Metalloporphyrin Metal-Organic Frameworks: Eminent Synthetic Strategies and Recent Practical Exploitations

Abstract

The emergence of metal-organic frameworks (MOFs) in recent years has stimulated the interest of scientists working in this area as one of the most applicable archetypes of three-dimensional structures that can be used as promising materials in several applications including but not limited to (photo-)catalysis, sensing, separation, adsorption, biological and electrochemical efficiencies and so on. Not only do MOFs have their own specific versatile structures, tunable cavities, and remarkably high surface areas, but they also present many alternative procedures to overcome emerging obstacles. Since the discovery of such highly effective materials, they have been employed for multiple uses; additionally, the efforts towards the synthesis of MOFs with specific properties based on planned (template) synthesis have led to the construction of several promising types of MOFs possessing large biological or bioinspired ligands. Specifically, metalloporphyrin-based MOFs have been created where the porphyrin moieties are either incorporated as struts within the framework to form porphyrinic MOFs or encapsulated inside the cavities to construct porphyrin@MOFs which can combine the peerless properties of porphyrins and porous MOFs simultaneously. In this context, the main aim of this review was to highlight their structure, characteristics, and some of their prominent present-day applications.

Keywords: (photo-)catalysis; biomimetic; electrochemical utilization; metalloporphyrins; metal–organic frameworks; porphyrins; synthetic strategies.

Figure 1

Representative structure of a metalloporphyrin complex with a porphine ligand core.

Figure 2

Naturally occurred MPs (metalloporphyrins) (A) iron(II)-porphyrin “Heme B in RBCs” to convey oxygen; (B) magnesium(II)-porphyrin “chlorophyll a” needed for plant photosynthesis; (C) cobalt(II)-porphyrin “methylcobalamin (as vitamin B12)” assisted to facilitate nerve system performances; (D) nickel(II)-porphyrin “Cofactor F430” accelerates methanogenesis in methanogenic archaea). Reprinted with permission from [20].

Figure 3

Examples of some of the previously fabricated porphyrin linkers.

Figure 4

Illustrative demonstration of in situ enveloping of metalloporphyrin into ZIF-8 to conjoin CO₂ to epoxide. Reprinted with permission from [49].

Figure 5

Three basic ways of introduction of open metal sites by PSM synthetic routes to MOFs: (a) cationic guests or organic cations exchange (blue balls) with metal cations (red balls); (b) replacement of a hydroxy protons with Li⁺ and Mg²⁺ ions (red balls); (c) chemical reduction of MOM with Li (red balls) and (d) fourth method is a combination of the first two—a collaborative attachment of metal (red balls) chloride (blue ones) salts to anion and cation binding sites. Besides, the sticks and the crescent-shaped bowls attached to sticks are porphyrin-encapsulated inside MOM-11 and cation/anion binding sites. Reprinted with permission from [50].

Figure 6

Comparison of free-base PCN-222/MOF-545 (fb-1). (a) Tetrakis(4-carboxyphenyl)porphyrin linker, H₄TCPP. (b) [Zr6(m3-O)8(O)8]8¢ node. (c) MOF fb-1, shown across the axis a (d) 3D structure of fb-1, depicted along the c axis. For more clarity hydrogen atoms has been omitted. Reprinted with permission from [54].

Figure 7

Molecular architecture of (a) PCN-222, (b) NU-902, and (c) MOF-525. (d–f) Attributed Zr₆-oxo nodes and the linker (e) carboxylate form of Zn − TCPP) are presented on the right, and (g,h) Lewis acid-catalyzed acyl transfer reaction between pyridylcarbinol (PC) and N-Acylimidazole (NAI) performed by Zirconium-Based (Porphinato)zinc(II) MOF. Reprinted with permission from [80].

Figure 8

Fabrication of M@NC (M = Mn and Co) catalysts used for electrocatalysis oxygen reduction reaction in alkaline medium. Reprinted with permission from [59].

Figure 9

Schematic presentation of the construction procedure of NMOF@SF NPs and their practical mechanism for tumor-specific redox chemodynamic therapy (CDT) combined with photodynamic therapy (PDT) created by Fe (III)-TCPP and glutathione (GSH) upon laser irradiation. Reprinted with permission from [65].