Molecular Catalysis of Energy Relevance in Metal–Organic Frameworks: From Higher Coordination Sphere to System Effects

Abstract

The modularity and synthetic flexibility of metal–organic frameworks (MOFs) have provoked analogies with enzymes, and even the term MOFzymes has been coined. In this review, we focus on molecular catalysis of energy relevance in MOFs, more specifically water oxidation, oxygen and carbon dioxide reduction, as well as hydrogen evolution in context of the MOF–enzyme analogy. Similar to enzymes, catalyst encapsulation in MOFs leads to structural stabilization under turnover conditions, while catalyst motifs that are synthetically out of reach in a homogeneous solution phase may be attainable as secondary building units in MOFs. Exploring the unique synthetic possibilities in MOFs, specific groups in the second and third coordination sphere around the catalytic active site have been incorporated to facilitate catalysis. A key difference between enzymes and MOFs is the fact that active site concentrations in the latter are often considerably higher, leading to charge and mass transport limitations in MOFs that are more severe than those in enzymes. High catalyst concentrations also put a limit on the distance between catalysts, and thus the available space for higher coordination sphere engineering. As transport is important for MOF-borne catalysis, a system perspective is chosen to highlight concepts that address the issue. A detailed section on transport and light-driven reactivity sets the stage for a concise review of the currently available literature on utilizing principles from Nature and system design for the preparation of catalytic MOF-based materials.

Electrochromism in Isoreticular Metal–Organic Framework Thin Films with Record High Coloration Efficiency

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Chiral lanthanide–silver(i) cluster-based metal–organic frameworks exhibiting solvent stability, and tunable photoluminescence

“…Metal–organic frameworks (MOFs), as a kind of porous material, have garnered significant attention in materials science, 1 chemistry 2 and energy-related research, 3 and have been extensively studied in the fields of gas adsorption and separation, 4 catalysis, 5,6 drug delivery, etc . 7,8 Generally, MOFs are constructed by connecting metal ions and organic ligands via coordination bonds.…”

Engineering a molecular ruthenium catalyst into three-dimensional metal covalent organic frameworks for efficient water oxidation

“…One is based on the post-synthetic immobilization of molecular WOCs onto a heterogeneous support such as the metal organic frameworks. 22,23 Another is a host–guest approach to encapsulate molecular WOCs in a porous host. 24–26 However, in the aforementioned integrated system, the amount and position of the catalytic centers cannot be precisely controlled, and the active sites are often poorly accessible.…”