Experimental Volumetric Hydrogen Uptake Determination at 77 K of Commercially Available Metal-Organic Framework Materials

Abstract

Storage is still limiting the implementation of hydrogen as an energy carrier to integrate the intermittent operation of renewable energy sources. Among different solutions to the currently used compressed or liquified hydrogen systems, physical adsorption at cryogenic temperature in porous materials is an attractive alternative due to its fast and reversible operation and the resulting reduction in storage pressure. The feasibility of cryoadsorption for hydrogen storage depends mainly on the performance of the used materials for the specific application, where metal-organic frameworks or MOFs are remarkable candidates. In this work, gravimetric and volumetric hydrogen uptakes at 77 K and up to 100 bar of commercially available MOFs were measured since these materials are made from relatively cheap and accessible building blocks. These materials also show relatively high porous properties and are currently near to large-scale production. The measuring device was calibrated at different room temperatures to calculate an average correction factor and standard deviation so that the correction deviation is included in the measurement error for better comparability with different measurements. The influence of measurement conditions was also studied, concluding that the available adsorbing area of material and the occupied volume of the sample are the most critical factors for a reproducible measurement, apart from the samples’ preparation before measurement. Finally, the actual volumetric storage density of the used powders was calculated by directly measuring their volume in the analysis cell, comparing that value with the maximum volumetric uptake considering the measured density of crystals. From this selection of commercial MOFs, the materials HKUST-1, PCN-250(Fe), MOF-177, and MOF-5 show true potential to fulfill a volumetric requirement of 40 g·L−1 on a material basis for hydrogen storage systems without further packing of the powders.

GIWAXS Characterization of Metal–Organic Framework Thin Films and Heterostructures: Quantifying Structure and Orientation

“…The α c and µ were estimated based on density values for UiO-67 powder using the GIXA online tool from TU Wien (elaborated on in Section 2.3; Section S7, Supporting Information). [27,28] The lattice parameters for the facecentered cubic structure were based on those presented for the MOF powder by Chai et al [10] From this information, the expected peak positions from this structural hypothesis can be calculated by GIXSGUI and compared to experimental data. The black crosses and corresponding Laue index are shown for the calculated diffraction spot locations in Figure 1f.…”

A database to select affordable MOFs for volumetric hydrogen cryoadsorption considering the cost of their linkers

“…However, the measured hydrogen uptake was lower for this material, considering the actual density of the powders. 31 The material CPM-201 or Mg-BDC shows permanent porosity and could store up to 53 g L À1 of hydrogen after the removal of the dimethylacetamide molecules coordinated to Mg atoms in the cluster. 32 In the same cost-range, the materials MOF-5 and MIL-88B are found, whose permanent porosity has also been corroborated.…”

A database to compare possible MOFs for volumetric hydrogen storage, taking into account the cost of their building blocks

“…The stability to moisture could be higher for Fe-based MOFs Fe6-AzTBC3 (IZENUY) and PCN-250' (TOWPEC) and in Al6-AzBTC3 (JALCAD). The hydrogen uptake of structure PCN-250' was experimentally determined to be up to 53 g/L, considering the measured density of the crystals [101]. Cr-based MIL-88D (YEDKUO) is the structure with the highest calculated volumetric uptake among the four reported structures from 4,4'biphenyldicarboxylic acid (H2bPDC, CAS No.…”

“…Structure UIO-67 (WIZMAV02) is a Zr-based MOF isorreticular to UIO-66 but containing expanded pores resulting in a higher surface area and pore volume. Despite the presence of Zr as metal, poor stability after ambient exposure was detected [101], probably because the used linker is larger than that for UIO-66 [89]. S9) as linker, where Cu-PTz (FUQJUX, see Figure 10) is the one with the highest potential hydrogen storage density up to 51 g/L.…”