Bifunctional metal–organic frameworks afforded by postsynthetic modification for efficient cycloaddition of CO₂ and epoxides

Abstract

Bifunctional ionic metal-organic frameworks (MOFs) containing Lewis acid sites (unsaturated metal sites) and halide ions (Cl À , Br À , and I À ) have attracted increasing attention due to their extra high activity for the cycloaddition of CO 2 with epoxides. Herein, a novel microporous MOF (1-Eu), namely,dine-4-yl)pyridine), has been synthesized by using a new bipyridyl-based tetracarboxylate ligands (H 4 L). Structural analyses show that 1-Eu is a 3D framework in which 1D chains with alternating triple and single carboxylate bridges are interlinked by the L ligands and contains microporous channels with uncoordinated pyridyl N atoms, which are easy to be modified by Nmethylation. Therefore, three bifunctional N-methylation 1-Eu MOFs, 1-Eu-MeX (X = Cl À , Br À , and I À ), were successfully prepared from the 1-Eu MOF by a postsynthetic modification (PSM) method. 1-Eu-MeX can efficiently cata-

Mesoporous MOF Based on a Hexagonal Bipyramid Co8-Cluster: High Catalytic Efficiency on the Cycloaddition Reaction of CO2 with Bulky Epoxides

“…Since the product of 2-[(1-Naphthyloxy) methyl] oxirane can solidify during the reaction and that affects the reaction efficiency, we have performed the catalytic reaction in 2 mL of acetonitrile. In contrast to some MOF-based materials which only show high catalysis to small substrates, − LCU-606 has better catalytic activity towards bulky epoxide substrates due to its large channel size.…”

“…Cyclic carbonates are widely used in pharmaceuticals, dye, electrolyte in the lithium-ion batteries, intermediates for the synthesis of ethylene glycol, polymeric materials, precursor of polycarbonates, etc. − Therefore, the synthesis of cyclic carbonates via the cycloaddition of CO 2 into epoxides is a primary target for industrial applications. A wide variety of catalysts have been developed for the CO 2 cycloaddition reaction, including metal-Schiff bases, zeolites, ionic liquids-supported solids, salen complexes, and metal–organic frameworks (MOFs). − Among these catalysts, MOFs have shown promising application prospects in thermal catalytic conversion of CO 2 owing to high porosity and abundant active sites. − However, reported MOF-based catalysts have also some shortcomings, such as poor stability of the framework and the limitation of narrow pore apertures on the substrate transfer in the reaction, especially for those with large molecule sizes. For example, we have reported a titanium-based MOF, LCU-402, with pore apertures of 4.9 × 6.5 Å.…”

Cage-Space-Partitioned Metal–Organic Frameworks for Efficient Carbon Dioxide Capture and Conversion

“…In general, no matter whether SNNU-337 or SNNU-338, the same catalytic system has different catalytic effects on different substrates. With the increase of substrate substituents, the steric effect also gradually increases, which makes it difficult for them to bind to the site of action, resulting in a gradual decrease in yield . However, it is worth noting that for the same substrate, the catalytic effect of SNNU-338 is higher than that of SNNU-337 (Figure ), further partition leads to the full contact between the substrate and MOFs, and the synergistic effect between the partition and OMSs visibly enhances the catalytic effect of MOFs on the substrate.…”

“…With the increase of substrate substituents, the steric effect also gradually increases, which makes it difficult for them to bind to the site of action, resulting in a gradual decrease in yield. 42 However, it is worth noting that for the same substrate, the catalytic effect of SNNU-338 is higher than that of SNNU-337 (Figure 5), further partition leads to the full contact between the substrate and MOFs, and the synergistic effect between the partition and OMSs visibly enhances the catalytic effect of MOFs on the substrate. In all, the synergistic effects of CSP in large M 60 -cages and OMSs in M 12 -cages make SNNU-337/338 MOFs excellent catalysts to catalyze CO 2 cycloaddition with various epoxides.…”

The post-synthesis modification (PSM) of MOFs for catalysis

“…There are far fewer examples of MOF catalysts that have been generated via the PSM of non-amine reactive handles such as nitrogen heterocycles, 6,23–26 aldehydes, 27–29 acid anhydrides, etc . 30 The advantage of non-amine reactive tags in the post-synthesis generation of catalysts is exemplified by “clickable” MOFs.…”