Reactions of laser-ablated Nb atoms with CO2 give insertion products ONbCO and O2Nb(CO)(2) and the negative species O2Nb(CO)(2)(-), which have been identified by matrix isolation FTIR method and DFT calculations. Two ONbCO structural products (I and II) were observed with infrared absorptions at 1902.6/960.1 and 1821.3/915.6 cm(-1), respectively. UV light irradiation destroyed the O2Nb(CO)(2)(-) anion completely, while the intensities of ONbCO(II) and O2NbCO were enhanced markedly. Sample annealing led to the obvious increase of ONbCO(II), while the ONbCO(I) can further combine with CO2 to form O2Nb(CO)(2).