Microporous and hydrophobic polymers were synthesized and tested as NO oxidation catalysts to overcome water co-adsorption in combustion flue gas streams. The self-cross-linked 4,4'-bis(chloromethyl)-1,1'-biphenyl polymer (PBCMBP), with micropore volume of 0.38 cm(3)/g and surface area of 1430 m(2)/g, provided 62% NO oxidation efficiency at 25 degrees C in dry conditions but its performance dropped to 50% in the presence of 1.6 vol% moisture (wet conditions). To decrease performance loss, PBCMBP was modified with benzene (PBCMBP-BZ) to remove pendant chloromethyl groups, improving resistance to surface reactions with NO2 that add hydrophilicity. In wet conditions, PBCMBP-BZ has 59% NO oxidation efficiency, an 18% increase compared to PBCMBP at 25 degrees C. PBCMBP was also functionalized with dimethylamine (PBCMBP-DMA) to increase surface basicity, increasing NO oxidation by 11% in dry conditions, but decreasing NO oxidation in wet conditions by 30% due to increased proclivity to react with NO2. The combined impact of temperature and humidity was measured up to 100 degrees C, showing that moisture's impact decreases with increasing temperature and that PBCMBP-DMA outperforms other catalysts at higher temperatures. Findings suggest that catalyst surface chemistry can be manipulated to further improve NO oxidation performance, especially in the presence of moisture.