Developing　photocatalytic　coatings　onto　cementitious　materials　is　an　attractive　approach　to　combat　air　pollution.　However,　the　low　photocatalysis　durability　of　the　photocatalytic　cementitious　materials　is　the　main　challenge　for　their　large-scale　implementation　in　aggressive　outdoor　environments.　Here,　a　coating　composed　of　poly　hepta-zine　imides　(PHI)　was　applied　onto　hardened　cement　pastes　with　different　substrate　roughness　for　nitrogen　oxides　(NOx)　abatement　under　artificial　washing　and　natural　weathering.　The　apparent　appearance,　micro　-morphology　and　chemical　composition　of　the　PHI-coated　cement　pastes　were　characterized　via　visual　inspection,　scanning　electron　microscopy　equipped　with　energy-dispersive　X-ray　spectroscopy　and　attenuated　total　reflec-tance-Fourier　transform　infrared　analysis.　It　was　found　that　increasing　the　substrate　roughness　improved　the　adhesion　of　PHI　coating　against　the　washing　test,　contributing　to　a　higher　photocatalytic　efficiency　of　NOx　removal　at　highly　rough　substrates　after　subjecting　to　the　washing　test.　After　the　weathering　tests,　the　NOx　removal　of　PHI-coated　cement　pastes　increased　and　then　decreased　slightly　with　the　increasing　substrate　roughness;　the　highest　photocatalytic　efficiency　was　observed　at　a　substrate　roughness　of　2.83　mu　m.　The　obser-vations　open　a　window　for　improving　the　durability　of　photocatalytic　coatings　applied　onto　cementitious　ma-terials　under　real-life　conditions.