Because TiN is dispersed and mixed with PEI in the TiN-contactor system, it is expected that the powderof NP-only gives rise to higher temperature. However, the pristine contactor system has a high IR emissivity (~0.8-0.95), and we expect the measured temperature of the composite system ~110°C to be more accurate, and therefore the photo-induced heating to be compatible with the stability window of PEI. While the plasmonic community often debates the extent to which different catalytic mechanisms are influenced by charge transfer (also known as hot electrons), plasmon induced resonant energy transfer, or thermal effects, in this study we do not attempt to disentangle potential contribution from these mechanisms. However, it is likely that the light activates the plasmonically active TiN nanoparticles and simply induces local collective heating at the microscale that results in the desorption of CO2. 10 mW/cm 2 320 mW/cm The conversion between ppm of CO2 to mmol CO2/g PEI can be found in Section S6. For these experiments, the same TiN-impregnated contactor system was used.