Construction of flexible metal-organic framework (MOF) papers through MOF growth on filter paper and their selective dye capture

Competitive formation between 2D and 3D metal-organic frameworks: insights into the selective formation and lamination of a 2D MOF

The structural dimension of metal-organic frameworks (MOFs) is of great importance in defining their properties and thus applications. In particular, 2D layered MOFs are of considerable interest because of their useful applications, which are facilitated by unique structural features of 2D materials, such as a large number of open active sites and high surface areas. Herein, this work demonstrates a methodology for the selective synthesis of a 2D layered MOF in the presence of the competitive formation of a 3D MOF. The ratio of the reactants, metal ions and organic building blocks used during the reaction is found to be critical for the selective formation of a 2D MOF, and is associated with its chemical composition. In addition, the well defined and uniform micro-sized 2D MOF particles are successfully synthesized in the presence of an ultrasonic dispersion. Moreover, the laminated 2D MOF layers are directly synthesized via a modified bottom-up lamination method, a combination of chemical and physical stimuli, in the presence of surfactant and ultrasonication.

A novel monolith ZnS-ZIF-8 adsorption material for ultraeffective Hg (II) capture from wastewater

A novel monolithic adsorption material (ZnS-ZIF-8) was well prepared by means of the functionalized filter paper and explored for Hg (II) capture in wastewater in this work. The novel monolith ZnS-ZIF-8 displayed outstanding capture efficiency toward Hg (II) in the solution containing competitive diverse metal ions within very short time. The adsorption behavior was well fitted with the Langmuir adsorption model and the maximum adsorption capacities for Hg (II) removal was up to 925.9 mg/g. The Hg (II) captured by ZnS-ZIF-8 can be reclaimed by elution with Na₂S solution. The approach of this novel monolith adsorption material displayed the advantages of rapidity, simplicity, selectivity and could be expected to the development of a rapid and efficient device to purify Hg (II) from wastewater in form of the integration filter-adsorption column.

Facile Method To Prepare a Novel Biological HKUST-1@CMCS with Macroscopic Shape Control for the Long-Acting and Sustained Release

We have developed a green and versatile method to prepare hierarchically porous Cu₃(BTC)₂@carboxymethyl chitosan (HKUST-1@CMCS) with a macroscopic shape control and designable performance via the cross-linking of Cu(II) ions with CMCS. Furthermore, atomic force microscopy, scanning electron microscopy, powder X-ray diffraction, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy analyses showed that the morphology of HKUST-1 could be controlled and changed by tailoring the surface roughness ( R_q) of polymer matrix. For the ball-like, fiberlike, and membrane-like composites, the matrix R_q values were 887, 88.4, and 18.2 nm and the average sizes of HKUST-1 crystals were about 10.2, 5.9, and 1.7 μm, respectively. It was found that the larger the R_q of the polymer matrix, the higher the drug payload. The results of drug release showed that the release percentage of dimethyl fumarate from HKUST-1@CMCS was 66% in 326 h, whereas that of Cu@CMCS was only 12 h. Obviously, the HKUST-1@CMCS had a long-acting and sustained release property compared to that of Cu@CMCS due to its complementary advantages of metal-organic frameworks (MOFs) and polymers. Therefore, this study not only provided an interesting way to make up for the shortcomings of MOFs and natural polymer but also developed a long-acting delivery system for a huge potential application prospect.

Highly Transparent, Flexible, and Mechanically Strong Nanopapers of Cellulose Nanofibers @Metal-Organic Frameworks

Freestanding nanopapers were fabricated by the assembly of metal-organic frameworks (MOFs) onto cellulose nanofibers (CNFs). The CNFs are wrapped by continuously nucleated MOF layers (CNF@MOF) by interfacial synthesis, with the charge density on the surface of the CNFs and the dosage of the surfactant polyvinylpyrrolidone (PVP) being carefully adjusted. The obtained CNF@MOF nanofibers with long-range, continuous, hybrid nanostructures were very different to the composites formed by aggregation of MOF nanoparticles on the substrates. Four typical MOFs (HKUST-1, Al-MIL-53, Zn-MOF-74, ZIF-CO₃ -1) were successfully grown onto CNFs in aqueous solutions and further fabricated into freestanding nanopapers. Because of their unique nanostructures and morphologies, the corresponding flexible nanopapers exhibit hierarchical meso-micropores, high optical transparency, high thermal stability, and high mechanical strength. A proof-of-concept study shows that the CNF@MOF nanopapers can be used as efficient filters to separate volatile organic compounds (VOCs) from the air. This work provides a new path for structuring MOF materials that may boost their practical application.

Unbalanced MOF-on-MOF growth for the production of a lopsided core–shell of MIL-88B@MIL-88A with mismatched cell parameters

Atypical unbalanced MOF-on-MOF growth is demonstrated for the production of a lopsided core–shell of MIL-88B@MIL-88A with mismatched cell parameters.

Efficient Capture of Organic Dyes and Crystallographic Snapshots by a Highly Crystalline Amino-Acid-Derived Metal-Organic Framework

The presence of residual organic dyes in water resources or wastewater treatment systems, derived mainly from effluents of different industries, is a major environmental problem with no easy solution. Herein, an ecofriendly, water-stable metal-organic framework was prepared from a derivative of the natural amino acid l-serine. Its functional channels are densely decorated with highly flexible l-serine residues bearing hydroxyl groups. The presence of such a flexible and functional environment within the confined environment of the MOF leads to efficient removal of different organic dyes from water: Pyronin Y, Auramine O, Methylene Blue and Brilliant Green, as unveiled by unprecedented snapshots offered by single-crystal X-ray diffraction. This MOF enables highly efficient water remediation by capturing more than 90 % of dye content, even at very low concentrations such as 10 ppm, which is similar to those usually found in industrial wastewaters. Remarkably, the removal efficiency is improved in simulated contaminated mineral water with multiple dyes.

Design and preparation of metal-organic framework papers with enhanced mechanical properties and good antibacterial capacity

In this study, a biodegradable paper-based composite with good mechanical and antibacterial properties was obtained by first reinforcing the cotton pulp-based paper with carboxylated cellulose nanofiber (CNF) via the Williamson reaction, followed by in situ generating zeolitic imidazolate framework-67 (ZIF-67) nanoparticles on the surface of the resulting cellulosic material. The mechanical properties and antibacterial activities of the resulting composite were investigated. The tensile testing demonstrated that the composites prepared with 2.5 wt% CNF exhibited outstanding mechanical performance under dry and wet conditions with the tensile strength values of 17.20 and 1.90 MPa, respectively, approximately 1.3 and 11 times higher compared to that of the original cellulose paper. Furthermore, the antibacterial experiments showed that the composites exhibited significant bacteriostasis, and the antibacterial properties increased significantly with increasing ZIF-67 loading in the composites. Consequently, this biodegradable composite could be potentially used in the field of medical and health security.