After having surveyed literature to the best of my ability, I , humbly, propose two references for your perusal.

[A]CO2(g) adsorbs while CO(g) leaves:

Reference:

Microporous and Mesoporous Materials

Volume 156, 1 July 2012, Pages 217–223

Pls. find its resume as:

For a specified purity of CO2 exiting the packed bed adsorber, the best CO2 removal performance is obtained with CuBTC.

[B] CO(g) adsorbs while CO2(g) leaves:

Reference:

Adsorption

1997, Volume 3, Issue 1, pp 27-32

Pls. find its resume as:

Although zeolites such as NaY and 13X adsorb CO2 much more than CO, the adsorption amount of CO2 and CO can be reversed if the zeolites are modified with CuCl. When zeolite NaY or 13X is mixed with CuCl and heated, high CO adsorption selectivity and capacity can be obtained.

------------------------------------------------------------------------ Using the adsorbent, a single-stage 4 beds PSA process, working at 70°C and 0.4 MPa to 0.013 MPa, CAN OBTAIN CO PRODUCT WITH A PURITY>99.5% AND YIELD >85%.

A mass spec should be able to differentiate between CO and CO2 for analysis, does the CO2 need to be removed?

In our lab we analyze CO in air samples with an MS setup, and we need to remove the CO2 in the sample without affecting CO. We do this by passing the sample through a trap filled with Ascarite followed by Magnesium perchlorate - the Ascarite will trap most CO2 and produce water, then the Mg(ClO4)2 will trap the water. A second trap inserted in liquid nitrogen freezes out the remaining CO2 and H2O.

Note that our sample is atmospheric air, with about 400 ppm CO2 and 200 ppb CO. I'm not sure this method would work with a very different gas matrix.

Manohar, Thanks a lot for your help i'm checking those papers to figure out the best option for my application.

Eric, thanks for your comment. I agree with you the MS does differentiate between CO and CO2 but it doesn't differentiate between the CO in the sample and the CO fragment of the CO2.

Elena,  in my case the CO2 is basically the bulk gas and the CO will be very small but your method is worth to investigate. Many thanks