Catalysis through Dynamic Spacer Installation of Multivariate Functionalities in Metal–Organic Frameworks

Topology-Based Functionalization of Robust Chiral Zr-Based Metal-Organic Frameworks for Catalytic Enantioselective Hydrogenation

The design and development of robust and porous supported catalysts with high activity and selectivity is extremely significant but very challenging for eco-friendly synthesis of fine chemicals and pharmaceuticals. We report here the design and synthesis of highly stable chiral Zr(IV)-based MOFs with different topologies to support Ir complexes and demonstrate their network structures-dependent asymmetric catalytic performance. Guided by the modulated synthesis and isoreticular expansion strategy, five chiral Zr-MOFs with a flu or ith topology are constructed from enantiopure 1,1'-biphenol-derived tetracarboxylate linkers and Zr₆, Zr₉, or Zr₁₂ clusters. The obtained MOFs all show high chemical stability in boiling water, strongly acidic, and weakly basic aqueous solutions. The two flu MOFs featuring the dihydroxyl groups of biphenol in open and large cages, after sequential postsynthetic modification with P(NMe₂)₃ and [Ir(COD)Cl]₂, can be highly efficient and recyclable heterogeneous catalysts for hydrogenation of α-dehydroamino acid esters with up to 98% ee, whereas the three ith MOFs featuring the dihydroxyl groups in small cages cannot be installed with P(NMe₂)₃ to support the Ir complex. Incorporation of Ir-phosphorus catalysts into Zr-MOFs leads to great enhancement of their chemical stability, durability, and even stereoselectivity. This work therefore not only advances Zr-MOFs as stable supports for labile metal catalysts for heterogeneous asymmetric catalysis but also provides a new insight into how highly active chiral centers can result due to the framework topology.

Synthesis of Metal-Organic Frameworks MIL-101(Cr)-NH2 Containing Phosphorous Acid Functional Groups: Application for the Synthesis of N-Amino-2-pyridone and Pyrano [2,3-c]pyrazole Derivatives via a Cooperative Vinylogous Anomeric-Based Oxidation

In the current paper, we successfully developed and used metal-organic frameworks (MOFs) based on MIL-101(Cr)-NH2 with phosphorus acid functional groups MIL-101(Cr)-N(CH2PO3H2)2. The synthesized metal-organic frameworks (MOFs) as a multi-functional heterogeneous and nanoporous catalyst were used for the synthesis of N-amino-2-pyridone and pyrano [2,3-c]pyrazole derivatives via reaction of ethyl cyanoacetate or ethyl acetoacetate, hydrazine hydrate, malononitrile, and various aldehydes. The final step of the reaction mechanism was preceded by a cooperative vinylogous anomeric-based oxidation. Recycle and reusability of the described catalyst MIL-101(Cr)-N(CH2PO3H2)2 were also investigated.

Tubular metal organic frameworks from the curvature of 2D-honeycombed metal coordination

A tubular MOF with adequate active sites is prepared by the bending of metal-coordinated honeycombed frameworks via titration and shows fast catalytic kinetics with lower catalytic loading for CO2 conversion. The TON is observed to be 2300 and the corresponding TOF of up to 173 h-1 is achieved for the first time.

The effect of coordinated solvent molecules on metal coordination environments in single-crystal-to-single-crystal transformations

We summarized the effect of coordinated solvent molecules on the metal coordination environments in single-crystal to single-crystal transformations.

New two-dimensional Cd(ii) coordination networks bearing benzimidazolyl-based linkers as bifunctional chemosensors for the detection of acetylacetone and Fe3+

Two new CPs, namely {[Cd(L)(1,4-PDA)]·0.7(C₂H₅OH)}_n (1) and {[Cd(L)_0.5(1,8-NDC)·H₂O]}_n (2) were fabricated. 1 shows a sql 2D network. 2 shows a 2D 3,4L83 network. Both 1 and 2 were highly selective and sensitive fluorescent chemosensors toward acetylacetone and Fe³⁺.

An N,N'-diethylformamide solvent-induced conversion cascade within a metal-organic framework single crystal

Crystals of a two-dimensional (2D) metal-organic framework (MOF) [Cd3(BTB)2(DEF)4]·2(DEF)0.5 (1; BTB = benzene-1,3,5-tribenzolate; DEF = N,N'-diethylformamide) immersed in a solution of trans-1,2-bis(4-pyridyl)ethylene (BPEE) yields an interpenetrated three-dimensional (3D) MOF of [Cd3(BTB)2(BPEE)(H2O)2]·(BPEE)·xSol (2). Crystals of MOF 2, in turn, undergo a cascade conversion when immersed in DEF, yielding [Cd3(BTB)2(BPEE)1.8(DEF)0.9(H2O)0.8]·xSol (3a) over 100 seconds and [Cd3(BTB)2(BPEE)2(DEF)2]·xSol (4) after one hour, before finally shuttling back to MOF 1 after six hours.

Metal–organic frameworks as acid- and/or base-functionalized catalysts for tandem reactions

In this article, we have reviewed the development of MOFs anchored with acidic and/or basic sites as heterogeneous catalysts for tandem/cascade (domino) reactions over the past five years.

Highly Stable Copper(I)-Thiacalix[4]arene-Based Frameworks for Highly Efficient Catalysis of Click Reactions in Water

Environmentally friendly metal-organic frameworks (MOFs) have gained considerable attention for their potential use as heterogeneous catalysts. Herein, two Cu^I -based MOFs, namely, [Cu₄ Cl₄ L]⋅CH₃ OH⋅1.5 H₂ O (1-Cl) and [Cu₄ Br₄ L]⋅DMF⋅0.5 H₂ O (1-Br), were assembled with new functionalized thiacalix[4]arenes (L) and halogen anions X^- (X=Cl and Br) under solvothermal conditions. Remarkably, catalysts 1-Cl and 1-Br exhibit great stability in aqueous solutions over a wide pH range. Significantly, MOFs 1-Cl and 1-Br, as recycled heterogeneous catalysts, are capable of highly efficient catalysis for click reactions in water. The MOF structures, especially the exposed active Cu^I sites and 1D channels, play a key role in the improved catalytic activities. In particular, their catalytic activities in water are greatly superior to those in organic solvents or even in mixed solvents. This work proposes an attractive route for the design and self-assembly of environmentally friendly MOFs with high catalytic activity and reusability in water.

Well-distributed Pt-nanoparticles within confined coordination interspaces of self-sensitized porphyrin metal-organic frameworks: synergistic effect boosting highly efficient photocatalytic hydrogen evolution reaction

Effective conversion of solar energy into chemical energy by visible light represents a potential strategy for sustainable development. Among which, photocatalytic hydrogen evolution reaction (HER) with a relatively small activation energy (1.23 eV, around 1000 nm light irradiation) is especially attractive. In this work, well-distributed platinum nanoparticles (Pt-NPs) with a width of about 3 nm have been successfully immobilized into the confined coordination interspaces of 3.7 nm diameter, which are facilitated by early transition metal Hf(iv)-based clusters of a self-sensitized palladium porphyrin metal-organic framework. Under visible light irradiation, the resultant Pt@Pd-PCN-222(Hf) (which is also denoted as Pt@Pd-PMOF-2(Hf)) displays superb photocatalytic activity, achieving an unprecedented maximum H2 evolution rate of 22 674 μmol g-1 h-1 with a turn-over number (TON) of 4131.2 in 32 h and the highest turn-over frequency (TOF) of 482.5 h-1 based on Pt-NPs. This photocatalyst can be recycled and reused for three successive runs without significant loss of catalytic activity. This effective strategy takes advantage of the synergetic effect between Pd-porphyrin photosensitizers and Pt-NP co-catalysts confined within nanoscale coordination interspaces incorporating hydrophilic Hf(iv)-oxo clusters.

Exploiting Microwave Chemistry for Activation of Metal-Organic Frameworks

Microwave is thought of as a useful electromagnetic radiation tool because it is often used in real life as well as in a variety of chemical processes. Meanwhile, activation of metal-organic frameworks (MOFs), which must be essentially done to remove coordinating and pore-filling solvents before the use of MOFs for various applications, has been performed commonly with the methods of heat supply or solvent exchange. Here, we show a new methodological microwave activation (MA), realizing it with various MOFs such as HKUST-1, UiO-66, and MOF-74s. For instance, microwave irradiation to the MOF samples for 4-35 min leads to the complete activation of the MOFs without structural damage. As described below, we further demonstrate that the solvent-assisted MA, which is the MA process performed after the solvent exchange, can substantially reduce the time for the activation by 4 min.

In situ growth of ZIF-8-derived ternary ZnO/ZnCo2O4/NiO for high performance asymmetric supercapacitors

In this paper, the rational design and synthesis of ZIF-8-derived ternary ZnO/ZnCo₂O₄/NiO wrapped by nanosheets is introduced. Polyhedral ternary ZnO/ZnCo₂O₄/NiO composites surrounded by nanosheets with different compositions are successfully fabricated through in situ growth on ZIF-8 templates and subsequent thermal annealing in air. Electrochemical investigation reveals that when the molar ratio of nickel nitrate to cobalt nitrate is 1, the composite material is more outstanding, which shows a high specific capacitance of 1136.4 F g^-1 at 1 A g^-1 and excellent cycling stability of 86.54% after 5000 cycles. Moreover, the excellent performance of this material is also confirmed by assembling an asymmetric supercapacitor. The assembled hybrid device can reach a large potential range of 0-1.6 V and deliver a high energy density of 46.04 W h kg^-1 as well as the maximum power density of 7987.5 W kg^-1.

Highly Stable Zr(IV)-Based Metal-Organic Frameworks with Chiral Phosphoric Acids for Catalytic Asymmetric Tandem Reactions

Heterogeneous Brønsted acid catalysts featuring high porosity, crystallinity, and stability have been of great interest for both fundamental studies and practical applications, but synthetically, they still face a formidable challenge. Here, we illustrated a ligand design strategy for directly installing chiral phosphoric acid catalysts into highly stable Zr-MOFs by sterically protecting them from coordinating with metal ions. A pair of chiral porous Zr(IV)-MOFs with the framework formula [Zr₆O₄(OH)₈(H₂O)₄(L)₂] were prepared from enantiopure 4,4',6,6'-tetra(benzoate) and -tetra(2-naphthoate) ligands of 1,1'-spirobiindane-7,7'-phosphoric acid. They share the same topological structure but differ in channel sizes, and both of them demonstrate excellent tolerance toward water, acid and base. Significantly enhanced Brønsted acidity was observed for the phosphoric acids that are uniformly distributed within the frameworks in comparison with the nonimmobilized acids. This not only facilitates the catalysis of asymmetric two-component tandem acetalization, Friedel-Crafts, and iso-Pictet-Spengler reactions but also promotes the catalysis of asymmetric three-component tandem deacetalization-acetalization and Friedel-Crafts reactions benefiting from the synergy with exposed Lewis acidic Zr(IV) sites. The enantioselectivities are comparable or favorable compared to those obtained from the corresponding homogeneous systems. The features of high reactivity, selectivity, stability, and recyclability for Zr(IV)-MOFs make them hold promise as a new type of heterogeneous acid catalyst for the eco-friendly synthesis of fine chemicals.

Eight coordination compounds assembled from unexplored semi-rigid ether-based unsymmetrical tetracarboxylate and various dipyridyl ligands: structural variation, magnetic and photoluminescence properties

Eight new coordination compounds built by an unexplored semi-rigid ether-based unsymmetrical tetracarboxylate and varied dipyridyl ligands have been synthesized. Their variety of structures, photoluminescence and magnetic properties are discussed.

Antigen-enabled facile preparation of MOF nanovaccine to activate the complement system for enhanced antigen-mediated immune response

Since current subunit vaccines are limited by a short halflife in vivo and weak immune responses when used alone without adjuvants, there is an unmet need for combing carriers with complement activation signals to interrupt outbreaks in real-time.

New linker installation in metal–organic frameworks

Installation of new organic components (including multitopic anionic and neutral linkers) in MOFs and MOPs for multicomponent materials.