A Cao adsorbent was modified using an organic aluminum precursor to enhance its adsorption capacity during cyclic CO2 greenhouse gas capture. During cyclic adsorption test, the Al-modified CaO adsorbent with 5 wt % Ca12Al14O33 (CaAl(95)) adsorbent had a better adsorption capacity than the un-modified CaO. From 5 to 60 cycles, the CO2 adsorption capacity of CaAl(95) was about 20% higher than that of CaO adsorbent. At 66th cycle, the adsorption time was extended to 1 hr, the CO2 adsorption capacity of CaAl(95) was 25% higher than that of CaO adsorbent. Thus, the required quantity of CaO adsorbent could be significantly reduced. The CO2 capture efficiency of CaAl(95) was also higher than that of the un-modified CaO adsorbent. With an empty bed residence time of 0.0074 sec, the CO2 capture efficiency was 63-74% over 20 cyclic adsorption tests. This is an abstract of a paper presented at the 101st AWMA Annual Conference and Exhibition (Portland, OR 6/24-27/2008).