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Gas storage and separation are closely associated with the alleviation of greenhouse effect, the widespread use of clean energy, the control of toxic gases, and various other aspects ...in human society. In this review, we highlight the recent advances in gas storage and separation using metal-organic frameworks (MOFs). In addition to summarizing the gas uptakes of some benchmark MOFs, we emphasize on the desired chemical properties of MOFs for different gas storage/separation scenarios. Greenhouse gases (CO2), energy-related gases (H2 and CH4), and toxic gases (CO and NH3) are covered in the review.
Metal–organic frameworks (MOFs) are an emerging class of porous materials with potential applications in gas storage, separations, catalysis, and chemical sensing. Despite numerous advantages, ...applications of many MOFs are ultimately limited by their stability under harsh conditions. Herein, the recent advances in the field of stable MOFs, covering the fundamental mechanisms of MOF stability, design, and synthesis of stable MOF architectures, and their latest applications are reviewed. First, key factors that affect MOF stability under certain chemical environments are introduced to guide the design of robust structures. This is followed by a short review of synthetic strategies of stable MOFs including modulated synthesis and postsynthetic modifications. Based on the fundamentals of MOF stability, stable MOFs are classified into two categories: high‐valency metal–carboxylate frameworks and low‐valency metal–azolate frameworks. Along this line, some representative stable MOFs are introduced, their structures are described, and their properties are briefly discussed. The expanded applications of stable MOFs in Lewis/Brønsted acid catalysis, redox catalysis, photocatalysis, electrocatalysis, gas storage, and sensing are highlighted. Overall, this review is expected to guide the design of stable MOFs by providing insights into existing structures, which could lead to the discovery and development of more advanced functional materials.
Stable metal–organic frameworks (MOFs) with high resistance to harsh chemical environments are reviewed with regard to recent progress in their research and development. Fundamental mechanisms of MOF stability, the design and synthesis of stable MOF architectures, and their latest applications are summarized, providing a fundamental outline for the discovery of new stable MOFs.
The recombination of electron–hole pairs severely detracts from the efficiency of photocatalysts. This issue could be addressed in metal–organic frameworks (MOFs) through optimization of the ...charge-transfer kinetics via rational design of structures at atomic level. Herein, a pyrazolyl porphyrinic Ni-MOF (PCN-601), integrating light harvesters, active catalytic sites, and high surface areas, has been demonstrated as a superior and durable photocatalyst for visible-light-driven overall CO2 reduction with H2O vapor at room temperature. Kinetic studies reveal that the robust coordination spheres of pyrazolyl groups and Ni-oxo clusters endow PCN-601 with proper energy band alignment and ultrafast ligand-to-node electron transfer. Consequently, the CO2-to-CH4 production rate of PCN-601 far exceeds those of the analogous MOFs based on carboxylate porphyrin and the classic Pt/CdS photocatalyst by more than 3- and 20-fold, respectively. The reaction avoids the use of hole scavengers and proceeds in a gaseous phase which can take full advantage of the high gas uptake of MOFs. This work demonstrates that the rational design of coordination spheres in MOF structures not only reconciles the contradiction between reactivity and stability but also greatly promotes the interfacial charge transfer to achieve optimized kinetics, providing guidance for the design of highly efficient MOF photocatalysts.
A base-resistant porphyrin metal–organic framework (MOF), namely PCN-602 has been constructed with 12-connected Ni8(OH)4(H2O)2Pz12 (Pz = pyrazolate) cluster and a newly designed pyrazolate-based ...porphyrin ligand, 5,10,15,20-tetrakis(4-(pyrazolate-4-yl)phenyl)porphyrin under the guidance of the reticular synthesis strategy. Besides its robustness in hydroxide solution, PCN-602 also shows excellent stability in aqueous solutions of F–, CO3 2–, and PO4 3– ions. Interestingly, the Mn3+-porphyrinic PCN-602, as a recyclable MOF catalyst, presents high catalytic activity for the C–H bond halogenation reaction in a basic system, significantly outperforming its homogeneous counterpart. For the first time, a porphyrinic MOF was thus used as an efficient catalyst in a basic solution with coordinating anions, to the best of our knowledge.
Enzymatic catalytic processes possess great potential in chemical manufacturing, including pharmaceuticals, fuel production and food processing. However, the engineering of enzymes is severely ...hampered due to their low operational stability and difficulty of reuse. Here, we develop a series of stable metal-organic frameworks with rationally designed ultra-large mesoporous cages as single-molecule traps (SMTs) for enzyme encapsulation. With a high concentration of mesoporous cages as SMTs, PCN-333(Al) encapsulates three enzymes with record-high loadings and recyclability. Immobilized enzymes that most likely undergo single-enzyme encapsulation (SEE) show smaller Km than free enzymes while maintaining comparable catalytic efficiency. Under harsh conditions, the enzyme in SEE exhibits better performance than free enzyme, showing the effectiveness of SEE in preventing enzyme aggregation or denaturation. With extraordinarily large pore size and excellent chemical stability, PCN-333 may be of interest not only for enzyme encapsulation, but also for entrapment of other nanoscaled functional moieties.
Despite numerous inherent merits of metal–organic frameworks (MOFs), structural fragility has imposed great restrictions on their wider involvement in many applications, such as in catalysis. Herein, ...a strategy for enhancing stability and enabling functionality in a labile Zr(IV)‐MOF has been proposed by in situ porphyrin substitution. A size‐ and geometry‐matched robust linear porphyrin ligand 4,4′‐(porphyrin‐5,15‐diyl)dibenzolate (DCPP2−) is selected to replace the 4,4′‐(1,3,6,8‐tetraoxobenzolmn3,8phenanthroline‐2,7(1H,3H,6H,8H)‐diyl)dibenzoate (NDIDB2−) ligand in the synthesis of BUT‐109(Zr), affording BUT‐110 with varied porphyrin contents. Compared to BUT‐109(Zr), the chemical stability of BUT‐110 series is greatly improved. Metalloporphyrin incorporation endows BUT‐110 MOFs with high catalytic activity in the photoreduction of CO2, in the absence of photosensitizers. By tuning the metal species and porphyrin contents in BUT‐110, the resulting BUT‐110‐50%‐Co is demonstrated to be a good photocatalyst for selective CO2‐to‐CO reduction, via balancing the chemical stability, photocatalytic efficiency, and synthetic cost. This work highlights the advantages of in situ ligand substitution for MOF modification, by which uniform distribution and high content of the incoming ligand are accessible in the resulting MOFs. More importantly, it provides a promising approach to convert unstable MOFs, which mainly constitute the vast MOF database but have always been neglected, into robust functional materials.
The in situ porphyrin substitution strategy is developed for modifying labile interpenetrated BUT‐109(Zr), affording BUT‐110 with enhanced chemical stability and photocatalytic activity. By tuning the species and contents of metalloporphyrin in BUT‐110, some of the BUT‐110 MOFs may serve as potential photocatalysts for selective CO2‐to‐CO reduction, in the absence of photosensitizer.
A reaction between a ZrIV salt and a porphyrinic tetracarboxylic acid leads to a metal–organic framework (MOF) with two types of open channels, representing a MOF featuring a (4,8)-connected sqc net. ...The MOF remains intact in both boiling water and aqueous solutions with pH ranging from 1 to 11, a remarkably extensive pH range that a MOF can sustain. Given its exceptional stability and pH-dependent fluorescent intensity, the MOF can potentially be applied in fluorescent pH sensing.
A series of mesoporous metalloporphyrin Fe-MOFs, namely PCN-600(M) (M = Mn, Fe, Co, Ni, Cu), have been synthesized using the preassembled Fe3O(OOCCH3)6 building block. PCN-600 exhibits a ...one-dimensional channel as large as 3.1 nm and the highest experimental pore volume of 1.80 cm3g–1 among all the reported porphyrinic MOFs. It also shows very high stability in aqueous solutions with pH values ranging from 2–11 and is to our knowledge the only mesoporous porphyrinic MOF stable under basic aqueous conditions. PCN-600(Fe) has been demonstrated as an effective peroxidase mimic to catalyze the co-oxidation reaction.
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