Solar concentrated-light driven direct air capture with fast desorption kinetics using amine-modified monolithic composites

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S1385894726070452

Authors: Fang Wang, Xuelin Xu, Zhonghai Zhang, Wendi Liu, Jinchi Mu, Jiandong Chen, Tao Wang 

22 July 2026

Highlights

•A concentrated-light driven monolithic PEI/Ni/γ-Al2O3 offers humidity tolerance and enhanced heat/mass transfer for DAC.

•DAC desorption completes in 2 min at 70 °C with desorption enthalpy of 45.9 kJ/mol, showing good regeneration performance.

•Humidity shifts CO2 capture from carbamate to bicarbonate, achieving 2.35 mmol/g uptake and stable cycling over 18 cycles.

Abstract

The practical deployment of direct air capture (DAC) is hindered by insufficient mass and heat transfer, along with high energy consumption during regeneration, which are intrinsic drawbacks of conventional powdered amine adsorbents. To mitigate these bottlenecks, this work constructs a concentrated-light driven DAC system using a monolithic PEI/Ni/γ-Al2O3 adsorbents. The monolithic architecture offers a combination of mechanical robustness, humidity tolerance, and enhanced mass and heat transport. The optimized monolith exhibits a CO2 adsorption capacity of 2.35 mmol/g from 420 ppm CO2 in air, with an amine efficiency of 0.31 mol CO2/mol amine and a regeneration efficiency of 96.92% ± 1.49%. Notably, concentrated light enables complete adsorbent desorption within 2 min at a moderate temperature of 70 °C, and the intrinsic CO2 desorption enthalpy is 45.9 kJ/mol. Moreover, in-situ FT-IR and DFT calculations reveal two distinct reaction mechanisms under dry and humid conditions, where humidity redirects the reaction pathway from the carbamate route to the stronger-bonded bicarbonate mechanism, driven by efficient electron transfer within water-mediated hydrogen-bonded networks. After 18 consecutive adsorption-desorption cycles, the PEI/Ni/γ-Al2O3 monolith maintains a steady CO2 capacity of 1.94 mmol/g, verifying its cycling stability. This study offers a promising strategy for concentrated-light driven DAC, which could provide insights for further development of negative carbon emission techniques.

Source: ScienceDirect