Engineering Catalysis within a Saturated In(III)-Based MOF Possessing Dynamic Ligand–Metal Bonding

Abstract

Metal–organic frameworks have developed into a formidable heterogeneous catalysis platform in recent years. It is well established that thermolysis of coordinated solvents from MOF nodes can render highly reactive, coordinatively unsaturated metal complexes which are stabilized via site isolation and serve as active sites in catalysis. Such approaches are limited to frameworks featuring solvated transition-metal complexes and must be stable toward the formation of “permanent” open metal sites. Herein, we exploit the hemilability of metal–carboxylate bonds to generate transient open metal sites in an In(III) MOF, pertinent to In-centered catalysis. The transient open metal sites catalyze the Strecker reaction over multiple cycles without loss of activity or crystallinity. We employ computational and spectroscopic methods to confirm the formation of open metal sites via transient dissociation of In(III)–carboxylate bonds. Furthermore, the amount of transient open metal sites within the material and thus the catalytic performance can be temperature-modulated.

Lewis Acid‐Catalyzed Ring‐Opening Alcoholysis of Cyclohexene Oxide: The Role of Open Metal Sites in the Bi(III)‐based Metal‐Organic Framework SU‐101

“…[9] Therefore, MOFs have been investigated in different areas, such as pollutant adsorption, [10] gas detection, [11] and catalysis. [12] Selected MOFs have been used as catalysts for several reactions exhibiting different kinds of active sites, [13] such as single atoms, [14] defect sites, [15] metal clusters, [16] functional groups, [17] and, recently, semi-open metal sites. [18] MOF materials have been applied for gas and liquid phase reaction catalysts with high conversion and successful selectivity.…”

“…MOFs are constructed with metal centers and organic ligands, displaying, in some cases, high thermal and chemical stabilities [9] . Therefore, MOFs have been investigated in different areas, such as pollutant adsorption, [10] gas detection, [11] and catalysis [12] …”

Homogeneous versus MOF-supported catalysis: a direct comparison of catalytic hydroboration with Ni tripodal P3E (E = Si, Ge) complexes

“…11 The enhanced catalytic virtues are attributed to the prevention of active site migration and sintering. 4,8…”

“…Metal-organic frameworks, MOFs, consisting of inorganic nodes and organic linkers forming reticular materials with high surface areas, 1 afford fascinating routes to singlesite heterogeneous catalysts, SSHCs. MOFs are advantageous over other traditional supports in that they provide more extensive scope for structural variation and the opportunity of investigating different platforms, strategies, [2][3][4] and kinetic pathways. 5 Elegant examples of MOF supported SSHCs demonstrate an improvement in the catalytic performance in comparison to their homogeneous counterparts.…”

“…11 The enhanced catalytic virtues are attributed to the prevention of active site migration and sintering. 4,8 Although many SSHCs have been reported as derived from the deposition of organometallic complexes onto MOFs, there are only limited examples of transition metal complexes that bear "tailor-made" ligands which could allow a finer and/or systematic tuning of the steric and electronic properties of the grafted organometallic fragments. 9,12,13 Herein, we present a direct comparison of an organometallic Ni system that is active as a homogeneous catalyst for aldehyde hydroboration and its corresponding MOF grafted heterogeneous counterpart which shows enhanced catalytic properties and recyclability and permits catalysis to be performed under aerobic conditions.…”