Combining the physical advantages of two-dimensional (2D) inorganic nanosheets and the modular design and programmed structure of metal-organic frameworks (MOFs), 2D MOFs remain at the forefront of functional material research. Despite tremendous efforts, precise control in the synthesis of 2D nonlayered MOFs with predesigned topology for desired applications remains challenging. Success in the bottom-up synthesis of 2D nonlayered MOFs via ligand exchange motivated us to incorporate partial BTC (BTC = 1,3,5-benzenetricarboxylate) ligand dissociation and CO2 capped coordination into the top-down treatment of bulk Cu-BTC MOF, leading to successful conversion of a 3D nonlayered network to a 2D Cu-based topological structure. Notably, a supercritical CO2-containing solvent mixture is employed to provide the desired defect and coordination engineering. Thus, our work introduces a new top-down concept based on modulated synthesis to fabricate high-quality 2D nonlayered MOFs for the first time.

In this paper, Cu-BTC derived mesoporous CuS nanomaterial (m-CuS) was synthesized via a two-step process involving carbonization and sulfidation of Cu-BTC for colorimetric glutathione detection. The Cu-BTC was constructed by 1,3,5-benzenetri-carboxylic acid (H3BTC) and Cu2+ ions. The obtained m-CuS showed a large specific surface area (55.751 m2/g), pore volume (0.153 cm3/g), and pore diameter (15.380 nm). In addition, the synthesized m-CuS exhibited high peroxidase-like activity and could catalyze oxidation of the colorless substrate 3,3\',5,5\'-tetramethylbenzidine to a blue product. Peroxidase-like activity mechanism studies using terephthalic acid as a fluorescent probe proved that m-CuS assists H2O2 decomposition to reactive oxygen species, which are responsible for TMB oxidation. However, the catalytic activity of m-CuS for the oxidation of TMB by H2O2 could be potently inhibited in the presence of glutathione. Based on this phenomenon, the colorimetric detection of glutathione was demonstrated with good selectivity and high sensitivity. The linear range was 1-20 μM and 20-300 μM with a detection limit of 0.1 μM. The m-CuS showing good stability and robust peroxidase catalytic activity was applied for the detection of glutathione in human urine samples.

Adsorptive removal of dyes (e.g., malachite green (MG)) from wastewater using commercially available adsorbents is not significantly efficient. Metal-organic frameworks (MOFs) such as Cu-BTC is considered as an excellent adsorbent in adsorption-separation filed. However, the water instability of Cu-BTC restricts its potential utilization in dye wastewater purification. In this paper, we have developed a novel metal/covalent-organic frameworks (Cu-BTC@TpPa-1) binary composite by solvothermal method. This composite serves as a multifunctional platform for the effective removal of MG from water. This Cu-BTC@TpPa-1 obviously keeps structural integrity soaked in water for 7 days. And its heat resistant performance can achieve 360 °C because of the TpPa-1 protection, which is outdistance to that of Cu-BTC. The adsorbed capacity of MG over Cu-BTC@TpPa-1 is exceptionally high, with an uptake of up to 64.12 mg/g, which is superior compared to previous adsorbents, highlighting its superior adsorption capabilities. The adsorptive performance was controlled by the associative effects of Cu-BTC and TpPa-1 with an association effect of π-complexation and electrostatic attraction. The Cu-BTC@TpPa-1 might be a prospective adsorbent for MG capture from industrial wastewater.

Erythromycin, a commonly used macrolide antibiotic, plays a crucial role in both human medicine and animal husbandry. However, its abuse has led to residual presence in the environment, with problems such as the emergence of resistant bacteria and enrichment of resistance genes. These issues pose significant risks to human health. Thus far, there are no effective, environmentally friendly methods to manage this problem. Enzymes can specifically degrade erythromycin without causing other problems, but their unrecyclability and environmental vulnerability hinder large-scale application. Enzyme immobilization may help to solve these problems. This study used Cu-BTC, a synthetic metal-organic framework, to immobilize the erythromycin-degrading enzyme EreB. The loading temperature and enzyme quantity were optimized. The Cu-BTC and EreB@Cu-BTC were characterized by various methods to confirm the preparation of Cu-BTC and immobilization of EreB. The maximum enzyme loading capacity was 66.5 mg g-1. In terms of enzymatic properties, immobilized EreB had improved heat (25-45 °C) and alkaline (6.5-10) tolerance, along with greater affinity between the enzyme and its substrate; Km decreased from 438.49 to 372.30 mM. Recycling was also achieved; after 10 cycles, 57.12% of the enzyme activity was maintained. After composite degradation, the antibacterial activity of erythromycin-containing wastewater was examined; the results showed that the novel composite could completely inactivate erythromycin. In summary, Cu-BTC was an ideal carrier for immobilization of the enzyme EreB, and the EreB@Cu-BTC composite has good prospects for the treatment of erythromycin-containing wastewater.

Isoreticular bimetal M-Cu-BTC has considerable potential in improving the sulfides removal performance of Cu-BTC. Herein, three transition metals, namely, Zn2+, Ni2+ and Co2+, were assessed to fabricate M-Cu-BTC, a desirable isoreticular bimetal. Results demonstrated the feasibility of using Zn2+ to fabricate an isoreticular bimetallic Zn-Cu-BTC. The Zn2+ doping content of Zn-Cu-BTC was varied to investigate its influence on the hydrogen sulfide (H2S) and methyl sulfide (CH3SCH3) removal performance of Cu-BTC. The experimental results indicated that the sulfides removal performance of Zn-Cu-BTC increased and then decreased with increasing Zn doping content. The highest H2S and CH3SCH3 removal capacities of 84.3 and 93.9 mg S/g, respectively, were obtained when the Zn2+ doping content was 17%. The hybridisation of Zn and Cu in Zn-Cu-BTC induced a strong interaction between them. This interaction increased the binding energies of H2S and CH3SCH3 towards the Cu and Zn adsorption sites while weakening the bond order between Zn and Cu. The weakened bond order made the Zn-Cu bonds easier to form metal sulfides during desulfurization process, thereby synergistically enhancing sulphide removal.

Selective oxidation of methane to organic oxygenates over metal-organic frameworks (MOFs) catalysts at low temperature is a challenging topic in the field of C1 chemistry because of the inferior stability of MOFs. Modifying the surface of Cu-BTC via hydrophobic polydimethylsiloxane (PDMS) at 235 °C under vacuum not only can dramatically improve its catalytic cycle stability in a liquid phase but also generate coordinatively unsaturated Cu(I) sites, which significantly enhances the catalytic activity of Cu-BTC catalyst. The results of spectroscopy characterizations and theoretical calculation proved that the coordinatively unsaturated Cu(I) sites made H2O2 dissociative into •OH, which formed Cu(II)-O active species by combining with coordinatively unsaturated Cu(I) sites for activating the C-H bond of methane. The high productivity of C1 oxygenates (CH3OH and CH3OOH) of 10.67 mmol gcat.-1h-1 with super high selectivity of 99.6% to C1 oxygenates was achieved over Cu-BTC-P-235 catalyst, and the catalyst possessed excellent reusability.

The removal of NO has always been a hot issue in the treatment of coal-fired flue gas. In this paper, a hydrothermal synthesis method was used to prepare porous denitration catalysts with polycarboxyl organic isomers (trimellitic acid, phthalic acid, and benzoic acid). And then developed as the NO removing catalysts for low temperature selective catalytic reduction (SCR) with NH3. XRD, BET, SEM, FTIR, XPS, Raman, H2-TPR, NH3-TPD and TG were used to analyze the crystallinity, microscopic morphology, surface functional groups and metal content. The results showed that: (1) From the crystal structure analysis, the catalyst prepared with 1,3,5 and 1,2,4-benzenetricarboxylic acid as ligands (1,3,5-A and 1,2,4-B) was Cu-BTC. (2) 1,3,5-A catalyst had a huge specific surface area, up to 1421.32 m2/g, and a pore volume up to 0.5798 cm3/g. (3) The prepared catalysts were applied to NH3-SCR denitration, and the catalyst with Cu-BTC structure had relatively high catalytic performance, and the overall catalytic capacity showed an increasing trend with the temperature. (4) 1,3,5-A catalyst had stability and catalytic activity. When the temperature was 270 °C, the denitration efficiency reached 83.87%. And within 8 h, the denitration efficiency was stable up to 82%.

Malachite green (MG) has been widely used for controlling external fungi and parasites in the aquaculture. However, MG has been proven to be very hazardous, and the detection of MG in aquaculture environment is crucial for determining whether MG has been used within the allowed limit and for protecting the environment. Herein, a kind of copper based metal-organic frameworks (MOFs) was prepared using copper nitrate and 1,3,5-benzenetricarboxylic acid (H3BTC) as raw materials. The prepared Cu-BTC materials provide larger active area and higher accumulation capacity for MG, and meanwhile lower the charge-transfer resistance. As a result, the oxidation signal and detection sensitivity of MG are significantly improved by Cu-BTC frameworks. The linear range is 2-500 nM, and the detection limit is 0.67 nM, which is much lower than the reported values. Moreover, other usually-used aquaculture drugs have no interferences, including erythromycin, chloramphenicol, oxytetracycline, furazolidone and nitrofurazone. This method was applied in the water samples, and the results were consistent with those using high-performance liquid chromatography.

[This corrects the article DOI: 10.3389/fchem.2020.00129.].

In the present study, metal-organic framework Cu-BTC-supported Sn (II)-substituted Keggin heteropoly nanocomposite (Sn1.5PW/Cu-BTC) was successfully prepared by a simple impregnation method and applied as a novel nanocatalyst for producing biodiesel from oleic acid (OA) through esterification. The nanocatalyst was characterized by Fourier transform infrared spectrometry (FTIR), wide-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption, thermogravimetrics (TG), and NH3-temperature-programmed desorption (NH3-TPD). Accordingly, the synthesized nanocatalyst with a Sn1.5PW/Cu-BTC weight ratio of 1 exhibited a relatively large specific surface area, appropriate pore size, and high acidity. Moreover, an OA conversion of 87.7% was achieved under optimum reaction conditions. The nanocatalyst was reused seven times, and the OA conversion remained at more than 80% after three uses. Kinetic study showed that the esterification reaction followed first-order kinetics, and the activation energy (E a ) was calculated to be 38.3 kJ/mol.