Correction to “Review on Metal–Organic Framework Classification, Synthetic Approaches, and Influencing Factors: Applications in Energy, Drug Delivery, and Wastewater Treatment”

In the original review, it was observed that there are inaccuracies in the description of specific concepts and presentation of the materials in the context of MOF chemistry. We apologize for the oversight and have included the corrections below for a better and more accurate understanding of the field.

Text in the Original Manuscript (Section 1, Paragraph 3)

MOFs comprise both organic and inorganic components. The organic components (bridging ligands/linkers) include a conjugate base of a carboxylic acid or anions, such as organophosphorus compounds, salts of sulfonic acid, and heterocyclic compounds as shown in Figure 2. The inorganic elements are metal ions or clusters called secondary building units (SBUs).⁸ The geometry of the MOFs is considered through ligancy, the analytic geometry of the inorganic components (metal ions), and the organic functional group character. MOFs have been shown to include a variety of shapes, including triangles with three points, square paddle wheels with four points, trigonal prisms with six points, and octahedrons with six points as shown in Figure 3. On a basic level, the organic linker (ditopic, tritopic, tetratopic, or multitopic ligands) responds to the metal ion by means of more than one labile or vacant position. The ultimate framework is reigned over via both the metal ion and the primary building unit (PBU).²

Figure 3.

(a) Constructions of typical coordination polymers/MOFs using metal ions or metal ligand fragments and ligands. Reprinted with permission from ref 3a. Copyright 2010 Royal Society of Chemistry and From ref 3b. Copyright 2017 American Chemical Society. (b) Representation of four kinds of MOF superstructures including 0D, 1D, 2D, and 3D MOFs. Reprinted with permission from ref 3. Copyright 2014 Royal Society of Chemistry.

Corrected Text As Follows

It is well-known that MOFs are formed by connecting metal nodes (metal ions or metallic clusters) with organic ligands (ditopic, tritopic, tetratopic, or multitopic ligands) as linkers (Figure 2) via coordination bonds, favoring to form network structures with different dimensions including 0-, 1-, 2-, and 3-dimensional (D) structures of MOFs.^2,3Figure 3a displays the constructions of typical coordination polymers/MOFs using metal ions or metal ligand fragments and ligands.^3a,b Furthermore, to control the physical form of MOFs, significant efforts have been made by several researchers for constructing complex MOF architectures, which favors the creation of orderly MOFs at a macro-/mesoscopic scale with different dimensions (0D, 1D, 2D, and 3D MOF superstructures) (Figure 3b).³ It was also stated that hierarchically structured MOFs can be classified into four kinds such as 0D MOF (hollow microspheres or capsules), 1D MOF (nanotubes, nanofibers, nanorods, nanowires, and etc.), 2D MOF (membranes, thin films, and etc.), and 3D MOF (hierarchically porous continuous and extended systems), respectively. Importantly, the structures of MOFs (network topology) can be dependent on the node and net connectivity. In uninodal types of 3D MOF structures, different geometry of nodes such as 3-connected (trigonal, p = 3), 4-connected (tetrahedral and square planar, p = 4), 5-connected (trigonal bipyramidal, p = 5), 6-connected (octahedral, p = 6), 8-connected (cubic, p = 8), and other higher geometries (p = 10, p = 12) was noticed, whereas binodal structures of 3D MOFs exhibited two geometrically different nodes such as trigonal–tetrahedral, trigonal–square planar, square planar–tetrahedral, trigonal–octahedral, tetrahedral–octahedral, octahedral–trigonal prism, and tetrahedral–cubic, respectively.^3c Reports on MOFs demonstrated that the degree of tunability in the MOF structure greatly depends on the geometry of metal coordination (PBUs), the configuration of metal clusters (SBUs), and metal–ligand coordination chemistry, revealing that the fabrication of new MOFs with different structural characteristics continues unabated, which enhances their enticing opportunities in multidisciplinary research areas.

Revised Figure 3

Figure 3 has been revised as given below.

Text in the Original Manuscript (Section 2.1.1)

Isoreticular MOFs are synthesized by [Zn₄O]⁶⁺ SBU and a series of aromatic carboxylates. They are octahedral microporous crystalline materials. In recent years, for the advancement of sensors, IRMOF-3 has been used abundantly. Zhu and co-workers synthesized nanosheets of IRMOF-3 with magnificent sensitivity and selectivity toward the recognition of 2,4,6-trinitrophenol in wastewater.^20,21

Revised Text As Follows

Isoreticular MOFs

Isoreticular metal–organic frameworks (IRMOFs) are a subset of MOFs characterized by having the same underlying topology but varying in their pore size and functionality. The term “isoreticular” means having the same net or framework structure where building units are connected by covalent bonds. Omar M. Yaghi’s group first successfully synthesized a new class of MOF using octahedral Zn–O–C clusters and ditopic carboxylates as linkers, leading to the formation of reticulate primitive cubic structures with exceptionally rigid and high pore volumes, which was named as “IRMOF”.²⁰ Interestingly, it was noticed that the physicochemical properties of IRMOFs are significantly varied due to the chemical versatility and structural tailorability, thereby extending their applications in catalysis, sensing, adsorption, gas separation, and storage.^20a–c Mai and Liu reviewed synthetic strategies and applications of IRMOFs and summarized the pore volumes and surface areas of IRMOFs (IRMOF-1, IRMOF-3, IRMOF-6, IRMOF-8, IFMOF-11, and IRMOF-18) and other MOFs.^20a Importantly, IRMOFs acted as keen optical and electrochemical sensors for the detection of multiple target analytes. For example, Zhu and co-workers synthesized nanosheets of IRMOF-3 with magnificent sensitivity and selectivity toward recognition of 2,4,6-trinitrophenol in wastewater.^20d Further, the modification occurred using different metal ions (a series of [Cu₂(L)] framework) and various organic linkers (H₄L¹ to H₄L¹⁰) for the preparation of NOTT-100 to NOTT-109 series, which are also isostructural metal–organic frameworks.²¹

Text in the Original Manuscript (Section 2.1.3)

Porous Coordination Networks (PCNs)

Porous coordination networks are stereo-octahedron materials, and they have a hole–cage–hole topology with a 3D structure. Some of the PCNs are PCN-333, PCN-224, PCN-222, and PCN-57.¹⁹ One of the PCN MOFs, PCN-222 MOF, is extensively applied in sensors. Ling et al. synthesized a susceptible electrochemical sensor to detect DNA by using PCN-222.²⁶

Revised Text As Follows

Porous Coordination Networks (PCNs)

PCNs, also called MOFs, are a class of nanoporous materials that are formed by connecting metal nodes (metal ions or metallic clusters) with organic and/or inorganic ligands as “linkers”, which allows the creation of 1D, 2D, and 3D networks. Furthermore, PCNs display remarkable properties such as high porosities, large surface areas, tunable pore sizes, and good mechanical and chemical stabilities, exploring them as promising materials in various applications (gas storage, separation, sensing, and catalysis). PCNs exhibit uniform and/or dynamic pore structures due to the presence of a variety of coordination architectures. These materials exhibit highly porous structures with well-defined cavities or channels, providing large surface areas and high porosity. Examples of PCNs include PCN-333, PCN-224, PCN-222, and PCN-57.¹⁹ It was noticed that the PCN-222 MOF is extensively applied in sensors due to its highly tunable structure and the ability to incorporate functional groups. Ling et al. synthesized a susceptible electrochemical sensor to detect DNA by using PCN-222.²⁶

Text in the Original Manuscript (Section 2.1.4)

Materials Institute Lavoisier (MIL) MOFs

Materials Institute Lavoisier MOFs are synthesized using various elements that have valence electrons and an organic compound containing two carboxylic functional groups. The pore size arrangement of MIL MOFs could be converted freely under outward incitement. MIL MOFs contain MIL-101, MIL-100, MIL-53, MIL-88, MIL-125, etc.¹⁹ Zhang and co-workers prepared MIL-101(Cr) through a hydrothermal approach to make resistive humidity sensors with elevated sensitivity.²⁷ MIL composites are used as chemical sensors to immobilize proteins, QDs, and other constituents.^28–30 Importantly, MILs exhibit several unique features such as ultrahigh surface area, uniform pores, and permanent porosity, exploring them as ideal candidates for various applications in biomedical and environmental sciences. Transfer capacity is the structure that prolongs between micropores and mesopores under impassion of the exterior influences.

Revised Text As Follows

Materials Institute Lavoisier (MIL) MOFs

MIL materials are porous metal carboxylate salts composed of different trivalent metal cations and carboxylic acid ligands (dicarboxylates, tricarboxylates) with huge pores and permanent porosity. MIL MOFs such as MIL-101, MIL-100, MIL-53, MIL-88, MIL-127, etc. were used for the photocatalytic applications.^4,19 Zhang and co-workers prepared MIL-101(Cr) through a hydrothermal approach to create resistive humidity sensors with elevated sensitivity.²⁷ Importantly, MIL-101 and NH₂-MIL-88(Fe) MOF hybrids were successfully prepared by mixing with inorganic nanostructures (PtNi, reduced-graphene oxide, and CdSe/ZnS QDs) for electrochemical and fluorescence sensing applications.^28–30 Furthermore, MILs exhibit several unique features such as ultrahigh surface area, uniform pores, and permanent porosity, exploring them as ideal candidates for various applications in biomedical and environmental sciences. Transfer capacity is the structure that prolongs between micropores and mesopores under the impassion of exterior influences.

Text in the Original Manuscript (Section 2.2)

Nomenclature of MOFs

Recently, various constituents which consist of metal ions linked to organic linkers have been reported. These materials are known by various names: metal–organic frameworks, hybrid organic–inorganic materials, metal–organic polymers, coordination polymers, and organic zeolite analogues.³ The word MOF illuminates the presence of an absorbent structure as well as a strong bond responsible for the rigidity of the framework with a distinct geometry where secondary structural units can be replaced throughout the synthesis procedure.⁴³ The MOF abbreviation is generally used as a common name of the class of compound; when it is followed by an ordinal number, it indicates a specific MOF.^44–46

Revised Text As Follows

Nomenclature of MOFs

In recent years, the research interest of MOFs has tremendously increased due to their remarkable applications in multidisciplinary research areas, favoring the design and synthesis of new MOFs. In view of this, the International Union of Pure and Applied Chemistry (IUPAC) has given recommendations and guidelines for the nomenclature and terminology of coordination polymers and MOFs.^43a–c Furthermore, various constituents which consist of metal ions linked to organic linkers have been reported. These materials are known by various names: metal–organic frameworks, hybrid organic–inorganic materials, metal–organic polymers, coordination polymers, and organic zeolite analogues.³ The word MOF illuminates the presence of an absorbent structure as well as a strong bond responsible for the rigidity of the framework with a distinct geometry where secondary structural units can be replaced throughout the synthesis procedure.⁴³ The MOF abbreviation is generally used as a common name of the class of compound; when it is followed by an ordinal number, it indicates a specific MOF.^44–46

Text in the Original Manuscript (Section 3.1, Line 19 (Right side, Pg No.: 44510))

Polar molecules in a substrate mixture attempt to align themselves in an electromagnetic field and in an oscillating field, changing their orientations permanently as a result.

Revised Text As Follows

In microwave synthesis, an oscillator converts high-voltage direct current into high-frequency radiation. Generally, two polarization (dipolar and ionic) mechanisms are observed in microwave frequencies. The dipolar mechanism is due to the permanent dipole of a molecule such as water, favoring reorientation and alignment themselves in the direction of the applied electric field of microwaves, whereas the ionic mechanism occurs due to the displacement of ions (cations and anions) in the solution by the oscillating electric field.

Text in the Original Manuscript (Section 3.2, Line 7 (Right Side, Pg No.: 44511))

The electrochemical method of MOFs uses electrons as a source of metal ions are passed through a reaction mixture, which contains dissolved organic linker molecules and an electrolyte via anodic dissolution as metal source instead of metal salts.

Revised Text As Follows

In the electrochemical synthesis of MOFs, metal ions are consistently sourced through anodic dissolution to serve as the primary metal source. These ions, continually supplied via anodic dissolution, interact with organic linker molecules and electrolytes within the reaction medium, resulting in the formation of MOF crystals.

Text in the Original Manuscript (Section 3.3, Line 25 (Left Side, Pg No.: 44512))

Due to the high pressure, the solvent is heated above its boiling point and the salt will melt, which then aids the reaction. In addition, to acquire a large crystal with a high internal surface area, slow crystallization from a solution is required.

Revised Text As Follows

Under the solvothermal conditions, the solubilities of metal salts and organic ligands are greatly improved which favors the increase of the mobilities of dissolved metal salts and ligands, which then aids the reaction for the growth of materials. Moreover, the slow crystallization process from the solution promotes the formation of large, regular crystals with a high internal surface area.

Text in the Original Manuscript (Section 3.5, Lines 8–11 (Pg No.: 44512))

The main factor for the cavitation’s impact on a liquid is ultrasonic. Cavitation is the name for the development and collapse of bubbles created in a solution after sonication.

Revised Text As Follows

The cavitation and rarefaction cycles are produced by acoustic waves in a liquid medium, causing physical and chemical effects of ultrasound, which favors the growth of materials with unique architectures.

Text in the Original Manuscript (Section 4, Paragraph 2, Line 16 (Left Side, Pg No.: 44515))

Among them, H₂O has the highest attraction toward Mg, whereas other solvent mixtures (EtOH:H₂O and DMF:MeOH) did not coordinate with the metal centers, signifying that the use of water as a solvent greatly influenced formation of covalent bonds with the metal ions.

Revised Text As Follows

Among them, H₂O has high affinity to coordinate with Mg²⁺ ion centers, and DMF exhibited a lower affinity toward Mg²⁺ ion centers as compared to H₂O, whereas MeOH and EtOH showed no affinity toward Mg²⁺ ion centers in the presence of H₂O and DMF, respectively. This result demonstrated that H₂O exhibited high affinity to coordinate with Mg²⁺ ion centers over other polar solvents (EtOH, MeOH, and DMF), which favors the construction of 3D Mg-based MOFs.

Text in the Original Manuscript (Section 4, Paragraph 3, Lines 1–6 (Left Side, Pg No.: 44515)

The temperature is another critical factor which affects the characteristics of the synthesized MOFs. Due to the reactant’s good solubility and the production of large crystals with high superiority, the material exhibits a high crystallization nature at high temperatures. The temperature of the reaction mixture is affected by the nucleation and crystal growth rates.

Revised Text As Follows

The temperature is another critical factor which affects the characteristics of the synthesized MOFs since the solubility of organic ligands and metal salts, tuning of the coordination mode of organic ligands, the reaction rate (kinetics), and reaction thermodynamics are strongly influenced by reaction temperature. Furthermore, the reaction temperature plays a vital role in synthesizing MOFs with multidimensional architectures. The coordination number of metal ions and the dimensionality of MOFs can be increased by increasing the reaction temperature.

We regret the above-mentioned errors in the published paper, which do not materially impact the classification of MOFs, synthetic approaches for MOFs, influencing factors for MOF synthesis, applications of MOFs in Energy, Drug Delivery, and Wastewater Treatment, and conclusions of the paper as published.

References in the Original Manuscript

[2] Sharmin, E.; Zafar, F. Introductory Chapter: metal-organic frameworks (MOFs). Metalorganic frameworks; InTech, 2016; pp 1-16; DOI: 10.5772/64797.

[3] Butova, V. V. E.; Soldatov, M. A.; Guda, A. A.; Lomachenko, K. A.; Lamberti, C. Metalorganic frameworks: structure, properties, methods of synthesis and characterization. Russ. Chem. Rev.2016, 85 (3), 280.

[20] Zhu, M.; Wu, X.; Niu, B.; Gui, H.; Zhang, Y. Fluorescence sensing of 2, 4, 6-trinitrophenol based on hierarchical IRMOF-3 nanosheets fabricated through a simple one-pot reaction. Appl. Organomet. Chem.2018, 32 (5), e4333, 10.1002/aoc.4333.

[21] Abedi, S.; Tehrani, A. A.; Morsali, A. Mechanochemical synthesis of isoreticular metal–organic frameworks and comparative study of their potential for nitrobenzene sensing. New J. Chem. 2015, 39 (7), 5108–5111.

[43] Roswell, J. L.; Yaghi, O. M. Metal–organic frameworks: a new class of porous materials. Microporous Mesoporous Mater.2004, 73 (1–2), 3–14.

Revised and Added References

Revised references 2 and 3.

[2] Jiang, H. L.; Makal, T. A.; Zhou, H. C. Interpenetration control in metal–organic frameworks for functional applications. Coord. Chem. Rev.2013, 257, 2232–2249. 10.1016/j.ccr.2013.03.017.

[3] Furukawa, S.; Reboul, J.; Diring, S.; Sumida, K.; Kitagawa, S. Structuring of metal–organic frameworks at the mesoscopic/macroscopic scale. Chem. Soc. Rev.2014, 43, 5700–5734. 10.1039/C4CS00106K.

Added references.

[3a] Janiak, C.; Vieth, J. K. MOFs, MILs and more: concepts, properties and applications for porous coordination networks (PCNs). New J. Chem.2010, 34, 2366–2388. 10.1039/C0NJ00275E.

[3b] Liu, X.; Zhou, Y.; Zhang, J.; Tang, L.; Luo, L.; Zeng, G. Iron Containing Metal–Organic Frameworks: Structure, Synthesis, and Applications in Environmental Remediation. ACS Appl. Mater. Interfaces2017, 9 (24), 20255–20275. 10.1021/acsami.7b02563.

[3c] Natarajan, S.; Mahata, P. Metal–organic framework structures – how closely are they related to classical inorganic structures. Chem. Soc. Rev.2009, 38, 2304–2318. 10.1039/B815106G.

Revised and added references.

[20] Eddaoudi, M. K.; Jaheon, R. N.; Vodak, D.; Wachter, J. O. K.; Yaghi, O. M. Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage. Science2002, 295, 469.

[20a] Mai, Z.; Liu, D. Synthesis and Applications of Isoreticular Metal–Organic Frameworks IRMOFs-n (n = 1, 3, 6, 8). Cryst. Growth Des.2019, 19, 7439–7462.

[20b] Doonan, C. J.; Morris, W.; Furukawa, H.; Yaghi, O. M. Isoreticular Metalation of Metal-Organic Frameworks. J. Am. Chem. Soc.2009, 131, 9492–9493.

[20c] Fan, W.; Zhang, X.; Kang, Z.; Liu, X.; Sun, D. Isoreticular chemistry within metal–organic frameworks for gas storage and separation. Coord. Chem. Rev.2021, 443, 213968.

[20d] Zhu, M.; Wu, X.; Niu, B.; Guo, H.; Zhang, Y. Fluorescence sensing of 2, 4, 6-trinitrophenol based on hierarchical IRMOF-3 nanosheets fabricated through a simple one-pot reaction. Appl. Organomet. Chem.2018, 32 (5), e4333. 10.1002/aoc.4333.

[21] Lin, X.; Telepeni, I.; Blake, A. J.; Dailly, A.; Brown, C. M.; Simmons, J. M.; Zoppi, M.; Walker, G. S.; Thomas, K. M.; Mays, T. J.; Hubberstey, P. High-capacity hydrogen adsorption in Cu (II) tetracarboxylate framework materials: the role of pore size, ligand functionalization, and exposed metal sites. J. Am. Chem. Soc.2009, 131 (6), 2159–2171.

[43a] Rowselll, J.; Yaghi, O. M. Metal–organic frameworks: a new class of porous materials. Microporous Mesoporous Mater.2004, 73 (1-2), 3–14.

[43b] Batten, S. R.; Champness, N. R.; Chen, X.-M.; Kitagawa, S.; Öhrström, L.; O’Keeffe, M.; Paik Suh, M.; Reedijk, J. Terminology of metal–organic frameworks and coordination polymers (IUPAC Recommendations 2013). Pure and Applied Chemistry2013, 85 (8), 1715–1724.

[43c] Batten, S. R.; Champness, N. R.; Chen, X.-M.; Garcia-Martinez, J.; Kitagawa, S.; Öhrström, L.; O’Keeffe, M.; Reedijkij, J. Coordination polymers, metal–organic, frameworks and the need for terminology guidelines. CrystEngComm2012, 14, 3001–3004.