High-Performance Porous Organic Polymers for Environmental Remediation of Toxic Gases.

Sulfur dioxide (SO2) is a harmful acidic gas generated from power plants and fossil fuel combustion and represents a significant health risk and threat to the environment. Benzimidazole-linked polymers (BILPs) have emerged as a promising class of porous solid adsorbents for toxic gases because of their chemical and thermal stability as well as the chemical nature of the imidazole moiety. The performance of BILPs in SO2 capture was examined by synergistic experimental and theoretical studies. BILPs exhibit a significantly high SO2 uptake of up to 8.5 mmol g-1 at 298 K and 1.0 bar. The density functional theory (DFT) calculations predict that this high SO2 uptake is due to the dipole-dipole interactions between SO2 and the functionalized polymer frames through O2S(δ+)···N(δ-)-imine and O═S═O(δ-)···H(δ+)-aryl and intermolecular attraction between SO2 molecules (O═S═O(δ-)···S(δ+)O2). Moderate isosteric heats of adsorption (Qst ≈ 38 kJ mol-1) obtained from experimental SO2 uptake studies are well supported by the DFT calculations (≈40 kJ mol-1), which suggests physisorption processes enabling rapid adsorbent regeneration for reuse. Repeated adsorption experiments with almost identical SO2 uptake confirm the easy regeneration and robustness of BILPs. Moreover, BILPs possess very high SO2 adsorption selectivity at low concentration over carbon dioxide (CO2), methane (CH4), and nitrogen (N2): SO2/CO2, 19-24; SO2/CH4, 118-113; SO2/N2, 600-674. This study highlights the potential of BILPs in the desulfurization of flue gas or other gas mixtures through capturing trace levels of SO2.

Selective Reduction of Multivariate Metal-Organic Frameworks for Advanced Electrocatalytic Cathodes in High Areal Capacity and Long-Life Lithium-Sulfur Batteries.

Lithium-sulfur batteries hold great promise as next-generation high-energy-density batteries. However, their performance has been limited by the low cycling stability and sulfur utilization. Herein, we demonstrate that a selective reduction of the multivariate metal-organic framework, MTV-MOF-74 (Co, Ni, Fe), transforms the framework into a porous carbon decorated with bimetallic CoNi alloy and Fe3O4 nanoparticles capable of entrapping soluble lithium polysulfides while synergistically facilitating their rapid conversion into Li2S. Electrochemical studies on coin cells containing 89 wt % sulfur loading revealed a reversible capacity of 1439.8 mA h g-1 at 0.05 C and prolonged cycling stability for 1000 cycles at 1 C/1060.2 mA h g-1 with a decay rate of 0.018% per cycle. At a high areal sulfur loading of 6.9 mg cm-2 and lean electrolyte/sulfur ratio (4.5 µL:1.0 mg), the battery based on the 89S@CoNiFe3O4/PC cathode provides a high areal capacity of 6.7 mA h cm-2. The battery exhibits an outstanding power density of 849 W kg-1 at 5 C and delivers a specific energy of 216 W h kg-1 at 2 C, corresponding to a specific power of 433 W kg-1. Density functional theory shows that the observed results are due to the strong interaction between the CoNi alloy and Fe3O4, facilitated by charge transfer between the polysulfides and the substrate.

High-Efficacy Hierarchical Dy2O3/TiO2 Nanoflower toward Wastewater Reclamation: A Combined Photoelectrochemical and Photocatalytic Strategy.

Developing a sustainable photocatalyst is crucial to mitigate the foreseeable energy shortage and environmental pollution caused by the rapid advancement of global industry. We developed Dy2O3/TiO2 nanoflower (TNF) with a hierarchical nanoflower structure and a near-ideal anatase crystallite morphology to degrade aqueous rhodamine B solution under simulated solar light irradiation. The prepared photocatalyst was well-characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, diffuse reflectance UV-vis spectra, and X-ray photoelectron spectroscopy. Further analysis was performed to highlight the photoelectrochemical activity of the prepared photocatalysts such as electrochemical impedance spectroscopy, linear sweep voltammetry, photocurrent response, and a Mott-Schottky study. The crystalline Dy2O3/TNF exhibits superb photocatalytic activity attributed to the improved charge transfer, reduced recombination rate of the electron-hole pairs, and a remarkable red-shift in light absorption.

Sulfamic acid incorporated HKUST-1: a highly active catalyst and efficient adsorbent.

Herein we introduce an effective approach for incorporating sulfamic acid (SA) into HKUST-1. The synthesized materials have been characterized using XRD, XPS, BET, FT-IR, SEM, EDX and TEM. The X-ray diffraction pattern of SA@HKUST-1 is analogous to that of parent HKUST-1 in line shape and d-spacing, proving that chemical modification could be obtained without damage to structural solidity. The XPS spectra confirmed successful sulfonation, due to the single S 2p peak being attributable to SO3H groups at 168 eV. Catalytic efficiency was studied for 7-hydroxy-4-methyl coumarin and 3,4-dihydropyrimidinone synthesis and it was found to be highly dependent on the amount of SA loaded over HKUST-1. Moreover, the adsorptive removal activity of some common organic and inorganic pollutants from water has been studied. To fully understand the adsorption process, the effects of initial dye concentration, pH of solution, adsorbent dosage, contact time and temperature on the adsorption process were successfully studied. Under the optimum conditions 10 wt% SA@HKUST-1 was able to reach the maximum adsorption capacity for Pb2+ (298 mg g-1) and Malachite green (290 mg g-1). Hopefully, this will facilitate research on improving the prospective use of MOFs for future applications.