The world is currently facing a serious carbon emission problem, and the construction industry is one of the major emission sources. The development of efficient and low-cost catalytic technologies for CO₂ reduction has become the key to promote the transition to low-carbon buildings. Carbon nitride has received widespread attention due to its tunable energy band structure and environmental friendliness, and the combined modification strategy of copper modification and phosphorus doping is expected to significantly improve its photocatalytic efficiency. In this paper, we explore the potential of copper-modified phosphorus-doped polymerized carbon nitride (CMPDPCN) materials based on its application in photocatalytic CO₂ reduction and roof photovoltaic carbon-reduction systems in housing construction. In the study, firstly, block PCN, normal PCN, VAEPCN and CMPDPCN were prepared and their optical properties were analyzed by UV-vis spectroscopy and photoluminescence spectroscopy. Comparative CO₂ photodegradation tests were conducted using porous cement composite catalyst samples, and the results showed that the CO₂ degradation rate of the CMPDPCN sample reached 75.64% after 120 min of light exposure, which was much higher than that of the VAEPCN sample at 28.20%. Further roof photovoltaic simulations showed that the CMPDPCN module could enhance the power generation to 38.75 MW-h and the CO₂ degradation rate to 53.84% under 100m² condition. The above results indicate that copper-modified phosphorus-doped carbon nitride has significant application advantages in low-carbon buildings.
