Ammonia (NH₃) emissions during agricultural production can cause serious consequences on animal and human health, and it is quite vital to develop high-efficiency adsorbents for NH₃ removal from emission sources or air. Porous metal–organic frameworks (MOFs), as the most promising candidates for the capture of NH₃, offer a unique solid adsorbent design platform. In this work, a series of MOFs with different metal centers, ZnBTC, FeBTC and CuBTC, were proposed for NH₃ adsorption. The metal centers of the three MOFs are coordinated in a different manner and can be attacked by NH₃ with different strengths, resulting in different adsorption capacities of 11.33, 9.5, and 23.88 mmol/g, respectively. In addition, theoretical calculations, powder XRD patterns, FTIR, and BET for the three materials before and after absorption of ammonia were investigated to elucidate their distinctively different ammonia absorption mechanisms. Overall, the study will absolutely provide an important step in designing promising MOFs with appropriate central metals for the capture of NH₃.

Ammonia (NH₃) is a common pollutant mostly derived from pig manure composting under humid conditions, and it is absolutely necessary to develop materials for ammonia removal with high stability and efficiency. To this end, metal–organic frameworks (MOFs) have received special attention because of their high selectivity of harmful gases in the air, resulting from their large surface area and high density of active sites, which can be tailored by appropriate modifications. Herein, two synthetic metal–organic frameworks (MOFs), 2-methylimidazole zinc salt (ZIF-8) and zinc-trimesic acid (ZnBTC), were selected for ammonia removal under humid conditions during composting. The two MOFs, with different organic linkers, exhibit fairly distinctive ammonia absorption behaviors under the same conditions. For the ZnBTC framework, the ammonia intake is 11.37 mmol/g at 298 K, nine times higher than that of the ZIF-8 framework (1.26 mmol/g). In combination with theoretical calculations, powder XRD patterns, FTIR, and BET surface area tests were conducted to reveal the absorption mechanisms of ammonia for the two materials. The adsorption of ammonia on the ZnBTC framework can be attributed to both physical and chemical adsorption. A strong coordination interaction exists between the nitrogen atom from the ammonia molecule and the zinc atom in the ZnBTC framework. In contrast, the absorption of ammonia in the ZIF-8 framework is mainly physical. The weak interaction between the ammonia molecule and the ZIF-8 framework mainly results from the inherent severely steric hindrance, which is related to the coordination mode of the imidazole ligands and the zinc atom of this framework. Therefore, this study provides a method for designing promising MOFs with appropriate organic linkers for the selective capture of ammonia during manure composting.

Effectively regulating the rotary motions of molecular rotors through external stimuli poses a tremendous challenge. Herein, a new type of molecular rotor based on azobenzene-strapped mixed (phthalocyaninato)(porphyrinato) rare earth triple-decker complex Azo-1 is reported. Electronic absorption and 1H NMR spectra manifested the reversible isomerization of the rotor Azo-1 between the trans configuration and the cis configuration. The rotational behavior of phthalocyanine rotator in two configurations were investigated by VT-1H NMR experiments, and the results indicated that the phthalocyanine rotator possessed a smaller rotational energy barrier in the cis isomer than in the trans isomer, which was also supported by DFT calculations. This result demonstrates that the rotation of phthalocyanine rotator in (phthalocyaninato)(porphyrinato) rare earth triple-decker complex can be successfully modulated by photo-isomerization via altering irradiation.

The ubiquitous presence of tetracycline in water sources due to its prevalent usage in antibiotics poses a potential risk to ecosystems and to human health. There is therefore a dire need for efficient methods of tetracycline removal. To this end, we constructed a series of super-small-sized BiVO₄ composites with different loading amounts of 5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt% on SiO₂ support by a hydrothermal–calcination method for efficient photocatalytic degradation of tetracycline. XRD and SEM results revealed that these composites all exhibited good crystallinity and well-dispersed morphologies. Particularly, the 20 wt% BiVO₄@SiO₂ of this series of composites showed superior photocatalytic performance, with 84.1% efficiency in tetracycline degradation, higher than any of its counterparts. This can be explained by its wide light-absorption range and high charge-separation efficiency, as confirmed by UV-Vis absorption spectra and quenched fluorescence spectra. This work offers a new method for the design and construction of tetracycline degradation photocatalysts.