Adsorption (2008) 14: 755–762 DOI 10.1007/s10450-008-9137-6 Amine functionalised metal organic frameworks (MOFs) as adsorbents for carbon dioxide Bjørnar Arstad · Helmer Fjellvåg · Kjell Ove Kongshaug · Ole Swang · Richard Blom Received: 3 December 2007 / Revised: 30 May 2008 / Accepted: 20 June 2008 / Published online: 17 July 2008 © Springer Science+Business Media, LLC 2008 Abstract Three different porous metal organic framework (MOF) materials have been prepared with and without un- coordinated amine functionalities inside the pores. The ma- terials have been characterized and tested as adsorbents for carbon dioxide. At 298 K the materials adsorb significant amount of carbon dioxide, the amine functionalised adsor- bents having the highest CO 2 adsorption capacities, the best adsorbing around 14 wt% CO 2 at 1.0 atm CO 2 pressure. At 25 atm CO 2 pressure, up to 60 wt% CO 2 can be adsorbed. At high pressures the CO 2 uptake is mostly dependent on the available surface area and pore volume of the material in question. For one of the iso-structural MOF pairs the intro- duction of amine functionality increases the differential ad- sorption enthalpy (from isosteric method) from 30 to around 50 kJ/mole at low CO 2 pressures, while the adsorption en- thalpies reach the same level at increase pressures. The high pressure experimental results indicate that MOF based solid adsorbents can have a potential for use in pressure swing adsorption of carbon dioxide at elevated pressures. Keywords Metal organic frameworks · Amine functionality · Carbon dioxide · Adsorption B. Arstad · O. Swang · R. Blom ( ) SINTEF Materials and Chemistry, P.O. Box 124, Blindern, 0314 Oslo, Norway e-mail: Richard.Blom@sintef.no H. Fjellvåg · K.O. Kongshaug Centre for Materials Science and Nanotechnology and Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway 1 Introduction At present, CO 2 is separated from low pressure flue gases or from high pressure natural gas by using a liquid or solu- tion as absorbent (Nunge and Gill 1963). The process typi- cally works in the temperature interval between 313 K (ab- sorption) and 393 K (desorption). Main drawbacks of the solvent based absorption processes are high energy require- ments and possible environmental issues due to loss of alka- nolamine as a consequence of its high volatility. Separa- tion processes based on solid sorbents might be an alterna- tive, and during the last decade a number of silica, zeolite, carbon and polymer based sorbents have been developed (Leal et al. 1995; Xu et al. 2002; Kim et al. 2005; Harlick and Sayari 2006; Huang et al. 2003; Delaney et al. 2002; Zheng et al. 2005; Hiyoshi et al. 2005; Khatri et al. 2005; Chang et al. 2003; Siriwardane et al. 2001; Harlick and Tezel 2004; Satyapal et al. 2001). However, a main drawback of many of these is their relatively limited surface areas, their limitation in structural design, and the limited possibility for surface modification. Metal organic frameworks (MOFs, also called coordi- nation polymers) are a relatively new class of porous ma- terials with high diversity. Such materials are built up by metal atoms (ions) linked together by multifunctional or- ganic ligands. The high diversity is a consequence of the linkage between the inorganic and organic chemistry where the whole substitution chemistry of organic synthesis can be coupled with the inorganic elemental and cluster chem- istry. During the 1990s the field has developed on the acad- emic level (Hagrman et al. 1999; Batten and Robson 1998; Zaworotko 2000; James 2003; Kitagawa et al. 2004). Dur- ing the last years couple of years MOF materials has been tested for applications such as gas storage (Noro et al. 2000;