Synthesis and Functionalization of Oriented Metal–Organic‐Framework Nanosheets: Toward a Series of 2D Catalysts

Abstract

3268 wileyonlinelibrary.com inorganic nodes in MOFs can be intrinsic active sites for catalysis, e.g., copperbased MOFs have been demonstrated as an excellent solid Lewis acid catalyst for a few reactions; [ 4,7 ] (ii) extrinsic functional species (e.g., nanoparticles) can be introduced to MOFs structure, either on the external surfaces or inside the bulks or shells of MOFs. Various catalytic nanoparticles have been successfully incorporated into different MOFs matrices, including Au, Ag, Pt, Cu, or their combination etc.; [8][9][10] and (iii) MOFs also serve as solid precursors for metal or metaloxide catalysts due to their high metal density within the frameworks and easy transformation. Many porous transition metal oxides, such as CuO, Cu 2 O, Mn 2 O 3 , Mn 3 O 4 , Co 3 O 4 , and ZnO among others, have been derived through thermolysis under controlled atmospheres. [11][12][13][14][15][16] For example, porous CuO hollow architectures with perfect octahedral shape were prepared by annealing HKUST-1 precursor in fl owing air. [ 12 ] Moreover, zeolitic imidazolate framework-67 (ZIF-67) was used to design and generate Co 3 O 4 or structurally more complex Co 3 O 4 /NiCo 2 O 4 . [ 13,14 ] Although increasing research attention has been paid to the catalytic applications of MOFs, to our knowledge, shapes of the studied MOFs are mostly followed in 3D isotropic polyhedrons (i.e., high symmetric MOF crystals with sizes greater than 100 nm), and the catalytic systems derived from MOFs with anisotropic shapes such as nanofi bers or nanosheets with a dimension(s) less than 10 nm have seldom been explored.Similar to many inorganic nanomaterials, tailoring of size and shape is essential to customize MOFs for specifi c applications according to the principle of "structure dictates function." [ 17 ] Although a fi ne control over the size and size-distribution of MOFs has been realized, e.g., in the range of 100 nm to several micrometers, [ 18 ] fashioning MOFs into desired shapes for specifi c applications remain to be challenging. Nevertheless, several attempts to the architectural control of MOFs shapes have recently appeared in the literature, ranging from 1D, 2D to 3D nanostructures. [ 19,20 ] For example, nanosheets of MOFs as molecular sieving membranes for gas separation have been made in two recent reports, [ 21,22 ] which achieved much higher separation selectivity than MOFs in other

Structural Engineering of Low‐Dimensional Metal–Organic Frameworks: Synthesis, Properties, and Applications

“…Sci. This strategy has been also used for the preparation of MOF nanosheets [50,[165][166][167] Zhang and co-workers synthesized a series of tetrakis(4-carboxyphenyl)porphyrin (TCPP) based ultrathin 2D MOFs through a surfactant-assisted method, such as Zn-TCPP, Cu-TCPP, Cd-TCPP, Co-TCPP(Fe), Cu-TCPP(Fe), Zn-TCPP(Fe), and PPF-3 nanosheets. The key of this method is to inhibit the growth of crystal in a certain direction.…”

“…[125] Moreover, 2D MOF nanosheets have been also widely used in catalysis. [59,165,302] Recently, Lin and co-workers reported a series of 2D metal-organic layers, i.e., Fe-TPY/ Zr-BTB MOL, [64] CoCl 2 /Hf-TPY MOL, [178] FeBr 2 /Hf-TPY MOL, [178] which are efficient heterogeneous catalysts for various organic reactions, including hydrosilylation of terminal olefins, CH amination benzylic, CH borylation. [301] Zr-porphyrinic MOF nanosheets with thickness of ≈1.48 nm exhibited excellent photocatalytic performance for the oxidation of 1,5-dihydroxynaphthalene, which is owing to their highly exposed active sites and unique properties of porphyrin units.…”

Two‐Dimensional Metal–Organic Framework Nanosheets

“…Incorporating 2D MOF nanosheets with other materials is an efficient way to prepare multifunctional composites that possess new properties superior to those of the individual components . Recently, noble metals, metal sulfide, and carbon nanomaterials have been incorporated with 2D MOF nanosheets to develop composite nanosheets, which might combine the merits and mitigate the shortcomings of the individual components. Importantly, the synergetic effect due to the interaction between each component can lead to improved performance compared to the individual components.…”

A Surfactant‐Free and Scalable General Strategy for Synthesizing Ultrathin Two‐Dimensional Metal–Organic Framework Nanosheets for the Oxygen Evolution Reaction

“…[17] Some bottom-up synthesis strategies have been developed to restrict the vertical growth of the MOFs,but each of them still has disadvantages. [20] But it can only give limited types of MOF nanosheets owing to the intrinsic structure (interaction between layers) of MOFs.A lternatively,t he usage of some organic reagents,s uch as poly(vinylpyrrolidone) (PVP), [6] 4,4'-bipyridine, [21] pyridine, [22] formic acid, [23] and 2-aminoterephthalic acid, [24] can modulate the growth of free-standing 2D MOF nanosheets.W ith the modulation of PVP,t he Cu 2 Oc ubic can even be transformed into Cu-(HBTC)-1 [25] and Cu-BDC [26] nanosheets through hydrothermal reaction with 1,3,5-benzenetricarboxylic acid (H 3 BTC) and benzene-1,4-dicarboxylic acid (H 2 BDC), respectively. [20] But it can only give limited types of MOF nanosheets owing to the intrinsic structure (interaction between layers) of MOFs.A lternatively,t he usage of some organic reagents,s uch as poly(vinylpyrrolidone) (PVP), [6] 4,4'-bipyridine, [21] pyridine, [22] formic acid, [23] and 2-aminoterephthalic acid, [24] can modulate the growth of free-standing 2D MOF nanosheets.W ith the modulation of PVP,t he Cu 2 Oc ubic can even be transformed into Cu-(HBTC)-1 [25] and Cu-BDC [26] nanosheets through hydrothermal reaction with 1,3,5-benzenetricarboxylic acid (H 3 BTC) and benzene-1,4-dicarboxylic acid (H 2 BDC), respectively.…”