Chemical Reactions at Isolated Single-Sites Inside Metal–Organic Frameworks

Abstract

Isolated, coordinatively unsaturated metal sites within metal-organic framework (MOF) materials feature interesting chemical properties and offer applications as single-site catalysts. Here, we report on the recent progress in providing fundamental insight into chemical reactions occurring inside MOFs. In addition to the common form, powders, we discuss the potential of MOF thin films (SURMOFs). The combined spectroscopic and modeling approach applied to selected systems demonstrated that the catalytic activity of MOFs can be precisely tuned. A particular interesting case is the so-called defect-engineering, where structural imperfections are created in a controlled fashion. The chemical properties of MOF materials can be further modified by integration and decoration of linkers or loading with guest species, such as metal or metal-oxide nanoparticles or nanoclusters. A particularly interesting aspect of layer-by-layer approaches for the fabrication of MOF thin films is the prospect to realize tandem catalysts. Graphical AbstractKeywords Metal-organic frameworks · Thin films · Single-site catalysts · Infrared spectroscopy · Defects · Active sites

Isolating reactive metal-based species in Metal–Organic Frameworks – viable strategies and opportunities

“…gas adsorption), and the structural characterisation of small organic molecules bound within their pore network. Given the breadth of these topics and signicant attention they have received, we have specically excluded this work, and direct the reader to relevant contributions on small molecule characterisation at coordinatively unsaturated nodes in MOFs 38,[48][49][50] and work regarding structural characterisation of small molecules in frameworks. 34,36 Finally, we would like to clarify the term 'reactive species'; reactive, like the term 'stable', is widely used but oen not well dened.…”

The Surface Chemistry of Metal Oxide Clusters: From Metal–Organic Frameworks to Minerals

“…Rates of ligand exchanges in POMs are sensitive to both the metal in the clusters and the ligands, and the same is true for MOF nodes. 113 Thus, MOFs incorporating high-valent metal ions form strong coordination bonds with linkers for good MOF stability, 114 and MOFs having nodes that incorporate metals with variable oxidation states, like POMs, are active for catalytic redox reactions, 115 offering rich opportunities for discovery. 104 , 116 Heterometal or anion substitution into Keggin ions profoundly affects stabilities and reactivities, particularly when those substitutions are into sites that strongly influence the metastable equilibria with defective forms.…”

Two-dimensional metal–organic frameworks and their derivatives for electrochemical energy storage and electrocatalysis

“…electrochemical energy storage materials and electrocatalysts) with sufficient ion storage sites, excellent ion diffusion ability, high conductivity, and abundant active catalytic sites is vital but challenging. [4][5][6] Metal-organic frameworks (MOFs), a series of crystalline materials consisting of metal ions and organic ligands, 7,8 have been extensively investigated for electrochemical energy storage [9][10][11] and electrocatalysis [12][13][14][15] due to their abundant active sites, tunable pore distribution, and controllable morphologies 7,[16][17][18][19][20][21][22][23] Beneting from the ordered arrangement of the metal ions and organic linkers in the MOFs, the MOF derivatives tend to show a homogeneous distribution of the metal atoms or/and metal nanoparticles, 24,25 which could enhance the metal utilization efficiency 26 and further leads to a great improvement for their applications in energy storage and electrocatalysis. To date, carbon materials, 27 metals, 28 transition metal oxides, 25,29,30 transition metal carbides, 31 transition metal dichalcogenides, 32,33 transition metal phosphides, [34][35][36] and their composites 37 have been successfully fabricated from MOF precursors.…”