Iodine Molecules within Triethylenediamine-Based Metal–Organic Frameworks for Hydrolysis/Alkylation Tandem Reactions

Abstract

The integration of radionuclide iodine molecules in metal−organic frameworks (MOFs) for organic synthesis is attracting considerable research attention due to their specific catalytic performance. However, understanding the comprehensive catalytic behaviors of different types of molecular iodine encapsulated in MOFs for a sequential organic transformation is a great challenge. To address this issue, we have designed two triethylenediamine-functionalized MOFs assembled from 1,3,5-tricarboxyphenyl-2-(triethylenediaminemethyl)benzene-linker and {Cd-(COO) 3 N} or {Cu 4 (u 3 -OH) 2 (COO) 6 N} clusters. Both MOFs show good stability and adsorption of I 2 in the solution and vapor phases. Catalysts obtained after treatment with ethyl acetate present efficient catalytic activity in hydrolysis/alkylation tandem reactions in water. The mechanistic investigations disclose a sequential catalytic process comprising a "hidden" Brønsted acid catalytic hydrolysis of acetals to aldehydes followed by the I 2 -bonding Lewis acid catalytic alkylation of aldehydes to 3,3′-disubstituted 1H-indoles.

Mechanistic Insights into a Co(II)-Coordinated “Free” Metal Site of 2D Zinc-Based MOFs for β-Alkylation of Secondary Alcohols with Primary Alcohols

“…Metal–organic framework (MOF)-based materials, especially for functional MOFs with unsaturated coordination metal sites and functional organic ligand, have long been a research hotspot in the field of catalysis due to unique properties. − Because the presence of unsaturated coordination metal sites in MOF structures enables the effective fixation of introduced metals onto the ligands, thereby enhancing the stability of the metal introduced in the catalyst preparation process and minimizing the loss of active components during the reaction. Moreover, of utmost importance is that MOF structures containing these unsaturated coordination sites can selectively coordinate with different active metals to prepare catalysts with varying activities for catalyzing different organic reactions. − This feature allows the prepared MOF materials with unsaturated coordination sites to serve as universal templates, simplifying the catalyst preparation process and ultimately improving the overall efficiency of the catalytic process. − Furthermore, this aligns with the current goal of achieving carbon neutrality. Therefore, the development of MOFs as carriers for the preparation of efficient catalysts supported by MOFs has become crucial in heterogeneous catalytic reactions …”

Multifunctional Metal‐Organic Frameworks as Catalysts for Tandem Reactions

“…In addition, Liao et al have prepared the iodine installed MOFs composites, which also exhibited high catalytic activity for tandem reactions. [38] Specifically, the authors synthesized two MOFs (Cd-MOF and Cu-MOF) from triethylenediamine (DABCO) groups decorated tricarboxylic acid ligands and metal salts (i. e., CdCl 2 • 6H 2 O or Cu(NO 3 ) 2 • 6H 2 O) under solvothermal conditions. Both MOFs exhibit high adsorption capacity for I 2 .…”

“…I 2 -uptake MOFs were used to catalyze the hydrolysis/alkylation tandem reaction. Reproduced with permission from ref [38]…”