Hydrogen storage with spectroscopic identification of chemisorption sites in Cu-TDPAT via spillover from a Pt/activated carbon catalyst

Hydrogen spillover to the Cu-TDPAT (TDPAT = 2,4,6-tris(3,5-dicarboxylphe-nylamino)-1,3,5-triazine) metal-organic framework is probed with adsorption measurements, ex situ characterization techniques, and density functional theory (DFT) calculations. At 1 bar and 300 K, hydrogen chemisorption to Pt/AC/Cu-TDPAT exceeds that expected for physisorption by 8-fold, which is attributable to both catalyst insertion and the creation of structural defects. Hydrogenation of (a) the Cu-O-C bond of the Cu paddlewheel, (b) the sp² N heterocycle, and (c) the secondary amine is demonstrated with ex situ spectroscopy. Exothermic (with respect to H2) hydrogenation at the Cu-O-C bond of the paddlewheel is substantiated by DFT. However, hydrogenated Cu-O-C is metastable, as evidence for dissociation is found at higher temperature (i.e., 473 K H₂). DFT calculations demonstrate hydrogenation of the N groups may occur exothermically only for a charged ligand, suggestive that defects may contribute to hydrogen chemisorption. At high pressure, slow adsorption rates and material instability render the material unsuitable for practical hydrogen storage applications. (Figure Presented).