Strategies for induced defects in metal–organic frameworks for enhancing adsorption and catalytic performance

Abstract

Metal-organic frameworks (MOFs) have emerged among porous materials. The designable structure and specific functionality make them stand out for diverse applications. In conceptual MOF, the metal ions/clusters and organic ligands...

Metal–Organic Frameworks for CO2 Separation from Flue and Biogas Mixtures

“…The defects in MOFs are defined as "sites that locally break the regular periodic arrangement of atoms or ions of the static crystalline parent framework because of missing or dislocated atoms or ions". [502] Defects in MOFs' structure have a significant impact on tuning their functional properties, which further enhance the performance in various applications, as pioneered by several groups. [503][504][505] MOFs' defect formation could be categorized into two types: (a) missing linkers which could also be termed as "metal defect" and (b) missing metal also termed as "ligand defect".…”

“…[503][504][505] MOFs' defect formation could be categorized into two types: (a) missing linkers which could also be termed as "metal defect" and (b) missing metal also termed as "ligand defect". [502] Although defects are the inherent property of MOFs, they could also be created intentionally by employing several synthesis strategies such as mixed ligand synthesis, use of modulators, postsynthetic modification, and so on. [505] As metal ions and linkers act as the active sites of developed MOFs, their defects tune the structural properties and influence their applications.…”

“…However, to improve the CO 2 capture by defective MOFs, several strategies were adopted such as (a) coordinatively unsaturated metal site introduction, (b) H-bonding residues incorporation, and (c) basic site functionalization. [502] Additionally, partial removal of organic linkers can also enhance the porosity of the MOFs and lead to open access to the previously inaccessible regions, which further create new interaction sites and improve the sorption capacity. In recent work, Navarro et al nicely displayed how strategically developed defective MOF can exhibit improved CO 2 capture from flue gas mixture.…”

Titanium–Porphyrin Metal–Organic Frameworks as Visible-Light-Driven Catalysts for Highly Efficient Sonophotocatalytic Reduction of Cr(VI)

“…Metal–organic frameworks (MOFs), integrated with metal clusters/ions and organic linkers through coordination bonds, are well known as a kind of functional hybrid materials. − Through appropriately selecting these inorganic or organic building blocks, the photophysical process of MOFs could be effectively regulated and controlled at the molecular level, which promoted the preparation and application of MOF photocatalysts. − Compared with some 1D or 2D semiconductor photocatalysts, MOFs possess the superiority of easily functionalized pore structures, high density of catalytic sites, and large specific surface area, which is convenient for adsorption and conversion of Cr­(VI) . In recent years, numerous MOFs were designed through combining photoactive ligands (e.g., organometallic complexes and porphyrin derivatives) and high valence metallic ions (e.g., Zr 4+ , Fe 3+ , and Ti 4+ ), where this kind of MOF possesses visible-light harvesting, robust nature, and various types of catalytic active sites, exhibiting notable performance in the photocatalytic Cr­(VI) reduction system. − Although the open frameworks endow MOFs with a large specific surface area, the long range-ordered pore structure also hampers the photogenerated charge transfer in the structures, limits the substrate or product mass transfer in the channel of MOFs, and ultimately affects the catalytic efficiency of reactions. , Hence, a new MOF-based photocatalytic Cr­(VI) reduction system should be developed to improve the abovementioned issues.…”

Ligand functionalization of defect-engineered Ni-MOF-74

“…The defect engineering of metal-organic frameworks (MOFs) has received increasing interest because MOFs with certain structural defects can outperform defect-free MOFs in many applications. [1][2][3][4] Among several reported defect generation methods, fragmented ligand installation has been conrmed to be a simple and efficient synthetic strategy to induce defects in MOF structures, where the fragment exhibits lower connectivity than the pristine ligand. [5][6][7] In general, fragmented ligand installation employs a mixed-ligand synthesis approach 8 that can efficiently introduce various functionalities into MOFs while retaining the parent MOF structure.…”