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MOFs with semiconducting behavior exhibit unique optoelectronic properties, and they are hailed as future low-bandgap materials, which are expected to serve as a new generation of functional materials to solve some thorny problems in the field of environment and energy. In this work, eight semiconducting MOFs with chemical formulae, {[Cd(m-bix)(ATP)]}n (1), {[Zn2(m-bix)(ATP)2]·DMF}n (2), {[Cd(m-bix)(BDC)(H2O)]}n (3), {[Co2(m-bix)(BDC)2(H2O)3]·2H2O·CH3OH}n (4), {[Ni2(m-bix)(BDC)2(H2O)3]·2H2O·CH3OH}n (5), {[Cd(m-bix)(Cl)]}n (6), {[Zn(m-bix)(CO3)]}n (7), and {[Cd(FDC)(H2O)3]·2H2O}n (8) (m-bix = m-bis(imidazol-1-ylmethyl)benzene; H2ATP = 2-aminoterephthalic acid; H2BDC = p-phthalic acid; H2FDC = 2,5-furandicarboxylic acid), were successfully synthesized by hydrothermal techniques. Comprehensive characterization of the as-synthesized MOFs showed that they display interesting topologies and fascinating structures (of 6 and 8 being 1D, 1, 2, 3, and 7 being 2D and 4 and 5 being 3D). The incorporation of π-conjugated ligands and abundant intermolecular hydrogen bonds endows these MOFs with higher carrier transport rates, resulting in unique optoelectronic properties. The optical band gaps of MOFs 1–8 obtained by UV reflection spectroscopy were 2.86, 2.59, 3.91, 3.01, 3.69, 3.19, 3.09, and 3.87 eV, respectively, proving that they are all potential semiconductor materials. Electrochemical oxygen evolution reaction (OER) catalysis studies revealed that MOFs 4–5 are efficient catalysts for the OER process with lower overpotentials of 381 and 397 mV at 10 mA cm−2 and lower Tafel slopes of 75.1 and 74.4 mV dec−1. Photoluminescence studies demonstrated that the Cd-based and Zn-based MOFs, especially MOF 2, exhibit strong violet light emission properties in the range of 405–446 nm, which are expected to be used in the development of new luminescent materials. In addition, the photocatalytic performance of these MOFs was evaluated. Among them, the best photocatalytic performance of 4 and 6 was attributed to the combination of the band gap value and luminescence performance, resulting in more photogenerated carriers and thus more catalytically active sites. This work not only provides a certain theoretical and experimental basis for further research on the optoelectronic properties of MOFs, but also affords an advanced strategy for the development of novel multifunctional materials to solve real-life environmental and energy problems. [ABSTRACT FROM AUTHOR]

In order to solve the problems of environmental pollution and energy crisis, it is of great significance to develop low-cost, high-efficiency and environmentally friendly multifunctional materials to deal with environmental and energy concerns. Herein, two multifunctional Cu(II) coordination complexes with the formula {[Cu(m-bix)(FDC)(H2O)]·H2O}n (1) and {[Cu2(DAP)4(NIP)2]·DMF}n (2) (m-bix = m-bis(imidazol-1-ylmethyl)benzene; DAP = N-(4-pyridyl)dimethylamine; H2FDC = 2,5-furandicarboxylic acid; H2NIP = 5-nitroisophthalic acid) were successfully constructed by using mixed ligands via a solvothermal method. Structural analyses show that both complexes exhibit a 1D chain structure, extending into a 3D supramolecular network via abundant hydrogen bonding forces. Electrochemical oxygen evolution reaction (OER) catalytic studies reveal that 1 and 2 are efficient electrocatalysts for the OER. In particular, 2 has a lower overpotential of 360 mV at 1 mA cm−2 under alkaline conditions. Furthermore, both complexes exhibit excellent photocatalytic activity due to their narrow band gaps – 2.51 eV (494 nm) for 1 and 2.77 eV (448 nm) for 2. The oxidation system composed of the complex and H2O2 can degrade methyl orange azo dyes (40 mg L−1) to less than 10% in only 150 minutes under sunlight irradiation. This work demonstrates that employing mixed ligands is a promising approach to obtain multifunctional complexes. It also opens up a unique path for the development of high-efficiency, low-cost, and environmentally friendly multifunctional materials to address environmental and energy issues. [ABSTRACT FROM AUTHOR]

The exothermic efficiency of microwave heating an electrolyte/water solution is remarkably high due to the dielectric heating by orientation polarization of water and resistance heating by the Joule process occurred simultaneously compared with pure water. A three-dimensional finite element numerical model of multi-feed microwave heating industrial liquids continuously flowing in a meter-scale circular tube is presented. The temperature field inside the applicator tube in the cavity is solved by COMSOL Multiphysics and professional programming to describe the momentum, energy and Maxwell's equations. The evaluations of the electromagnetic field, the temperature distribution and the velocity field are simulated for the fluids dynamically heated by single- and multi-feed microwave system, respectively. Both the pilot experimental investigations and numerical results of microwave with single-feed heating for fluids with different effective permittivity and flow rates show that the presented numerical modeling makes it possible to analyze dynamic process of multi-feed microwave heating the industrial liquid. The study aids in enhancing the understanding and optimizing of dynamic process in the use of multi-feed microwave heating industrial continuous flow for a variety of material properties and technical parameters. [ABSTRACT FROM AUTHOR]