Tailoring the nanoscale morphology of calcium silicate hydrate for low-cost direct air carbon capture and storage.

The greenhouse effect, which affects ecosystems, weather patterns, and global temperatures, has been exacerbated by the increase in air concentrations resulting from the expansion. Direct air capture is a critical component of the strategy to combat climate change and is also essential for carbon capture, utilization, and storage, however, they are currently prohibitively expensive for practical applications, which underscores the necessity of selecting a low-cost material that has exceptional carbon capture efficacy. Considering their straightforward and economical production processes, cementitious materials are recognized as potential candidates. While existing research has established fundamental relationships between Ca/Si ratios (0.8-1.8) and carbonation kinetics under varying humidity (30-70 % RH), critical knowledge gaps persist regarding nanoscale morphological engineering of calcium silicate hydrate (C-S-H) through self-assembly processes. Specifically, the effects of pore architecture modulation and crystallographic orientation control on CO sequestration efficiency remain underexplored, hindering the optimization of sorbent carbonation rate and long-term structural stability. This study addresses these limitations through systematic investigation of morphology-dependent carbonation pathways, providing new insights for designing next-generation carbon-negative cementitious composites." Through morphology-controlled synthesis, five distinct C-S-H nanostructures were engineered: flower-like (F), cuboid-like (C), bulk-like (B), hybrid (H), and rod-like (R) configurations. Systematic evaluation under real-world direct air capture conditions (300 ppm CO) revealed morphology-dependent performance gradients. Rod-like architectures demonstrated superior CO uptake capacity (9.93 ± 0.03 mmol·g). Economic analysis showed production costs for rod-like C-S-H reached as low as 29.7 % of commercial DAC materials. This morphology-dependent enhancement, positions rod-like C-S-H as a viable candidate for scalable carbon capture, utilization, and storage (CCUS) system integration.