This week’s publication highlights relate to direct air capture, forestation and marine carbon removal.
Epoxide-Modified Diethylenetriamine for Ambient-Temperature Direct Air Capture
Abstract
Small amine-based direct air capture materials show promising CO2 capture performance but suffer stability issues─evaporation losses, oxidative degradation, CO2-induced urea formation, and moisture-driven leaching─exacerbated by energy-intensive thermal regeneration (80–120 °C). Here, we employed controlled epoxide functionalization of the small amine diethylenetriamine (DETA) to mitigate its stability issues while enabling reversible CO2 binding and energy-efficient desorption at ambient temperature. Modification with 1,2-epoxybutane across stoichiometric ratios (1:1 to 1:2) produces materials with tailored molecular weights and intermolecular interactions, leading to enhanced thermal stability by suppressing evaporative losses observed in unmodified DETA and markedly improved oxidative resistance. Despite the increased molecular weight compared to DETA, the functionalized DETA molecules exhibit fast CO2 adsorption rates of 1.03–1.28 mmol/g/h, while achieving rapid CO2 desorption at ambient temperatures and 66% regeneration within 1 h at 30 °C. The optimized material retains 97.8% capacity after 24 h of oxidative stress testing (60 °C in air), while DETA cannot be properly evaluated due to evaporation during thermal treatment. Real-world validation using ambient atmospheric air demonstrates stable cycling performance over 50 consecutive adsorption–desorption cycles, featuring ambient-temperature regeneration and minimal capacity loss. This facile and effective modification approach using 1,2-epoxybutane to (i) increase the molecular weight of small amines (thus minimizing evaporative loss) and (ii) generate a high fraction of sterically hindered secondary amines for improved oxidative resistance may facilitate the scalable production of small amine-based materials for CO2 capture applications.
Friedman, K. and Yu, M. (2026) Epoxide-Modified Diethylenetriamine for Ambient-Temperature Direct Air Capture 18 (2) ACS Applied Materials & Interfaces.
Read the full paper here: Epoxide-Modified Diethylenetriamine for Ambient-Temperature Direct Air Capture I ACS Applied Materials & Interfaces.
Quantifying Uncertainty for Near-Natural Forestation in Arid Regions
Abstract
Forestation plays a pivotal role in arid regions to mitigate climate change and land degradation. However, conventional tree planting initiatives frequently fail to emulate the ecological services provided by natural forests, and may threaten natural environments. Here, we integrated Variational Inference into a one-dimensional convolutional neural network (1DCNN) to facilitate near-natural forestation planning with uncertainty quantification in arid regions. The model was compared with machine learning approaches and exemplarily applied in the lower Tarim River Basin (LTRB), which is one of the largest inland basins around the world and has carried out long-term restoration actions. The results demonstrated that: 1) The Variational 1DCNN outperformed conventional models by up to 13.1 % in accuracy, and avoiding the overestimation of the forestation area (106–142 %) observed in traditional approaches. 2) The locations of potential afforestation areas with low uncertainty in LTRB are highly consistent with the actual situation and are primarily distributed near river channels. 3) Hydrological and topographical factors exerted a great influence on the uncertainty in potential forestation simulations. The near-natural forestation model developed here exhibits satisfactory performance in forestation opportunity prediction, and uncertainty quantification can enhance sustainable forestation planning in arid regions.
Qu, L. et al. (2026) Quantifying Uncertainty for Near-Natural Forestation in Arid Regions 223 (105553) Journal of Arid Environments.
Read the full paper here: Quantifying Uncertainty for Near-Natural Forestation in Arid Regions I Journal of Arid Environments.
A Comprehensive Review of Metal-Organic Frameworks (MOFs) Applications as Sorbents and Membranes for Carbon Capture through Direct Air Capture (DAC) Technology
Abstract
The continued reliance on fossil fuels has significantly increased greenhouse gas (GHG) emissions, particularly carbon dioxide (CO2), thus accelerating global warming. Direct air capture (DAC) has emerged as a promising negative emission technology capable of extracting CO2 directly from ultra-dilute atmospheric concentrations. Unlike point-source capture, DAC offers the advantage of deployment location flexibility and global scalability; however, its effectiveness depends on the development of advanced sorbent materials with high CO2 selectivity, low regeneration energy requirements, and long-term stability under realistic operating conditions. Metal–organic frameworks (MOFs), an emerging class of porous crystalline materials, have attracted a significant interest for DAC applications due to their tunable porosity, chemical versatility, and potential for functionalization.
This study critically evaluates state-of-the-art MOFs, including pure frameworks, amine-functionalized, hybrid ultra-microporous materials, and MOF-based membranes, by comparing their performances under DAC-relevant conditions and identifying the most promising candidates. Beyond reviewing the material key performance indicators (KPIs), the review assesses key technical, economic, and environmental barriers that currently hinder large-scale deployment of MOF-based DAC technologies. Challenges such as energy-intensive synthesis routes, material costs, structural deformation under moisture, and integration into process configurations are discussed. In addition, design strategies, including scalable and low-cost synthesis methods, surface functionalization for improved CO2 binding, and innovative regeneration schemes, are highlighted as potential solutions. By critically evaluating and integrating recent advances and outlining future research pathways, this work aims to provide a comprehensive framework for accelerating the implementation of MOF-based DAC systems within carbon-negative technologies.
Nikkhah, S. et al. (2026) A Comprehensive Review of Metal-Organic Frameworks (MOFs) Applications as Sorbents and Membranes for Carbon Capture through Direct Air Capture (DAC) Technology 416 (137999) Fuel.
Read the full paper here: A Comprehensive Review of Metal-Organic Frameworks (MOFs) Applications as Sorbents and Membranes for Carbon Capture through Direct Air Capture (DAC) Technology I Fuel.
Efficacy of Individual and Combined Terrestrial and Marine Carbon Dioxide Removal
Abstract
Limiting global temperature rise below 2 °C requires significant reduction in greenhouse gas emissions and large-scale carbon dioxide removal (CDR). This study assesses the CO2 sequestration and efficacy of two CDR approaches, bioenergy with carbon capture and storage (BECCS) and ocean alkalinity enhancement (OAE), applied individually and in combination. Using the Norwegian Earth System Model, simulations were designed to ramp up deployment of BECCS and OAE, to an additional area of 5.2 million km2 by 2100 for bioenergy feedstock for BECCS, and a CaO deployment rate of approximately 2.7 Gt yr−1 for OAE within the exclusive economic zones of Europe, the United States and China. The combined land–ocean CDR simulation revealed a largely additive carbon removal effect. Over 2030−2100, OAE sequestered 7 ppm of CO2 with an accumulated 82.3 Gt CaO, achieving a CDR effectiveness of 0.08 ppm (∼0.17 PgC) per Gt CaO, while BECCS reduced 16 ppm of CO2, with CDR effectiveness of 3.1 ppm per million km2 of bioenergy crops. Together, the carbon removal achieved by BECCS and OAE corresponds to anthropogenic CO2 emissions of 5.4 Gt CO2 yr−1 by 2100, slightly more than 60% of current global transport sector emissions. Notably, the efficiency of BECCS and OAE alone was unaffected by their concurrent deployment. Nevertheless, simulations revealed distinct non-linear interactions, such as declines in land and soil carbon sinks in the combined scenario. Furthermore, all simulations show negligible effects on the global annual mean temperature. These results highlight near-additive CDR responses even under net-negative emissions, but feedback on land and ocean carbon sinks must be considered when designing CDR portfolios. This study provides new insights into CDR portfolio design and Earth system feedback under an overshoot scenario, highlighting both their potential and the need for continued emissions cuts and supportive policies.
Sathyanadh, A. et al. (2026) Efficacy of Individual and Combined Terrestrial and Marine Carbon Dioxide Removal 21 (014032) Environmental Research Letters.
Read the full paper here: Efficacy of Individual and Combined Terrestrial and Marine Carbon Dioxide Removal I Environmental Research Letters.
Simulated Earth System Response to Acid Downwelling as a Form of Ocean Alkalinity Enhancement
Abstract
‘Acid downwelling’ (AD) is a proposed marine carbon dioxide removal (CDR) method, which describes the idea of electrochemically splitting open ocean surface water into an alkaline solution to remain at the surface ocean and cause additional ocean CO2 uptake, and into an acidic solution that is pumped down into the deep ocean for disposal via vertical pipes. In this study, we simulate idealized large-scale AD in an Earth system model of intermediate complexity with different acid injection depths and downwelling intensities and find a maximum marine CDR (mCDR) potential for continuous AD (0.25 Pmol yr−1) of 320 Pg C until the end of the millennium under an extended RCP 4.5 CO2 emissions scenario. However, the acidity temporarily stored at depth resurfaces primarily around the Southern Ocean via ocean circulation and causes regional CO2 outgassing. Furthermore, too intense downwelling of warm surface water leads to an increase in ocean interior temperatures causing further Earth system feedbacks and accelerates the re-emergence of downwelled acidity to the surface. However, the extent to which this re-emergence causes CO2 outgassing into the atmosphere is emissions scenario dependent. This study highlights that large-scale ocean circulation, the investigated time frame, and the future CO2 emission scenario all need to be considered in order to determine the mCDR potential of AD.
Tiwary, E. et al. (2026) Simulated Earth System Response to Acid Downwelling as a Form of Ocean Alkalinity Enhancement 21 (014019) Environmental Research Letters.
Read the full paper here: Simulated Earth System Response to Acid Downwelling as a Form of Ocean Alkalinity Enhancement I Environmental Research Letters.