Temperature-Controlled Chiral and Achiral Copper Tetrazolate Metal–Organic Frameworks: Syntheses, Structures, and I₂ Adsorption

Four tetrazole-based three-dimensional (3D) metal–organic frameworks (MOFs), {[Cu^II(btz)]·0.5H₂O}_<i>n</i> (<b>1</b>), [Cu^II(btz)]_<i>n</i> (<b>1′</b>), {[Cu^II(btz)]·0.5I₂}_<i>n</i> (<b>1′·0.5I₂</b>), and [Cu^IICu^I₂(btz)₂]_<i>n</i> (<b>2</b>) [H₂btz = 1,5-bis­(5-tetrazolo)-3-oxapentane)], have been successfully obtained and characterized by crystallography. Compound <b>1</b> features a chiral porous framework. The bulk crystallization of <b>1</b> is composed of enantiomers <b>1a</b> (<i>P</i>4₁) and <b>1b</b> (<i>P</i>4₃), which has been demonstrated by the crystal structure analyses of nine crystals of <b>1</b> randomly selected. The Cotton effect displayed in the solid-state circular dichroism spectrum of <b>1</b> is therefore attributed to enantiomeric excess rather than enantiopurity. The completely dehydrated phase of <b>1</b>, that is, <b>1′</b>, can adsorb 0.5 I₂ molecule per formula unit to yield compound <b>1′·0.5I₂</b>, which has been supported by single-crystal X-ray diffraction, elemental analysis, and thermogravimetric analysis. The locations of I₂ in the pores were unambiguously determined, and the interactions between I₂ molecules and the pore structures were investigated. Compound <b>2</b> crystallizes in an achiral <i>C</i>2/<i>c</i> space group. Interestingly, the formations of chiral <b>1</b> and achiral <b>2</b> significantly depend on the reaction temperature. Between 80 and 140 °C, we got compound <b>1</b> as the only product. At 150 °C, both <b>1</b> and <b>2</b> were in coexistence in the final product. From 160 to 180 °C, only compound <b>2</b> was obtained. More interestingly, treatment of the crystals of <b>1</b> or the mixture of <b>1</b> and <b>2</b> obtained at 150 °C in their mother liquor at 170 °C yielded the crystals of <b>2</b> in a single phase

Three-Dimensional Tubular MoS₂/PANI Hybrid Electrode for High Rate Performance Supercapacitor

By using three-dimensional (3D) tubular molybdenum disulfide (MoS₂) as both an active material in electrochemical reaction and a framework to provide more paths for insertion and extraction of ions, PANI nanowire arrays with a diameter of 10–20 nm can be controllably grown on both the external and internal surface of 3D tubular MoS₂ by in situ oxidative polymerization of aniline monomers and 3D tubular MoS₂/PANI hybrid materials with different amounts of PANI are prepared. A controllable growth of PANI nanowire arrays on the tubular MoS₂ surface provides an opportunity to optimize the capacitive performance of the obtained electrodes. When the loading amount of PANI is 60%, the obtained MoS₂/PANI-60 hybrid electrode not only shows a high specific capacitance of 552 F/g at a current density of 0.5 A/g, but also gives excellent rate capability of 82% from 0.5 to 30 A/g. The remarkable rate performance can be mainly attributed to the architecture with synergistic effect between 3D tubular MoS₂ and PANI nanowire arrays. Moreover, the MoS₂/PANI-60 based symmetric supercapacitor also exhibits the excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 124 F/g at a current density of 1 A/g and 79% of its initial capacitance is remained after 6000 cycles. The 3D tubular structure provides a good and favorable method for improving the capacitance retention of PANI electrode