Lewis Acid Activation of a Hydrogen Bond Donor Metal–Organic Framework for Catalysis

Abstract

A new metal–organic framework (MOF) composed of urea-containing tetracarboxylate struts was synthesized, and its hydrogen bonding capabilities were evaluated. The catalytic performance of this heterogeneous framework is enhanced through preactivation with silyl Lewis acids, leading to Friedel–Crafts reaction rates greater than those of common homogeneous hydrogen bond donors.

Crystallographic investigation into the self-assembly, guest binding, and flexibility of urea functionalised metal-organic frameworks

“…For example, grafting hydrogen bond donor functionality, such as amides (11)(12)(13)(14)(15)(16)(17)(18)(19)(20), ureas (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), thioureas (33), and squaramides (34)(35)(36), (Figure 1(a)) onto the organic scaffold of the MOF can enhance properties including carbon dioxide capture (13,15,17,18), anion binding (20,21), sensing (28), and organocatalytic activity (6). Urea-functionalised MOFs in particular have been found to catalyse FriedelCrafts reactions between pyrroles and nitroalkenes (22,24,27,29,31), Henry reactions between aldehydes and nitromethane (23), and the methanolysis of epoxides (25).…”

“…Urea-functionalised MOFs in particular have been found to catalyse FriedelCrafts reactions between pyrroles and nitroalkenes (22,24,27,29,31), Henry reactions between aldehydes and nitromethane (23), and the methanolysis of epoxides (25).…”

Potential Utilization of Metal–Organic Frameworks in Heterogeneous Catalysis: A Case Study of Hydrogen‐Bond Donating and Single‐Site Catalysis

“…Later, in the same year, Scheidt et al. reported new urea‐containing heterogeneous MOF scaffold (NU‐GRH‐1 ) which was composed by urea‐based tetracarboxylate struts ( L ), 4,4′‐dipyridyl (BPy) and Zn metal ion (Figures 6 a and b) . The highlight of work is the enhancement of the urea catalytic activity through pre‐activating the NU‐GRH‐1 MOF with silyl Lewis acid and thereby accomplish the greater Friedel–Crafts reaction rates as compared to common homogeneous urea catalysts.…”

Acid-Base Bifunctional Microporous Organic Nanotube Networks for Cascade Reactions

“…In such a situation, heterogeneous catalysts which have advantages of easier recycling and better stability of antagonist functional groups have recently attracted much attention from researchers. During the past decade, porous materials such as zeolites, [23,24] silicas, [25][26][27][28][29][30] metal-organic frameworks, [31][32][33][34][35] and porous organic polymers [36][37][38][39][40][41][42] have been extensively employed as heterogeneous catalysts supports. For example, Thiel and co-workers reported functionalized periodic mesoporous organosilica in which the acidic groups were located in the framework walls and the basic groups were directed into the channel pores.…”