Flexible and Hierarchical Metal–Organic Framework Composites for High‐Performance Catalysis

Abstract

The development of porous composite materials is of great significance for their potentially improved performance over those of individual components and extensive applications in separation, energy storage,a nd heterogeneous catalysis.N ow mesoporous metal-organic frameworks (MOFs) with macroporous melamine foam (MF) have been integrated using aone-pot process,generating aseries of MOF/ MF composite materials with preserved crystallinity,hierarchical porosity,a nd increased stability over that of melamine foam. The MOF nanocrystals were threaded by the melamine foam networks,resembling aball-and-stickmodel overall. The resulting MOF/MF composite materials were employed as an effective heterogeneous catalyst for the epoxidation of cholesteryl esters.C ombining the advantages of interpenetrative mesoporous and macroporous structures,t he MOF/melamine foam composite has higher dispersibility and more accessibility of catalytic sites,e xhibiting excellent catalytic performance.Metal-organic frameworks (MOFs) are ac lass of crystalline porous materials that are constructed with metal or metal clusters as nodes and organic ligands as linkers. [1] MOFs are well-known for their extraordinarily high porosity and internal surface areas. [2] Owing to their crystalline and porous structures,M OFs have been widely used in many application, including gas storage, [3] gas separation, [4] heterogeneous catalysis, [5] light emission, [6] drug delivery, [7] and proton conduction. [8] However, most MOFs are rigid, brittle, and very easy to be crumbled. [9] Furthermore,M OFs are insoluble in any solvents and have no exact melting points, which means that they cannot be processed by traditional solvent or heat-based techniques. [10] All of these disadvantages have largely limited their practical applications in various domains.T ot ackle this problem, tremendous efforts have been made to hybridize MOFs with other materials,thus realizing the combination of their advantages and circumventing shortcomings.Avariety of MOF composites have been successfully developed, such as MOF/graphene, [11a] MOF/graphite, [11b] MOF/carbon nanotubes, [11c] MOF/polymers, [11d] MOF/enzymes, [11e] and MOF/metal nanoparticles, [11f] generating new properties unavailable from either component. Very recently,W ang and co-workers successfully developed the MOF/mesh, MOF/cloth, and MOF/sponge composites via the roll-to-roll mechanical production and utilized them for efficient particulate matter removal. [12] Eddaoudi group reported the MOF/silica composite by the stepwise layer-by-layer strategy. [13] TheS ua nd Zhu groups also developed new hierarchical Al-metal-organic aerogels based on ap ost-synthetic process using MOFs and other additives. [14] However, these methods are synthetically tedious and cannot retain the original crystalline morphology of MOFs.W ea im to develop stable MOF/foam composite materials by ao ne-pot procedure,w hich enables the direct preparation of high-quality composite materials.More importantly,this would provide age...

Porosity Engineering of MOF‐Based Materials for Electrochemical Energy Storage

“…Linker design (aspect ratios, substitution, linker exchange) [75,76,79] Metal center design [80,81] Pore partition [77] Mesopores Linker design (elongation, exchange, mixed linkers) [11,85,[87][88][89] Templating (surfactants, block copolymers, self-template) [95,97,99] Defect engineering (chemical etching, thermolysis) [90][91][92][93] Controlled assembly (assembly of nanosized MOFs, assembly in mixed solvents) [94,98] Macropores Templating (Ni foams, Cu foams, polymer sponges) [102][103][104][105] Templating-etching (polystyrene nanospheres) [106] Defect engineering (acid etching) [100][101] Assemble to aerogels [113][114][115][116] 3D printing [117][118][119] Zr. Adapted with permission.…”

“…By replacement of metal foams with flexible and low‐cost polymer sponges (e.g., melamine sponges), ZIF‐8/sponge and PCN‐224(Fe)/sponge have been fabricated by ex situ grafting and in situ growth, respectively. [ 104,105 ] However, the limited loading of MOFs, the presence of exotic skeletons, and the nonordered porous structures of those composites can largely limit the exploration and maximization of the excellent properties of MOFs.…”

Flexible Porous Polynorbornenes with Alkene Linkage for Decolorizing the Highly Reactive Triisocyanate in Ethyl Acetate

“…Porous materials including zeolites, 1,2 metal−organic frameworks (MOFs), 3−6 hydrogen-bonded organic frameworks (HOFs), 7 and porous organic polymers (POPs) 8−10 were endowed with flexibility, and they exhibit some properties (e.g., selectivity, stimuli-induced pore breathing, and reversible phase transformations) that are distinct from their rigid counterparts. 11−13 Benefiting from flexibility and porosity, these porous materials have shown promising applications in gas storage, 14−17 separation, 1,7,18 catalysis, 6,19,20 sensing 13,21,22 and water treatment, 23−26 and targeted delivery of chemicals. 27 In general, the flexibility of POPs can be constructed by those approaches due to flexible building blocks, the presence of flexible pendant groups, and reversible chemical transformations occurring on their building units or even guests and others.…”

“…Porous materials including zeolites, , metal–organic frameworks (MOFs), − hydrogen-bonded organic frameworks (HOFs), and porous organic polymers (POPs) − were endowed with flexibility, and they exhibit some properties (e.g., selectivity, stimuli-induced pore breathing, and reversible phase transformations) that are distinct from their rigid counterparts. − Benefiting from flexibility and porosity, these porous materials have shown promising applications in gas storage, − separation, ,, catalysis, ,, sensing ,, and water treatment, − and targeted delivery of chemicals …”

Facile Bioself-Assembled Crystals in Plants Promote Photosynthesis and Salt Stress Resistance

“…The integration of these foreign materials into biotic systems is nontrivial. , Nanoenabled agriculture allows the use of much smaller active-ingredient inputs than conventional approaches, but these precision agriculture techniques also cause toxicity at a much lower concentration, and nanoparticles (<100 nm) often induce more toxicity than micrometer particles of the same composition . Micron particles have high biocompatibility and catalytic activity. − However, the uptake of micron-sized particles by plants is difficult, hindering related applications. Herein, we propose a concept in which ions are bioself-assembled into micron-sized crystals in plants.…”