Defect‐Assisted Loading and Docking Conformations of Pharmaceuticals in Metal–Organic Frameworks

Abstract

Understanding of drug-carrier interactions is essential for the design and application of metal-organic framework (MOF)-based drug-delivery systems,a nd such drug-carrier interactions can be fundamentally different for MOFs with or without defects.Herein, we reveal that the defects in MOFs play ak ey role in the loading of many pharmaceuticals with phosphate or phosphonate groups.T he host-guest interaction is dominated by the Coulombic attraction between phosphate/ phosphonate groups and defect sites,a nd it strongly enhances the loading capacity.F or similar molecules without ap hosphate/phosphonate group or for MOFs without defects,t he loading capacity is greatly reduced. We employed solid-state NMR spectroscopyand molecular simulations to elucidate the drug-carrier interaction mechanisms.T hrough as ynergistic combination of experimental and theoretical analyses,t he docking conformations of pharmaceuticals at the defects were revealed.

Unsaturated NiII Centers Mediated the Coordination Activation of Benzylamine for Enhancing Photocatalytic Activity over Ultrathin Ni MOF-74 Nanosheets

“…Generally, the weight ratio can be used to verify the defect degree of samples. 41,47 The magnitude of weight loss signally decreases from NMBs to NMNs, indicating that the linker content in Ni MOF-74 signally decreases and the existence of defects, exactly as expected. Furthermore, the existence of defects also could be further explored by room-temperature electron spin resonance (ESR) spectroscopy.…”

Hierarchically Macro-Microporous Ce-Based MOFs for the Cleavage of DNA

“…Such significant shift of binding energy with 0.8 eV implies that P atoms in the backbone of DNA experience a great extent of electron withdrawal. , This is reasonable since the abundant exposed Ce­(IV)–OH sites of Ce 6 cluster on macroporous walls could strongly coordinate with the P–OH and activate the adjacent phosphodiester bonds of DNA, making them susceptible to be hydrolyzed (Figure C). ,, Meanwhile, the presence of adjacent Ce­(III) sites of Ce 6 cluster might work as synergistic sites to provide a bound hydroxide or water as the nucleophile for the attack of the phosphodiester bonds, which could accelerate the hydrolytic cleavage of DNA. , P nuclear magnetic resonance (NMR) was further conducted to disclose the atomic configuration of adsorbed DNA on HMUiO-66­(Ce). Compared with the 31 P NMR signal of free DNA in solution (Figure B, in blue), a broadened and single signal peaking at −7.55 ppm could be clearly observed for DNA@HMUiO-66­(Ce) (in red), suggesting that only one main coordination conformation is present . Such considerable chemical shift of 31 P NMR signal toward high-field by roughly 6.3 ppm confirms the fact that the P–OH groups of DNA could strongly coordinate with Ce–OH active sites and initiate the hydrolytic cleavage of DNA mainly in a monodentate configuration mode (Figure D). − …”

“…Compared with the 31 P NMR signal of free DNA in solution (Figure B, in blue), a broadened and single signal peaking at −7.55 ppm could be clearly observed for DNA@HMUiO-66­(Ce) (in red), suggesting that only one main coordination conformation is present . Such considerable chemical shift of 31 P NMR signal toward high-field by roughly 6.3 ppm confirms the fact that the P–OH groups of DNA could strongly coordinate with Ce–OH active sites and initiate the hydrolytic cleavage of DNA mainly in a monodentate configuration mode (Figure D). − …”

Structural and Acidic Characteristics of Multiple Zr Defect Sites in UiO-66 Metal–Organic Frameworks

“…Defect engineering in porous metal–organic framework (MOF) materials has attracted widespread attention in recent years − mainly because the resultant structural diversity of pore channels and electronic properties significantly modulates their gas adsorption and separation − and catalytic performances. − This kind of effective regulation strategy to activate the hidden abilities of parent MOFs may be realized through deliberate removal of part of metal nodes or organic linkers. − ,− As one of the most famous MOF materials, the zirconium-based UiO-66 possesses excellent thermal, chemical, and mechanical stabilities due to the strong bonding interactions between central Zr atoms and organic terephthalate linkers, − making it an enormously promising material in various application fields such as catalysis and adsorption. − Typically, the perfect Zr atoms in the nondefective UiO-66 framework are eight-coordinated with the organic linkers, as illustrated in Scheme . However, due to the nearly inevitable missing linker effect during synthesis or postsynthesis, , the structural defects have been discovered to be prevalent inside UiO-66 lattices, which usually play a crucial role in tailoring the material properties. − …”

“…Solid-state NMR spectroscopy has been widely utilized to explore the local chemical structures in various solid materials including MOFs. ,− As shown in Figure c, three signals at 1.5, 2.0, and around 8.0 ppm are observed in the 1 H MAS NMR spectrum of dehydrated UiO-66-150 sample. Among them, the peaks at 1.5 and 2.0 ppm could be ascribed to Zr–OH groups with distinct chemical environment, whereas the broad resonance at around 8.0 ppm mainly arises from the protons in the aromatic rings of organic linkers .…”