A metal–organic framework as a chemical guide to control hydrogen desorption pathways of ammonia borane

Abstract

We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption.

Insight into the Catalytic Effects of Open Metal Sites in Metal–Organic Frameworks on Hydride Dehydrogenation via Nanoconfinement

“…It was reported that AB impregnated in MOF-5 demonstrated reduced T d and E a due to the nanoconfinement phenomenon. 29,30 On the other hand, several publications claim to have AB confined in MOFs by physical milling method. For instance, Wang et al attributed improved dehydrogenation properties of AB@MOF to nanoconfinement effect.…”

“…Applying MOFs to AB nanoconfinement, for example, with chemical deliquesce method, in which AB crystals are dissolved in solution blending with suspended MOFs and further recrystallized after solvent removal, the AB@MOF composites desorb hydrogen at lowered temperature with improved kinetics compared to neat AB. It was reported that AB impregnated in MOF-5 demonstrated reduced T d and E a due to the nanoconfinement phenomenon. , On the other hand, several publications claim to have AB confined in MOFs by physical milling method. For instance, Wang et al attributed improved dehydrogenation properties of AB@MOF to nanoconfinement effect .…”

Improved hydrogen release from ammonia borane confined in microporous carbon with narrow pore size distribution

“…4,5 However, despite these merits, there are technical barriers preventing AB to be practically used as an on-board energy source, such as its slow thermal kinetics below 100 C and unwanted by-products including ammonia (NH 3 ), diborane (B 2 H 6 ), and borazine (B 3 H 6 N 3 ), which will poison the catalyst in a proton membrane fuel cell. 2,3,[6][7][8] To date, a number of ways have been investigated to tackle the above mentioned issues including the use of metal catalysts 3,[9][10][11][12][13][14][15][16][17] or metal-free catalysts, [18][19][20] the formation of metal hydrides, [21][22][23] the realisation of metal or methane substitution, [24][25][26] the utilisation of ionic liquid, 27,28 additives, 29,30 or nanoconfinement 8,[31][32][33][34][35][36][37][38][39][40] etc. Significant improvements on lowering the hydrogen release temperatures, improving the kinetics and avoiding the emissions of those harmful by-products have been made.…”

Improved thermal dehydrogenation of ammonia borane by MOF-5

“…14,23 Jeong, H. M. and colleagues reported an AB@MOF-5 thermal dehydrogenation system, but release of NH 3 was not described and the important effect of the unsaturated coordinated metal sites of MOFs in the AB-MOF system was not mentioned. 26 However, the formation of NH 3 is an important issue because even a small amount of NH 3 poisons the catalysts of proton exchange membrane fuel cells.…”