A historical perspective on porphyrin-based metal-organic frameworks and their applications

Abstract

Porphyrins are important molecules widely found in nature in the form of enzyme active sites and visible light absorption units. Recent interest in using these functional molecules as building blocks for the construction of metal-organic frameworks (MOFs) have rapidly increased due to the ease in which the locations of, and the distances between, the porphyrin units can be controlled in these porous crystalline materials. Porphyrin-based MOFs with atomically precise structures provide an ideal platform for the investigation of their structure-function relationships in the solid state without compromising accessibility to the inherent properties of the porphyrin building blocks. This review will provide a historical overview of the development and applications of porphyrin-based MOFs from early studies focused on design and structures, to recent efforts on their utilization in biomimetic catalysis, photocatalysis, electrocatalysis, sensing, and biomedical applications.

Keywords: Biomedical applications; Catalysis; Metal–organic frameworks; Porphyrin; Sensing.

Fig. 1.

Numbers of porphyrin MOF reports found in Web of Science, and porphyrin MOF structures in the Cambridge Structural Database (CSD) from 1991 to 2019. The structural data was obtained from the MOF subset of CSD as of May 2020.

Fig. 2.

Representative molecular structures of porphyrin-based organic linkers for the synthesis of MOFs.

Fig. 3.

Active site (top) and representative catalytic oxidation mechanism (bottom) of cytochrome P450. Adapted with permission from Ref. . Copyright 2012 American Chemical Society.

Fig. 4.

The structure of PCN-222/MOF-545 featuring iron porphyrin sites for catalyzing the oxidation of pyrogallol.

Fig. 5.

The structure of PCN-224 featuring cobalt porphyrin sites for catalyzing CO₂ insertion into expoxide.

Fig. 6.

The structure of Hf-PCN-222(Fe) featuring Fe-porphyrin and Hf₆ sites for the tandem transformation of styrene.

Fig. 7.

Structure of ZJU-18 featuring Mn-nodes and Mn-porphyrin linker sites for the catalytic oxidation of alkylbenzene to ketones.

Fig. 8.

The structure of Al-PMOF featuring Zn-porphyrin sites as photosensitizers for hydrogen evolution.

Fig. 9.

Structure of UNLPF-10 featuring In-porphyrin sites for the photocatalytic oxidation of thioanisole.

Fig. 10.

SEM images of PCN-224(Co) (top) and PCN-224(Co)/MWCNT (bottom). Adapted with permission from ref. . Copyright 2018 Springer Nature.

Fig. 11.

Structure of Cu₂(CuTCPP) featuring Cu₂ nodes and Cu-porphyrin sites for the electrochemical reduction of CO₂ to formate and acetate.

Fig. 12.

A summary of various kinds of sensing mechanisms enabled by porphyrin-based MOFs.

Fig. 13.

Schematic illustration of the sensing of heparin elimination process in live rats using a 2D nanosheet MOF (Zn-TCPP(Fe)). Adapted with permission from ref. . Copyright 2017 American Chemical Society.

Fig. 14.

Schematic illustration of the electrochemiluminescence kinase activity assay using MOF-525 featuring Zn-porphyrin sites. Reproduced with permission from ref. . Copyright 2016 Royal Society of Chemistry.

Fig. 15.

A schematic representation of PDT.

Fig. 16.

The structure of DBP-UiO featuring Hf₆ nodes and porphyrin linkers for the light induced generation of singlet oxygen.

Fig. 17.

A proposed mechanism for the production of ¹O₂ from Cu-TCPP in the absence of externally applied light. Here GSH is glutathione and GSSG is the oxidized form of glutathione.

Fig. 18.

An example of utilizing a MOF (IDOi@TBC-Hf) for synergistic PDT/CBI therapy. Here the CBI therapy (IDOi) is loaded into the pores of TBC-Hf and released upon injection. Reproduced with permission from ref . Copyright 2016, American Chemical Society.