Enhancement of catalytic activity for hydrogenation of nitroaromatic by anionic metal-organic framework

Nitroaromatic hydrogenation catalysis without precious metals remains a longstanding challenge. The rate of electron transfer is the crucial factor affecting hydrogenation catalysis. Herein, an ionic Cd-based metal-organic framework (I-Cd-MOF) exhibiting a unique structure with one-dimensional (1D) opening nanochannels and good electron transfer ability was synthesized for catalyzing hydrogenation of 4-nitrophenol (4-NP). The catalytic activity of the unique I-Cd-MOF without noble metals is detected, which is higher than most reported noble metal catalysts. Remarkably, the reaction rate of I-Cd-MOF (4.28 min−1) is about 47.6 times higher than that of the Cd-based neutral MOF (N-Cd-MOF) with the similar crystalline structure. Liquid chromatograph mass spectrometer (LC-MS) and theoretical results demonstrate that 4-NP and five intermediates are stabilized in the channels of I-Cd-MOF, which increases the possibility of contact with H* and H2 generated at the Cd sites. The I-Cd-MOF was extended to other nitroaromatic hydrogenation catalysis, which still displays excellent activity. More importantly, the I-MOF@Filter membrane was successfully constructed for continuous hydrogenation catalytic reactions, which maintains a high catalytic performance after 7 cycles of recycling without washing. This work fills in the application of the I-MOFs in hydrogenation catalytic reactions and provides an effective way for the rapid and green degradation of nitroaromatic compounds.