Modulated Self-Assembly of Catalytically Active Metal–Organic Nanosheets Containing Zr6 Clusters and Dicarboxylate Ligands

Two-dimensional metal–organic nanosheets (MONs) have emerged as attractive alternatives to their three-dimensional metal–organic framework (MOF) counterparts for heterogeneous catalysis due to their greater external surface areas and higher accessibility of catalytically active sites. Zr MONs are particularly prized because of their chemical stability and high Lewis and Brønsted acidities of the Zr clusters. Herein, we show that careful control over modulated self-assembly and exfoliation conditions allows the isolation of the first example of a two-dimensional nanosheet wherein Zr6 clusters are linked by dicarboxylate ligands. The hxl topology MOF, termed GUF-14 (GUF = Glasgow University Framework), can be exfoliated into monolayer thickness hns topology MONs, and acid-induced removal of capping modulator units yields MONs with enhanced catalytic activity toward the formation of imines and the hydrolysis of an organophosphate nerve agent mimic. The discovery of GUF-14 serves as a valuable example of the undiscovered MOF/MON structural diversity extant in established metal–ligand systems that can be accessed by harnessing the power of modulated self-assembly protocols

Inorganic materials in drug delivery

Drug delivery systems are used to carry an active pharmaceutical ingredient (API) in order to improve its properties, for instance enhancing the precision of targeting, protecting it from degradation, or controlling the rate of release. A wide range of inorganic materials can be used to achieve these goals. This chapter will review the key recent developments in this field, with a focus on the four families of materials which have attracted most attention: 3D metal organic frameworks (MOFs), 3D mesoporous silicas (MSNs), 2D layered materials, and 0D inorganic nanoparticles (MNPs). These systems can have a very wide range of physical properties and chemical functionalities. For instance, MOFs and MSNs are porous and thus can offer high drug loadings, while stability varies significantly. MOFs often require functionalisation and protection from rapid degradation prior to cargo delivery, while MSNs and MNPs can persist in vivo. Layered materials also vary widely in stability but can result in effective targeting and extended release profiles. In all cases, the presence of an inorganic species in addition to the API can aid targeting and permit imaging to be performed concomitantly with drug delivery. Post-fabrication functionalisation is also possible, allowing further augmentation of tuning of properties. Inorganic systems thus have huge potential in drug delivery, but there are also very significant barriers to clinical adoption which need to be overcome to allow them to reach their full potential

Modulated self-assembly of hcp topology MOFs of Zr/Hf and the rxtended 4,4′-(Ethyne–1,2–diyl)dibenzoate linker

Careful control of synthetic conditions can enhance the structural diversity of metal-organic frameworks (MOFs) within individual metal-linker combinations. Herein, we show that hcp topology MOFs of both Zr(IV) and Hf(IV), linked by the extended (ethyne–1,2–diyl)dibenzoate linker, can be prepared by modulated self-assembly. The controlled addition of acetic acid and water to solvothermal syntheses is essential to generate these phase pure hcp topology materials, which are characterised experimentally and computationally. The central alkyne unit of the linker can be quantitatively brominated, but this results in partial degradation of the hcp phase, in contrast to the more stable fcu topology analogues. Nevertheless, the MOFs represent new members of the hcp topology isoreticular series showing high crystallinity and porosity, and demonstrate that new materials can be discovered in existing MOF phase spaces through judicious adjustment of key synthetic parameters

Modulated Self-Assembly of Catalytically Active Metal-Organic Nanosheets Containing Zr6 Clusters and Dicarboxylate Ligands.

Publication status: PublishedTwo-dimensional metal-organic nanosheets (MONs) have emerged as attractive alternatives to their three-dimensional metal-organic framework (MOF) counterparts for heterogeneous catalysis due to their greater external surface areas and higher accessibility of catalytically active sites. Zr MONs are particularly prized because of their chemical stability and high Lewis and Brønsted acidities of the Zr clusters. Herein, we show that careful control over modulated self-assembly and exfoliation conditions allows the isolation of the first example of a two-dimensional nanosheet wherein Zr6 clusters are linked by dicarboxylate ligands. The hxl topology MOF, termed GUF-14 (GUF = Glasgow University Framework), can be exfoliated into monolayer thickness hns topology MONs, and acid-induced removal of capping modulator units yields MONs with enhanced catalytic activity toward the formation of imines and the hydrolysis of an organophosphate nerve agent mimic. The discovery of GUF-14 serves as a valuable example of the undiscovered MOF/MON structural diversity extant in established metal-ligand systems that can be accessed by harnessing the power of modulated self-assembly protocols

Post-Synthetic Modification of a Metal-Organic Framework Glass.

Melt-quenched metal-organic framework (MOF) glasses have gained significant interest as the first new category of glass reported in 50 years. In this work, an amine-functionalized zeolitic imidazolate framework (ZIF), denoted ZIF-UC-6, was prepared and demonstrated to undergo both melting and glass formation. The presence of an amine group resulted in a lower melting temperature compared to other ZIFs, while also allowing material properties to be tuned by post-synthetic modification (PSM). As a prototypical example, the ZIF glass surface was functionalized with octyl isocyanate, changing its behavior from hydrophilic to hydrophobic. PSM therefore provides a promising strategy for tuning the surface properties of MOF glasses