Post-Synthesis Amine Borane Functionalization of a Metal-Organic Framework and Its Unusual Chemical Hydrogen Release Phenomenon

5 years ago

Post-Synthesis Amine Borane Functionalization of a Metal-Organic Framework and Its Unusual Chemical Hydrogen Release Phenomenon

Thomas Fox, Heinz Berke, Yigang Yan, Jürg Hutter, Arndt Remhof, Olivier Blacque, Marcella Iannuzzi, Ralph Koitz, Samir Barman, Andreas Züttel

A novel strategy for post-synthesis amine borane functionalization of MOFs under gas-solid phase transformation, utilizing gaseous diborane, is reported. The covalently confined amine borane derivative decorated on the framework backbone is stable when preserved at low temperature, but spontaneously liberates soft chemical hydrogen at room temperature, leading to the development of an unusual borenium type species (-NH=BH2+) ion-paired with a hydroborate anion. Furthermore, the unsaturated amino borane (-NH=BH2) and the μ-iminodiborane (-μ-NHB2H5) were detected as final products. A combination of DFT based molecular dynamics simulations and solid state NMR spectroscopy, utilizing isotopically enriched materials, were undertaken to unequivocally elucidate the mechanistic pathways for H2 liberation. Rapid chemical tuning: A novel strategy for rapid post-functionalization of MOFs under gas-solid phase reaction conditions by diborane is revealed, which paves the way to chemically tune surface adorned pendant amine groups with amine borane functionalities confined in ‘‘splendid-isolation‘‘ exhibiting unusual chemical/physical attributes. Thus, promoting at ambient conditions H2 evolution and generation of H2-depleted ‘‘transient-yet-stable‘‘ unsaturated B,N-containing species.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702013