“…17 Subsequently, a variety of pristine MOFs (such as ZIF-8, 18 MOF-200, MOF-210, 19 NU-100, IRMOF-20, 20 UIO-66, 21 SNU-200, 22 NaNi 3 (OH)(SIP) 2 , 23 DUT-4, 24 etc.) have been exploited as hydrogen storage adsorbents at 77 K. The hydrogen storage capacity can be further improved through introducing appropriate numbers of "guest" metal ions (Co 2+ , Cu 2+ , Fe 2+ , Zn 2+ , Li + , Na + , and K + ) [25][26][27] and organic ligands 28,29 into MOFs, which is proposed due to the increasing unsaturated metal sites, modiable electrostatic eld or adjustable surface area and pore volume of the MOFs. Furthermore, Pd NPs can effectively enhance the operation temperature of materials' hydrogen storage and hydrogen uptake due to hydrogen spillover and formation of Pd hydride, which will reduce the cost of industrial hydrogen storage.…”