Here we show the crucial role of ultramicropores on the adsorbed H-2 amount. By synthesizing Fe-BTCs via a perturbation assisted nanofusion synthesis strategy and by the control of textural porosity via Fe:BTC ratio, BET surface area (1312 m(2)/g), total pore volume (1.41 cm(3)/g), and H-2 adsorption capacity (1.10 wt% at 7.6 bar and 298 K) were enhanced by 1.6, 3.1, and 2.6 times, respectively. The reported BET surface area, and the total pore volume are the highest of those reported for Fe-BTC, to date. The enhanced H-2 adsorption capacity of Fe-BTC-3 is attributed to the ultramicropores present in its pore structure. Presence of ultramicropores maximizes van der Waals potential, and the adsorbed H-2 amount increases. By the perturbation assisted nanofusion synthesis strategy and the control over textural porosity, an Fe-BTC that possesses a H-2 adsorption capacity higher than those of reported MOFs with higher BET surface areas has been reported. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.