Straightforward Synthesis of Single-Crystalline and Redox-Active Cr(II)-carboxylate MOFs

OXA-CuS@UiO-66-NH2 as a drug delivery system for Oxaliplatin to colorectal cancer cells

In this work, UiO-66-NH₂ was used to prepare a new delivery system by incorporating copper sulfide (CuS) into the pores. The CuS nanoparticles (NPs) were prepared to enhance the anticancer effects of Oxaliplatin (OXA) against colorectal cancer. The oxaliplatin was loaded into CuS@UiO-66-NH₂. To characterize and investigate their cytotoxicity effects, powder X-ray diffraction (PXRD), Fourier transformation infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) analysis, UV-Visible analysis, inductively coupled plasma mass spectrometry (ICP-MS), and MTT assay were considered to be performed. According to the observations, the cytotoxicity of OXA-CuS@UiO-66-NH₂ was greater than that of the OXA alone.

Accelerated FeIII/FeII redox cycle of Fenton reaction system using Pd/NH2-MIL-101(Cr) and hydrogen

In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH₂-MIL-101(Cr) was constructed based on H₂ and Pd/NH₂-MIL-101(Cr). The improved system would result in an accelerated reduction in Fe^III, and provide a continuous and fast degradation efficiency of the 10 mg L^-1 4-chlorophenol which was the model contaminant by using only trace level Fe^II. The activity of Pd/NH₂-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH₂-MIL-101(Cr).

Polymorphous Indium Metal-Organic Frameworks Based on a Ferrocene Linker: Redox Activity, Porosity, and Structural Diversity

The metallocene-based linker molecule 1,1'-ferrocenedicarboxylic acid (H₂FcDC) was used to synthesize four different polymorphs of composition [In(OH)(FeC₁₂H₈O₄)]. Using conventional solvent-based synthesis methods and varying the synthetic parameters such as metal source, reaction temperature, and solvent, two different MOFs and one 1D-coordination polymer denoted as CAU-43 (1), In-MIL-53-FcDC_a (2), and In-FcDC (3) were obtained. Furthermore, thermal treatment of CAU-43 (1) at 190 °C under vacuum yielded a new polymorph of 2, In-MIL-53-FcDC_b (4). Both MOFs 2 and 4 crystallize in a MIL-53 type structure, but in different space groups C2/m for 2 and P1̅ for 4. The structures of the four title compounds were determined by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), or a combination of three-dimensional electron diffraction measurements (3D ED) and PXRD. N₂ sorption experiments of 1, 2, and 4 showed specific surface areas of 355 m² g^-1, 110 m² g^-1, and 140 m² g^-1, respectively. Furthermore, the electronic properties of the title compounds were characterized via Mössbauer and EPR spectroscopy. All Mössbauer spectra showed the characteristic doublet, proving the persistence of the ferrocene moiety. In the cases of 1, 3, and 4, appreciable impurities of ferrocenium ions could be detected by electron paramagnetic resonance spectroscopy. Cyclovoltammetric experiments were performed to demonstrate the accessible redox activity of the linker molecule of the title compounds. A redox process of FcDC^2- with oxidation (between 0.86 and 0.97 V) and reduction wave (between 0.69 and 0.80 V) was observed.

Solvent Templating and Structural Dynamics of Fluorinated 2D Cu-Carboxylate MOFs Derived from the Diffusion-Controlled Process

The layered 2D MOFs, owing to their enhanced flexibility and tunability, have recently emerged as a promising alternative to the 3D microporous MOFs in the quest for novel responsive functional materials. However, maintaining the simultaneous control over self-assembly of molecular building blocks as well as ordered stacking of MOF layers poses a significant synthetic challenge. We report on the controlled 2D MOF formation based on a case study of solvent-templated growth of a series of 2D Cu(II)–carboxylate MOFs varying in stacking modes and distances using a diffusion-controlled MOF deposition approach in various solvent mixtures. Moreover, we demonstrate the structural dynamics of the developed 2D MOFs involving both in-plane and out-of-plane movements of the individual 2D layers triggered by solvent exchange, which allowed for selective postsynthetic transformations between the developed 2D MOFs. We also investigated the gas adsorption properties of the developed MOFs, which demonstrates a remarkable crystal size effect on the N₂ adsorption capacity using a model 2D MOF system.

A room temperature diffusion-based approach has been used to prepare a new family of 2D MOFs based on Cu²⁺ paddlewheel clusters and bifunctional fluorinated carboxylate linkers. The stacking distance and geometry of the MOF layers was depending on the solvent mixture used. Remarkably, the developed 2D materials could be postsynthetically transformed into one another by solvent exchange, which was selectively controlled by the type of guest molecules involved.

Prospects for electroactive and conducting framework materials

Electroactive and conducting framework materials, encompassing coordination polymers and metal-organic frameworks, have captured the imagination of the scientific community owing to their highly designable nanoporous structures and their potential applications in electrochromic devices, electrocatalysts, porous conductors, batteries and solar energy harvesting systems, among many others. While they are now considered integral members of the broader field of inorganic materials, it is timely to reflect upon their strengths and challenges compared with 'traditional' solid-state materials such as minerals, pigments and zeolites. Indeed, the latter have been known since ancient times and have been prized for centuries in fields as diverse as art, archaeology and industrial catalysis. This opinion piece considers a brief historical perspective of traditional electroactive and conducting inorganic materials, with a view towards very recent experimental progress and new directions for future progress in the burgeoning area of coordination polymers and metal-organic frameworks. Overall, this article bears testament to the rich history of electroactive solids and looks at the challenges inspiring a new generation of scientists. This article is part of the theme issue 'Mineralomimesis: natural and synthetic frameworks in science and technology'.

The construction of accelerated catalytic Fenton reaction based on Pd/MIL-101(Cr) and H2

A novel catalytic Fenton system based on H₂ and the solid catalyst Pd/MIL-101(Cr) (MHACF-MIL-101(Cr)) was developed at normal temperature and pressure. In this system, the reduction process of Fe^III back to Fe^II was accelerated significantly.

Facile Mechanosynthesis of the Archetypal Zn-Based Metal-Organic Frameworks

Mechanochemical methods have been successful in providing rapid access to a number of inorganic-organic functional materials under mild conditions. Recently, we demonstrated a novel mechanochemical strategy for metal-organic framework (MOF) preparation based on predesigned oxo-centered secondary building units. Herein, we develop this method for the facile preparation of the isoreticular MOF (IRMOF) family members based on a combination of an oxozinc amidate cluster, [Zn₄(μ₄-O)(NHOCPh)₆], and selected ditopic aminoterephthalate and 4,4'-biphenyldicarboxylate as well as tritopic 1,3,5-benzenetribenzoate ligands. The resulting IRMOF-3, IRMOF-10, and MOF-177 crystalline materials were characterized using powder X-ray diffraction, IR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis. We found that the character of the organic linker strongly affects the nature of the resulting MOF crystallites after activation processes. The SEM images demonstrate that IRMOF-3 formed microcrystallites in the range of 400-500 nm, while the two other materials exhibited microstructures of amorphous phases. The porosity of each sample was estimated by N₂ sorption measurements at 77 K. These results provide an efficient and general method for the mechanosynthesis of Zn-based MOF materials using a predesigned oxozinc cluster.