Recent progress in indoor CO2 capture for urban decarbonization

Developing green buildings with high indoor air quality (IAQ) and low energy consumption is essential for urban decarbonization. However, achieving this objective remains challenging because maintaining high IAQ requires frequent ventilation for the timely removal of human-exhaled carbon dioxide (CO2), inevitably resulting in substantial air-conditioning energy demand. One emerging solution is indoor CO2 capture (ICC) technology comprising a CO2 capture device and a heating, ventilation and air-conditioning system to directly capture indoor CO2 and recirculate the treated CO2-lean air to minimize the demand for ventilation. In this Review, we describe the recent progress in leveraging ICC technology to achieve CO2 removal, high IAQ and energy savings in urban buildings. We provide an overview of the fundamental working principles of representative ICC methods and summarize the strategies that can enhance the capture capacity and moisture tolerance of ICC systems for improved indoor adaptability. Furthermore, we describe the energy-saving potential of ICC and its correlation with city climates. Finally, we identify the remaining technical, political and social challenges and provide future directions to promote the widespread implementation of ICC technologies to fortify the climate resilience and sustainability of cities. This Review makes the case for enhancing indoor air quality through indoor CO2 capture and describes how technological advances in materials and chemistry enabled these improvements. New constructions or retrofitting buildings would allow these advances to be implemented to improve CO2 capture.