Significant progress has been made in direct air capture (DAC) in recent years. Evidence suggests that the large-scale deployment of DAC by adsorption would be technically feasible for gigatons of CO₂ capture annually. However, great efforts in adsorption-based DAC technologies are still required. This review provides an exhaustive description of materials development, adsorbent shaping, in situ characterization, adsorption mechanism simulation, process design, system integration, and techno-economic analysis of adsorption-based DAC over the past five years; and in terms of adsorbent development, affordable DAC adsorbents such as amine-containing porous materials with large CO₂ adsorption capacities, fast kinetics, high selectivity, and long-term stability under ultra-low CO₂ concentration and humid conditions. It is also critically important to develop efficient DAC adsorptive processes. Research and development in structured adsorbents that operate at low-temperature with excellent CO₂ adsorption capacities and kinetics, novel gas–solid contactors with low heat and mass transfer resistances, and energy-efficient regeneration methods using heat, vacuum, and steam purge is needed to commercialize adsorption-based DAC. The synergy between DAC and carbon capture technologies for point sources can help in mitigating climate change effects in the long-term. Further investigations into DAC applications in the aviation, agriculture, energy, and chemical industries are required as well. This work benefits researchers concerned about global energy and environmental issues, and delivers perspective views for further deployment of negative-emission technologies.

The search for efficient amine-functionalized materials for direct air capture (DAC) of CO₂ is highly important to achieve negative emissions. Here we report a new family of class 1 adsorbents for DAC by loading 67 wt% branched poly(ethylenimine) (PEI) onto Mg–Al–CO₃ layered double hydroxide-derived mixed metal oxides (MMOs), which exhibit unexpectedly large CO₂ uptakes (2.27 mmol g⁻¹), fast kinetics (1.1 mmol g⁻¹ h⁻¹), and high stability over 20 cycles at 25 °C under 0.4 mbar CO₂. The prepared MMO nanosheets are self-assembled into spherical shaped particles with abundant slit-like mesopores and broad pore size distribution. This ideal nanostructure leads to the uniform distribution of the impregnated PEIs and optimal accessibility for CO₂ molecules. The defect-abundant MMO layers provide strong electrostatic attraction to the attached polyamines, making the hybrid adsorbents thermally robust up to 300 °C. Enhanced capacity and stability are observed in the presence of moisture, thus facilitating the use of steam stripping to concentrate the desorbed CO₂.

This paper reviews recent advances in the shaping adsorbents: alternative geometric forms, key metrics for evaluation, typical steps of main shaping techniques, etc. , are discussed, which can serve as a reference for structured adsorbent design.

Extracting water from the air using a metal–organic framework (MOF) is an emerging solution to mitigate the global water crisis. Reported MOF water harvesters have improved water productivity from 0.1, 1.0 to 3.5 L H₂O kg_MOF ⁻¹ d⁻¹ using different strategies, but still cannot meet practical demands. Herein, we report the design of a MOF water harvester with tunable sorption–desorption behaviors by introducing cooling-assisted adsorption. Triple benefits brought by cooling effects—rapid sorption, enhanced capacity and reduced desorption temperature—deliver extraordinary productivities of 7.75–22.81 L H₂O kg_MOF ⁻¹ d⁻¹ in a diverse range of climates (10–35 °C, 20–80%RH), outperforming the best-performing MOF water harvester. Field tests produced 990.4 mL of clean water continuously throughout the day using a heat pump-integrated harvester in weather with an extremely low RH of 26%, corresponding to a productivity of 9.9 L H₂O kg_MOF ⁻¹ d⁻¹ with an energy consumption of 2.96 kW h L H₂O ⁻¹, demonstrating the great potential to provide adequate drinking water in real-world scenarios.