Optimization of the Pore Structures of MOFs for Record High Hydrogen Volumetric Working Capacity

• Published in: Advanced materials (Weinheim) Vol. 32; no. 17; pp. e1907995 - n/a
• Main Authors: Zhang, Xin, Lin, Rui‐Biao, Wang, Jing, Wang, Bin, Liang, Bin, Yildirim, Taner, Zhang, Jian, Zhou, Wei, Chen, Banglin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.04.2020
• Subjects: Activated carbon; Adsorption; Empirical equations; Hydrogen; Hydrogen storage; Materials science; Mathematical analysis; Metal-organic frameworks; metal–organic frameworks (MOFs); Optimization; pore geometry; pore occupancy; Pore size; Porosity; Storage capacity; Work capacity; Zirconium; pore geometry; empirical equations; pore occupancy; metal-organic frameworks (MOFs); hydrogen storage
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201907995

Metal–organic frameworks (MOFs) are promising materials for onboard hydrogen storage thanks to the tunable pore size, pore volume, and pore geometry. In consideration of pore structures, the correlation between the pore volume and hydrogen storage capacity is examined and two empirical equations are rationalized to predict the hydrogen storage capacity of MOFs with different pore geometries. The total hydrogen adsorption under 100 bar and 77 K is predicted as ntot= 0.085× Vp − 0.013× Vp2 for cage‐type MOFs and ntot= 0.076× Vp − 0.011× Vp2 for channel‐type MOFs, where Vp is the pore volume of corresponding MOFs. The predictions by these empirical equations are validated by several MOFs with an average deviation of 5.4%. Compared with a previous equation for activated carbon materials, the empirical equations demonstrate superior accuracy especially for MOFs with high surface area (i.e., SBET over ≈3000 m2 g−1). Guided by these empirical equations, a highly porous Zr‐MOF NPF‐200 (NPF: Nebraska Porous Framework) is examined to possess outstanding hydrogen total adsorption capacity (65.7 mmol g−1) at 77 K and record high volumetric working capacity of 37.2 g L−1 between 100 and 5 bar at 77 K. Two empirical equations to predict hydrogen storage capacity are rationalized for cage‐type and channel‐type metal–organic frameworks (MOFs) with superior prediction accuracy than the established equation. Guided by these new equations, a cage‐type Zr‐MOF NPF‐200 (NPF: Nebraska Porous Framework) is evaluated and found to possess record high volumetric working capacity (37.2 g L−1) between 100 and 5 bar at 77 K.