A New Zinc-Based Metal-Organic Framework for Catalytic Synthesis of N-Substituted Pyrroles

A new zinc-based metal-organic framework (MOF) Zn-2(OAB) [OAB(4-)=4,4 '-(oxalylbis(azanediyl))bis(2-oxidobenzoate)), analogous to a well-studied MOF-74 structure, was solvothermal synthesized and characterized. The Zn-2(OAB) frameworks exhibited accessible mesopore channels (24 angstrom) and high porosity (S-BET=3115 m(2) g(-1)). The presence of the high density of both Lewis acidic Zn sites and -NH- groups derived from the organic OAB(4-) unit make Zn-2(OAB) a promising candidate for catalysis Paal-Knorr N-substituted pyrroles synthesis. As such, Zn-2(OAB) exhibited excellent catalytic activity in the synthesis of 2,5-dimethyl-1-phenyl-1H-pyrrole with a yield of 96 % at 70 degrees C for 16 min. Notably, the catalytic activity of Zn-2(OAB) outperformed that of homogeneous, heterogeneous catalysts, and representative Zn-based MOFs (ZIF-8, MOF-5, Zn-MOF-74). The Zn-2(OAB) was also demonstrated to be reused up to eight times without noteworthy loss of its activity.