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A new type of hierarchically porous carbon (HPC) structures of simultaneously high surface area and high pore volume has been synthesised from carefully controlled carbonization of in-house optimised metal-organic frameworks (MOFs). Changes in synthesis conditions lead to millimetre-sized MOF-5 crystals in a high yield. Subsequent carbonization of the MOFs yield HPCs with simultaneously high surface area, up to 2734 m 2 g À1 , and exceptionally high total pore volume, up to 5.53 cm 3 g À1. In the HPCs, micropores are mostly retained and meso-and macro-pores are generated from defects in the individual crystals, which is made possible by structural inheritance from the MOF precursor. The resulting HPCs show a significant amount of CO 2 adsorption, over 27 mmol g À1 (119 wt%) at 30 bar and 27 C, which is one of the highest values reported in the literature for porous carbons. The findings are comparatively analysed with the literature. The results show great potential for the development of high capacity carbon-based sorbents for effective precombustion CO 2 capture and other gas and energy storage applications. As fossil fuels will continue to dominate the ever increasing energy demand in the coming decades, CO 2 emissions are likely to rise considerably. 1,2 Thus there is a great urgency in cutting down the emissions by carbon (CO 2) capture at anthropogenic point sources 1-4 and effective sorbent materials and methods are highly needed. 2-6 A wide spectrum of materials has been considered for carbon capture by adsorption and/or separation. 5-11 Recently, the physical adsorptive removal of CO 2 by porous solids, such as porous carbons and metal-organic frameworks (MOFs) has attracted much attention. 10-23 Quite a large number of MOFs have been tailor-made and studied extensively for clean energy and environmental applications, including H 2 and CH 4 sorption, storage and separation. 12,13,24-26 Given their structural exibility and thermal stability, lightweight porous carbons have also emerged as promising adsorbents. 11,14-23,27-41 A variety of porous carbons, such as activated,

We report a detailed study of CO2 adsorption in two important metal−organic framework (MOF) compounds (Mg-MOF-74 and HKUST-1). In both MOFs, the open metal ions were identified as the primary binding sites through neutron diffraction measurements. The relatively strong metal−CO2 binding was attributed to an enhanced electrostatic interaction, and vibrational mode analysis shows that the adsorbed CO2 molecule is strongly attached through one of its oxygen atoms while the rest of the molecule is relatively free. This high orientational disorder is the reason for the large apparent O−C−O bond bending angle derived from diffraction measurements. Our calculations give only a small degree of bond bending, suggesting that the CO2 adsorption on the open metal site is still largely physisorption. Interestingly, the overall metal−CO2 binding strength is right in the range which can facilitate both adsorption (CO2 capture) and desorption (MOF regeneration) under typical flue gas conditions.