Alkali metal cation effects on hydrogen uptake and binding in metal-organic frameworks

A 2-fold interwoven metal-organic framework has been chemically reduced and doped with Li+, Na+, and K+. At low pressures and temperatures, the reduced and doped materials exhibit enhanced H-2 uptake-up to 65% higher than for the neutral framework. Notably, at similar doping levels, H-2 binding is strongest with Li+ and decreases as Li+ > Na+ > K+. However, the uptake increases in the opposite order. We attribute the behavior to structural changes accompanying framework reduction.