Rational synthesis of a pyridyl-imidazoquinazoline based multifunctional 3D Zn(II)-MOF: structure, luminescence, selective and sensitive detection of Al3+ and TNP, and its semiconducting device application

Fluorescent Sensors Based on Lanthanide-Based Metal-Organic Frameworks via Devices and pH Response

In light of the escalating industrial and environmental pollution, there is a pressing need for the development of novel materials capable of swiftly detecting pollutants. Here, we report the synthesis of five lanthanide metal-organic frameworks sharing a common structure, prepared via a hydrothermal method and denoted as [Ln2(H2DHBDC)2(phen)(H2O)6]n (where CUST-888 corresponds to Tb, CUST-889 corresponds to Eu, CUST-890 corresponds to Gd, CUST-891 corresponds to Dy, and CUST-892 corresponds to Nd). Notably, CUST-888 and CUST-889 exhibit discernible visual alterations in response to acidic and alkaline conditions. To assess their practical utility, luminescent test strips and light-emitting diode lights based on CUST-888 and CUST-889 were devised, enabling the visual detection of luminescence color changes induced by Hg2+, Cr2O72-, tetracycline, and 2,4,6-trinitrophenol. Furthermore, highlighters derived from CUST-888 and CUST-889 were designed, showcasing robust stability, adjustable color, and substantial potential for application in the realm of anticounterfeiting.

Chromone-Based Cd(II) Fluorescent Coordination Polymer Fabricated to Study Optoelectronic and Explosive Sensing Properties

Here, electrical conductivity and explosive sensing properties of multifunctional chromone-Cd(II)-based coordination polymers (CPs) (1-4) have been explored. The presence of different pseudohalide linkers, thiocyanate ions, and dicyanamide ions resulted in 1D and 3D architecture in the CPs. Thin film devices developed from CPs 1-4 (complex-based Schottky devices, CSD1, CSD2, CSD3, and CSD4, respectively) showed semiconductor behavior. Their conductivity values increased under photo illumination (1.37 × 10-5, 1.85 × 10-5, 1.61 × 10-5, and 2.01 × 10-5 S m-1 under dark conditions and 5.06 × 10-5, 8.78 × 10-5, 7.26 × 10-5, and 10.21 × 10-5 S m-1 under light). The nature of the I-V plots of these thin film devices under light irradiation and dark are nonlinear rectifying, which has been observed in Schottky barrier diodes (SBDs). All four CPs (1-4) exhibited highly selective fluorescence quenching-based sensing properties toward well-known explosives, 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP). The limit of detection (LOD) values are 55, 28, 27, and 31 μM for TNP and 78, 44, 32, and 41 μM for DNP for complexes 1-4, respectively. A structure property correlation has been established to explain optoelectronic and explosive sensing properties.

Multi-analyte fluorescence sensing based on a post-synthetically functionalized two-dimensional Zn-MOF nanosheets featuring excited-state proton transfer process

Covalent post-synthetic modification of metal-organic frameworks (MOFs) represents an underexplored but promising avenue for allowing the addition of specific fluorescent recognition elements to produce the novel MOF-based sensory materials with multiple-analyte detection capability. Here, an excited-state proton transfer (ESPT) active sensor 2D-Zn-NS-P was designed and constructed by covalent post-synthetic incorporation of the excited-state tautomeric 2-hydroxypyridine moiety into the ultrasonically exfoliated amino-tagged 2D Zn-MOF nanosheets (2D-Zn-NS). The water-mediated ESPT process facilitates the highly accessible active sites incorporated on the surface of 2D-Zn-NS-P to specifically respond to the presence of water in common organic solvents via fluorescence turn-on behavior, and accurate quantification of trace amount of water in acetonitrile, acetone and ethanol was established using the as-synthesized nanosheet sensor with the detection sensitivity (<0.01% v/v) superior to the conventional Karl Fischer titration. Upon exposure to Fe3+ or Cr2O72-, the intense blue emission of the aqueous colloidal dispersion of 2D-Zn-NS-P was selectively quenched even in the coexistence of common inorganic interferents. The prohibition of the water-mediated ESPT process and local emission, induced by the coordination of ESPT fluorophore with Fe3+ or by Cr2O72- competitively absorbs the excitation energy, was proposed to responsible for the fluorescence turn-off sensing of the respective analytes. The present study offers the attractive prospect to develop the ESPT-based fluorescent MOF nanosheets by covalent post-synthetic modification strategy as multi-functional sensors for detection of target analytes.

Two isostructural Zn/Co-MOFs with penetrating structures: multifunctional properties of both luminescence sensing and conversion of CO2 into cyclic carbonates

Two new metal-organic frameworks (MOFs), namely, {[Zn(HL)(bpea)]·DMF}n (Zn-MOF-1) and {[Co(HL)(bpea)]·DMF}n (Co-MOF-2) (H3L = 3-(3,5-dicarboxybenzyloxy)benzoic acid, bpea = 1,2-di(pyridyl)ethane), were obtained by the reaction of H3L and N-containing ligand bpea with Zn(NO3)2·6H2O and Co(NO3)2·6H2O, respectively. The isomorphic Zn-MOF-1 and Co-MOF-2 featured a 3D penetrating framework with different stabilities, luminescence, and catalytic properties. Luminescence measurement indicated that Zn-MOF-1 could be used to detect Al3+ through a turn-on effect with a detection limit of 0.42 μM. The sensing mechanism experiments showed that the enhanced luminescence of Zn-MOF-1 toward Al3+ may be due to the weak interaction between Al3+ and Zn-MOF-1 and the absorbance-caused enhancement (ACE) mechanism. Meanwhile, both Zn-MOF-1 and Co-MOF-2 showed interesting CO2 adsorption properties and could catalyze the cycloaddition of CO2 to epoxides resulting in 96 and 92% ideal products within 12 hours, respectively. They can be cycled up to 5 times without significant loss of catalytic efficiency.

Correlation in Structural Architecture toward Fabrication of Schottky Device with a Series of Pyrazine Appended Coordination Polymers

Energy is the center of importance for the survivability of civilization. Use of fossil fuel is going to be suspended, and renewable energy is technologically costlier. In the quest for new energy sources and to minimize fuel expenditure, the design of energy efficient devices is one of the solutions. Toward this objective, highly delocalized π-acidic N-hetreocycle pyrazine bridged Cd(II)-based coordination polymers (CPs), [Cd(tppz)(adc)(MeOH)] (1), [Cd(tppz)(trep)] (2), and [Cd(tppz)(2,6-ndc)] (3; tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) are synthesized in combination with π-accessible dicarboxylato linkers (acetylene dicarboxylic acid (H2adc), terephthalic acid (H2trep), and 2,6-naphthalene dicarboxylic acid (2,6 H2ndc)). The structures of the compounds, 1-3, have been confirmed by single-crystal X-ray diffraction measurements. Analysis of electrical property demonstrates that light irradiation enhances the conductivity and follows the order 3 > 2 > 1; compound 3 possesses the highest conductivity (1.93 × 10-3 (light), 1.12 × 10-4 S m-1 dark)), than 2 (1.80 × 10-4 (light), 1.10 × 10-4 S m-1 (dark)) and 1 (5.06 × 10-5 (light), 4.72 × 10-5 S m-1 (dark)). This light-induced electrical conductivity can pave the way toward fabrication of an active electronic device by using the discussed materials.

Coordination polymers: a promising candidate for photo-responsive electronic device application

The design and synthesis of electrically conductive coordination polymers (CPs) are of special interest due to their applications in the fabrication of many environmentally benign emerging technologies, such as molecular wires, photovoltaic cells, light emitting diodes (LEDs), field effect transistors (FETs) and Schottky barrier diodes (SBDs). Owing to their structural flexibility, easy functionality and adjustable energy levels, CPs are promising candidates for providing a better pathway for superior charge transport. Again, the utilization of visible light as an external stimulus to control and manoeuvre the electrical properties of the CPs is exceptionally motivating for the development of many optoelectronic devices, such as photodetectors, photo-switches, photodiodes and chemiresistive sensors. The applications of such materials in devices will solve questions regarding the energy crisis and environmental concerns. This study provides an overview of the recent advances in the development of photo-responsive CPs and the possibility of their application in developing optoelectronic devices. In this regard, a thorough literature survey was performed and the studies related to the fabrication of photosensitive conducting CPs for applications in optoelectronic devices are listed.

In Situ Oxidation of Pyridyl-Dihydrobenzoimidazoquinazoline and the Synthesis of a Highly Luminescent Cd(II) Coordination Polymer: A Promising Candidate for Mutagenic Nitroaromatic Detection and Device Fabrication

Pyridyl-substituted imidazoquinoline, a potent fluorescent framework, is advantageous to architect multifunctional coordination networks for sensing and fabricating emergent electrical conductors. In this work, a Cd(II)-based one-dimensional (1D) coordination polymer (1D CP), [Cd(glu)2(pbiq)2(H2O)]n (1), [H2glu = glutaric acid and pbiq = 4-(6-(pyridin-4-yl)benzo[4,5]imidazo[1,2-c]quinazoline)], has been structurally confirmed by single-crystal X-ray crystallography. The H-bonding and π···π interactions built a three-dimensional (3D) supramolecular structure that strongly emits at 416 nm in acetonitrile suspension. Potentially intrusive nitroaromatics (NAs) and trinitrophenol (TNP) selectively quench the strong emission of 1, and the highest quenching is noted in the case of TNP. A detection limit (limit of detection (LOD)) of 1.51 × 10-7 M for TNP is determined. The band gap (3.31 eV) of 1 recognizes semiconducting behavior, and an electronic device is fabricated. The correlation of current vs voltage (I-V plot) reveals a substantial non-ohmic electrical conductivity of 1 (Λ: 1.10 × 10-5 S m-1) along with a low energy barrier (ΦB: 0.69), and the series resistance (Rs) becomes 6.21 kΩ.