The tree biomass acacia gum was used as a natural precursor to synthesize microporous carbon for energy storage application. The microporous carbons were synthesized by hydrothermal carbonization of acacia gum at 180 degrees C, and subsequent activation by KOH at temperatures in the range of 700-900 degrees C. The carbon materials possess high surface area and well-controlled pore size distribution. Moreover, the porosity can be finely tuned by modifying the activation temperatures. The influence of the porosity of the carbon materials on their capacitive performance was investigated. The superior charge storage capability with specific capacitance up to 272 F g(-1) at current density of 1 A g(-1) in 6 M KOH was achieved by the as-prepared microporous carbons. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.