A Simple, Transition Metal Catalyst-Free Method for the Design of Complex Organic Building Blocks Used to Construct Porous Metal-Organic Frameworks

The design of metal-organic frameworks (MOFs) having large pore sizes and volumes often requires the use of complex organic ligands, currently synthesized using costly and time-consuming palladium-catalyzed coupling chemistry. Thus, in the present work, a new strategy for ligand design is reported, where piperazine and dihydrophenazine units are used as substitutes for benzene rings, which are the basic building block of most MOF ligands. This chemistry, which is based on simple, nucleophilic aromatic substitution (SNAr) reactions, is used for the transition metal catalyst-free construction of 21 new, carboxylate-based ligands with varying sizes, shapes, and denticity and 15 linear di- and tetra-nitriles. Moreover, to demonstrate the utility of the ligands as building blocks, 16 new structurally diverse MOFs having surface areas up to 3100 m(2) g(-1) were also synthesized.

Automated summary

In this work, a new strategy for ligand design is proposed, using piperazine and dihydrophenazine units as substitutes for benzene rings, via simple nucleophilic aromatic substitution reactions without using transition metal catalysts. 21 carboxylate-based ligands with varying sizes, shapes, and denticity and 15 linear di- and tetra-nitriles were successfully synthesized. Moreover, 16 structurally diverse MOFs with surface areas up to 3100 m(2) g(-1) were synthesized using these ligands as building blocks.