Cuboctahedral [In₃₆(μ-OH)₂₄(NO₃)₈(Imtb)₂₄]MOF with Atypical Pyramidal Nitrate Ion in SBU: Lewis Acid–Base Assisted Catalysis and Nanomolar Sensing of Picric Acid

Abstract

A robust and multifunctional cuboctahedral [In 36 (μ-OH) 24 (NO 3 ) 8 (Imtb) 24 ] MOF (In(Imtb)-MOF) with an atypical pyramidal nitrate ion-containing hitherto unknown SBU core [In 9 (μ-OH) 6 (NO 3 )] is reported. The intra-and interlayer nitrate ions adopt pyramidal and inverted pyramidal shapes, which separates the active indium site [(In 3 (μ-OH) 2 )NO 3 -(In 3 (μ-OH) 2 )] and linear In 3 (μ-OH) 2 by 0.5 and 0.9 nm, respectively. Additionally, the high density of active metal sites shows remarkable catalytic activity with higher TOF even for sterically hindered substrates in Strecker synthesis and CO 2 cycloaddition. Moreover, the luminescence behavior of In(Imtb)-MOF and the presence of uncoordinated nitrogen atoms are exploited for selective sensing of explosive trinitrophenol (TNP) with a detection limit (LOD) of 2.3 ppb.

Multifunctional lanthanide MOF luminescent sensor built by structural designing and energy level regulation of a ligand

“…The hydrogen bonding interactions are: N–H⋯O d = 2.744 Å, θ = 149.94°; N–H⋯O d = 3.047 Å, θ = 159.64°; N–H⋯O d = 2.976 Å, θ = 175.65°; N–H⋯O d = 2.764 Å, θ = 153.81°. As reported in the literature, 48 these hydrogen bonding interactions are moderate. And the π–π stacking interactions between naphthalene groups belong to a parallel displaced conformation.…”

“…Picric acid (PA) is one of the most dangerous nitro explosives, so it is necessary to detect PA selectively and quickly. [46][47][48][49] As PA has three nitro groups and one hydroxyl group, it is inferred that the Eu-MOF might recognize PA by hydrogen bonding interactions. This assumption was verified by the following experiment.…”

Nanochannel {InZn}–Organic Framework with a High Catalytic Performance on CO2 Chemical Fixation and Deacetalization–Knoevenagel Condensation

“…The design and synthesis of porous metal–organic frameworks (MOFs) have aroused great attention because of their promising application in a series of regions, such as polytypic catalysis, fluorescence sensing, drug delivery, gas separation/storage, magnetism, optoelectronics, and so on. − Since the first report of MOF-catalyzed cycloaddition by Han et al, there have been a lot of studies on CO 2 cycloaddition catalyzed by various MOFs, which are differentiated by their constituents and connectivities. − In terms of documented references, indium-based organic frameworks (In-OFs) have become a basically reliable heterogeneous catalyst because of the unique traits of In 3+ ion including accessible high-level p orbitals, diverse coordination numbers, and distinctive electronic configurations, which render them the ability to serve as facile Lewis acid sites to activate the involved reactants of CO 2 and epoxides during the chemical conversion of epoxides to cyclocarbonates. − Moreover, in the past few years, zinc-based MOFs (Zn-MOFs) with well-ordered structures or networks are also well developed for a confirmed high catalytic performance on the chemical fixation of CO 2 under mild solvent-free conditions because of their moderate Lewis acidity and affinity to CO 2 and epoxide molecules from 3d 10 zinc cations. − In 2013, Williams et al first reported that heterodinuclear MOF catalysts exhibited evidently higher activity upon the cycloaddition or copolymerization of CO 2 and epoxide than the homodinuclear ones, which might be due to the fact that the combination of chemically dissimilar metals displayed discrepant bimetallic surfaces and a high concentration of regularly distributed Lewis acid sites. − So far, although the coexisting secondary building units (SBUs) of {InM 2 }, {In 2 M 2 }, {In 3 Ln}, and {In 3 Ln 2 } are reported, , the oriented strategy of integrating In 3+ 5p and Zn 2+ 3d metal elements into one SBU as inorganic nodes in MOFs has not yet been explored, maybe because the high and multifarious coordination numbers of In 3+ and Zn 2+ ions facially lead to their incompatibility.…”

Catalytic Investigation of CO2 Chemical Fixation and the Knoevenagel Condensation Reaction for a TmIII–Organic Framework

“…10,11 Furthermore, recent scientific studies have confirmed the collaborative environment of activated transition metals (Lewis acid sites) and nucleophilic groups (Lewis base sites) in porous MOFs, which could improve the catalytic efficiency of chemical immobilization of CO 2 by the condensation reaction of epoxy compounds and Knoevenagel. 12,13 However, the further development is greatly limited by the fact that most documented MOFs tend to have poor chemical or thermal stability. 14 Moreover, among all porous MOFs, Ln-MOFs are the most efficient heterogeneous catalyst with the longest duration, due to the abundant vacant electron orbitals of Ln 3+ cations and a strong affinity for CO 2 molecules with large dipole moments.…”

“…Porous metal–organic frameworks (MOFs), obtained from the self-assembly of metal cations and specific ligands, have aroused great interest because of their excellent physicochemical characteristics including high porosity and specific surface area, well-distributed channels, and abundant Lewis acid–base sites, which give them a wide range of potential applications in gas selective separation and storage, catalysis, fluorescence recognition, and other fields. − Over the past few decades, various methods have been used to improve the aboriginal performance of MOFs. It was considered to be the most effective functionalization strategy by introducing the mixed functional ligands with special functional groups into the MOF framework. , Until now, a large amount of functionalized MOFs have been obtained by simple chemical condensation or Suzuki coupling reactions with nitrogen-containing heterocyclic organic ligands such as pyridine and imidazole, which are derived from halogenated hydrocarbons, phenylboric acid derivatives, imidazoles, and triazoles. , Furthermore, recent scientific studies have confirmed the collaborative environment of activated transition metals (Lewis acid sites) and nucleophilic groups (Lewis base sites) in porous MOFs, which could improve the catalytic efficiency of chemical immobilization of CO 2 by the condensation reaction of epoxy compounds and Knoevenagel. , However, the further development is greatly limited by the fact that most documented MOFs tend to have poor chemical or thermal stability . Moreover, among all porous MOFs, Ln-MOFs are the most efficient heterogeneous catalyst with the longest duration, due to the abundant vacant electron orbitals of Ln 3+ cations and a strong affinity for CO 2 molecules with large dipole moments .…”