Porphyrinic metal-organic frameworks for biological applications

This review is led by Dr. Xiu-Ping Yan (State Key Laboratory of Food Science and Technology, Jiangnan University).

Natural porphyrins are vital molecules participating in many biological processes. Numerous numbers of porphyrin, metallporphyrin, and their derivatives have been synthesized as catalysts, electron-transporting materials, DNA-binding or cleavage agents, photoluminescence molecules, and photosensitizers. However, the poor solubility and self-aggregation of porphyrins in aqueous solution immensely limit their direct applications due to the strong π-π interaction between planar polyaromatic macrocycles.

Metal-organic frameworks (MOFs) are a family of crystalline porous materials constructed from metal ions/clusters and organic linkers. MOFs with the advantages of high porosity, tunable structure, large surface area, and versatile functionality show extraordinary talents in many important applications, such as gas storage and separation, adsorption, catalysis, conduction, sensing, and biomedical fields. A great deal of attention has been paid toward porphyrin-containing MOFs. In this respect, the number of publications is continually on the rise and their citation number has already exceeded 16,000 by the end of 2021 according to Web of Science.

Porphyrinic metal-organic frameworks (PMOFs), a crucial subclass of MOFs with metal ions/clusters and porphyrins or metallporphyrins as linkers and/or ligands can overcome the limitations of free porphyrin molecules in physiological environment. The native biocompatible properties and the ability of porphyrins and metallporphyrins endow PMOFs great potential in biological applications. A great number of comprehensive reviews have summarized porphyrin-based MOFs and their promising applications. Among porphyrin-based MOFs, the porphyrin@MOFs derived by loading porphyrins into MOF channels and decorating porphyrins on the MOF surface have been described in a previously reported review. Thus, they are not considered here. The PMOFs using porphyrins as ligands and/or linkers can form several possible frameworks with a large scale of metal ions that are noteworthy and most studied. Although previous researches by Chen et al. have summarized the related research on porphyrin-based MOFs for biomedical applications, their focus was not on pure PMOFs, and the application aspects only referred to biosensing, imaging, and therapy. Other applications of PMOFs, such as biomimetic/catalysis and antimicrobial action, have been extensively studied but rarely summarized in a review literature. Therefore, this review would shed light on the research progress in the synthesis and the related biological applications based on PMOFs.

Usually, from a materials science point of view, people would expect the definition of description and an overview of different synthetic approaches to obtain PMOFs. For example, PMOFs were obtained using microwave heating, ultrasound treatment, room temperature synthesis, based on the source of the driven energy responsible for MOF nucleation and growth. Nevertheless, most of the reported PMOFs were synthesized using a solvothermal method. Other synthesized methods such as "room temperature synthesis", "surfactant-assisted approach," and "layer-by-layer growth" were also described in 2.4. In this review, assembly strategies to create PMOFs from the construction point of view were highlighted, especially on the demand for biological applications. Particular properties, such as chemical and water stability, light-harvesting performance, photocatalytic/photosensitive activity in favor of biological applications, are the focus to discuss, providing guidance in structural design and property enhancement for broad applications. A variety of biological applications based on pristine and modified PMOFs were overviewed, inspiring more attention and effort for this prospective direction. Moreover, the opportunities and challenges of PMOFs as promising materials for biological applications were also discussed.

See the article:

Porphyrinic metal-organic frameworks for biological applications

https://doi.org/10.1016/j.asems.2022.100045