4]n (Cu2), which was quite similar to that of the famous semiconductor MoS2, with the advantageous support of an organic linker between layers, and it showed a band gap of 2.45 eV.

(E)-4-Methyl-N-((quinolin-2-yl)ethylidene)aniline as ligand for IIB supramolecular complexes: synthesis, structure, aggregation-induced emission enhancement and application in PMMA-doped hybrid material

Judicious structural design employing 2-quinolinecarboxaldehyde and 4-methylaniline was used to generate the Schiff base ligand (E)-4-methyl-N-((quinolin-2-yl)ethylidene)aniline (L). Five IIB complexes, namely, [ZnLCl2] (1), [ZnL(NO3)2] (2), [ZnL(OAc)2]3 (3), [CdL(OAc)2]3 (4), and [HgLCl2] (5) have been synthesized based on L. Single-crystal X-ray diffraction analysis indicates that complexes 1, 3 and 4 exhibit 3D networks, whereas 2 and 5 form 2D layers and 1D chains, respectively. TD-DFT calculations show a good correlation with the UV-vis absorption assigned to π → π* intraligand transitions. Furthermore, complexes 1-5 displayed strong greenish luminescent emissions (518-524 nm) in the aggregate state but weak emissions in solution (aggregation-induced emission enhancement), which may be due to the existence of C-HCl/O hydrogen bonding and ππ stacking interactions, resulting in restriction of intramolecular rotation (RIR). Variable-concentration 1H NMR studies suggested that the aggregates undergo intramolecular changes in conformation due to intermolecular interactions. Moreover, the emission intensity and lifetime exhibited obvious increases induced by mechanical grinding and temperature reduction, which were also attributed to AIEE properties. Subsequently, complex 1 was incorporated into poly(methyl methacrylate) (PMMA), whereby 1-PMMA exhibited enhanced emission intensity (20-fold increase in comparison with that of 1), which offers opportunities for use in plastic greenhouses to increase leaf photosynthesis.

Research on the Mechanism of Aggregation-Induced Emission through Supramolecular Metal–Organic Frameworks with Mechanoluminescent Properties and Application in Press-Jet Printing

This study investigates the mechanism of AIE in the solid state through supramolecular metal-organic frameworks and mechanoluminescent materials for the first time. Herein, four novel differently substituted Schiff base building blocks, SB1-SB4, exhibit typical AIE properties with various fluorescence emissions from yellow to green. SB1-SB4 are linked through C-H···O hydrogen bonding interactions to construct supramolecular metal-organic frameworks (SMOFs): namely, SMOFSB1-SMOFSB4. Particularly, among these SMOFs, SMOFSB3 is observed to have micropores in the 3D supramolecular structure and exhibits mechanoluminescent properties (grinding). An emission turn-on mechanism occurs with destruction of micropores by grinding and blockage of intramolecular rotations of the methyl and acetonitrile in the micropores, resulting in emission turn-on in SMOFSB3. Single-crystal X-ray structures, powder X-ray diffraction, emission spectra at room temperature, temperature-dependent emission spectra, DFT calculations, and a charge separation hypothesis well demonstrate the emission turn-on mechanism, which is consistent with the mechanism of AIE. More importantly, the molecules demonstrated potential application for press-jet printing.

Hot-Pressing Method To Prepare Imidazole-Based Zn(II) Metal–Organic Complexes Coatings for Highly Efficient Air Filtration

Particulate matters (PMs) air pollution has become a serious environmental issue due to its great threat to human health. Herein, metal-organic complexes PBM-Zn1 and PBM-Zn2 coatings (noted as PBM-Zn-Filter) have been produced by the hot-pressing method on various substrates for the first time. Layer-by-layer PBM-Zn-Filters were also obtained through varying hot-pressing cycles. The obtained PBM-Zn-Filters with high robustness show excellent performance in PMs removal. In particular, benefiting from thelarger conjugation system, micropore structure, lower pressure drop, higher electrostatic potential ζ, and electron cloud exposed metal center of PBM-Zn2 (DFT calculations), PBM-Zn2@melamine foam-4 gives the highest removal rates, PM2.5:99.5% ± 1.2% and PM10:99.3% ± 1.1%, and the removal efficiency for capture PM2.5 and PM10 particles in cigarette smoke were both retained at high levels (>95.5%) after 24 h tests. More importantly, a homemade mask is made up by imbedding the PBM-Zn2@melamine foam-4 into a commercial breathing mask, which shows higher removal efficiency, lower pressure drop, smaller thickness, and higher quality factor than two commercial breathing masks, the PMs removal efficiencies for both PM2.5 and PM10 are 99.6% ± 0.5% and 99.4% ± 0.8%, and acceptable air resistance are demonstrated.

Dual-emissive nanocomposites based on Eu(III) functionalized Cu(I)-coordination polymer for ratiometric fluorescent sensing and integrating Boolean logic operations

The most serious and yet unsolved problems of molecular logic operations consist of how to link molecular events in complex systems into a usable device with specific functions. Herein, a fluorescence system based on a Eu(III)-functionalized Cu(I)-coordination polymer was constructed to recognize and connect multiple components (AA/H2O2, H2S and Fe(II)) for developing dual-emissive (B485 and R616) ratiometric fluorescent sensing and integrating Boolean logic operations. More importantly, we first proposed the H2O2–Eu(III)@Cu-COOH system, which can realize the selective and quantitative detection of AA by fluorescence titration experiments of H2O2 even in the presence of various competitive analytes (e.g. H2S and Fe(II)). To demonstrate the strategy, by self-assembling, oxidizing, and connecting with each other, Eu(III)@Cu-COOH and the analytes achieved elementary logic operations (OR, NOR, AND, XOR, IMP and INH) and integrative logic operation (XOR(INH)–OR) to perform non-arithmetic functions and to analyze two or three analytes in a bio-mimicking environment. Considering its strong molecular recognition, the novel prototypes developed here may have potential applications in the fields of biological computers and intelligent multi-analytes detection systems.

Different conjugated system Cd(II)/Hg(II) Schiff base complexes: Syntheses, supramolecular metal−organic frameworks, luminescent properties and DFT study

Abstract A series of different conjugated systems of 2D/3D supramolecular metal-organic frameworks (SMOFs) are constructed by C/O−H⋯Cl hydrogen bonds and π⋯π interactions. These complexes, [HgL1Cl2] (1), [HgL2Cl2] (2), [HgL3Cl2] (3), [CdL4Cl4]2 (4), and [CdL5Cl2(CH3OH)] (5), have been synthesized and characterized by single-crystal X–ray diffraction, 1H NMR, FT–IR, and EA. The X-ray diffraction analyses reveal that 1 features a 3D supramolecular framework with {44·66} topology structure, while 2, 3, and 5 exhibit 3D 6-connected {412·63} topology structures. Complex 4 shows a two-dimensional layer with 44 topology structure. Based on these varied structures caused by different conjugated system, the emission maximum wavelengths of 1–5 can be tuned in a large range of 492–587 nm. Both electron-donating ability and the conjugated system in general can support λem shift to red direction. In order to have better understanding of electronic transitions of the complexes, a time-dependent DFT study has been performed. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates potential to serve as photoactive materials.

Nitrogen-Doped Microporous Carbons Derived from Pyridine Ligand-Based Metal–Organic Complexes as High-Performance SO2 Adsorption Sorbents

Heteroatom-doped porous carbons are emerging as platforms for gas adsorption. Herein, N-doped microporous carbon (NPC) materials have been synthesized by carbonization of two pyridine ligand-based metal-organic complexes (MOCs) at high temperatures (800, 900, 1000, and 1100 °C). For NPCs (termed NPC-1- T and NPC-2- T, where T represents the carbonization temperature), the micropore is dominant, pyridinic-N and other N atoms of MOC precursors are mostly retained, and the N content reaches as high as 16.61%. They all show high Brunauer-Emmett-Teller surface area and pore volume, in particular, NPC-1-900 exhibits the highest surface areas and pore volumes, up to 1656.2 m2 g-1 and 1.29 cm3 g-1, respectively, a high content of pyridinic-N (7.3%), and a considerable amount of SO2 capture (118.1 mg g-1). Theoretical calculation (int = ultrafine m062x) indicates that pyridinic-N acts as the leading active sites contributing to high SO2 adsorption and that the higher content of pyridinic-N doping into the graphite carbon layer structure could change the electrostatic surface potential, as well as the local electronic density, which enhanced SO2 absorption on carbon edge positions. The results show great potential for the preparation of microporous carbon materials from pyridine ligand-based MOCs for effective SO2 adsorption.

CCDC 1527512: Experimental Crystal Structure Determination

Related Article: Ani Wang, Ruiqing Fan, Yuwei Dong, Yang Song, Yuze Zhou, Jianzong Zheng, Xi Du, Kai Xing, and Yulin Yang|2017|ACS Applied Materials and Interfaces|9|15744|doi:10.1021/acsami.7b01254

CCDC 1527517: Experimental Crystal Structure Determination

Related Article: Ani Wang, Ruiqing Fan, Yuwei Dong, Yang Song, Yuze Zhou, Jianzong Zheng, Xi Du, Kai Xing, and Yulin Yang|2017|ACS Applied Materials and Interfaces|9|15744|doi:10.1021/acsami.7b01254