An official website of the United States government
Abstract Marine carbon dioxide removal (mCDR) is gaining interest as a tool to meet global climate goals. Because the response of the ocean–atmosphere system to mCDR takes years to centuries, modeling is required to assess the impact of mCDR on atmospheric CO2reduction. Here, we use a coupled ocean–atmosphere model to quantify the atmospheric CO2reduction in response to a CDR perturbation. We define two metrics to characterize the atmospheric CO2response to both instantaneous ocean alkalinity enhancement (OAE) and direct air capture (DAC): the cumulative additionality (α) measures the reduction in atmospheric CO2relative to the magnitude of the CDR perturbation, while the relative efficiency (ϵ) quantifies the cumulative additionality of mCDR relative to that of DAC. For DAC,αis 100% immediately following CDR deployment, but declines to roughly 50% by 100 years post-deployment as the ocean degasses CO2in response to the removal of carbon from the atmosphere. For instantaneous OAE,αis zero initially and reaches a maximum of 40%–90% several years to decades later, depending on regional CO2equilibration rates and ocean circulation processes. The global meanϵapproaches 100% after 40 years, showing that instantaneous OAE is nearly as effective as DAC after several decades. However, there are significant geographic variations, withϵapproaching 100% most rapidly in the low latitudes whileϵstays well under 100% for decades to centuries near deep and intermediate water formation sites. These metrics provide a quantitative framework for evaluating sequestration timescales and carbon market valuation that can be applied to any mCDR strategy.
more »
« less
Challenges and Opportunities: Metal–Organic Frameworks for Direct Air Capture
Abstract Global reliance on fossil fuel combustion for energy production has contributed to the rising concentration of atmospheric CO2, creating significant global climate challenges. In this regard, direct air capture (DAC) of CO2from the atmosphere has emerged as one of the most promising strategies to counteract the harmful effects on the environment, and the further development and commercialization of this technology will play a pivotal role in achieving the goal of net‐zero emissions by 2050. Among various DAC adsorbents, metal–organic frameworks (MOFs) show great potential due to their high porosity and ability to reversibly adsorb CO2at low concentrations. However, the adsorption efficiency and cost‐effectiveness of these materials must be improved to be widely deployed as DAC sorbents. To that end, this perspective provides a critical discussion on several types of benchmark MOFs that have demonstrated high CO2capture capacities, including an assessment of their stability, CO2capture mechanism, capture‐release cycling behavior, and scale‐up synthesis. It then concludes by highlighting limitations that must be addressed for these MOFs to go from the research laboratory to implementation in DAC devices on a global scale so they can effectively mitigate climate change.
more »
« less
- Award ID(s):
- 2119433
- PAR ID:
- 10641340
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 34
- Issue:
- 43
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Carbon capture and sequestration (CCS) from industrial point sources and direct air capture are necessary to combat global climate change. A particular challenge faced by amine‐based sorbents—the current leading technology—is poor stability towards O2. Here, we demonstrate that CO2chemisorption in γ‐cylodextrin‐based metal–organic frameworks (CD‐MOFs) occurs via HCO3−formation at nucleophilic OH−sites within the framework pores, rather than via previously proposed pathways. The new framework KHCO3CD‐MOF possesses rapid and high‐capacity CO2uptake, good thermal, oxidative, and cycling stabilities, and selective CO2capture under mixed gas conditions. Because of its low cost and performance under realistic conditions, KHCO3CD‐MOF is a promising new platform for CCS. More broadly, our work demonstrates that the encapsulation of reactive OH−sites within a porous framework represents a potentially general strategy for the design of oxidation‐resistant adsorbents for CO2capture.more » « less
-
Escalating carbon dioxide (CO2) emissions have intensified the greenhouse effect, posing a significant long-term threat to environmental sustainability. Direct air capture (DAC) has emerged as a promising approach to achieving a net-zero carbon future, which offers several practical advantages, such as independence from specific CO2 emission sources, economic feasibility, flexible deployment, and minimal risk of CO2 leakage. The design and optimization of DAC sorbents are crucial for accelerating industrial adoption. Metal-organic frameworks (MOFs), with high structural order and tunable pore sizes, present an ideal solution for achieving strong guest-host interactions under trace CO2 conditions. This perspective highlights recent advancements in using MOFs for DAC, examines the molecular-level effects of water vapor on trace CO2 capture, reviews data-driven computational screening methods to develop a molecularly programmable MOF platform for identifying optimal DAC sorbents, and discusses scale-up and cost of MOFs for DAC.more » « less
-
CO2capture from post-combustion flue gas originating from coal or natural gas power plants, or even from the ambient atmosphere, is a promising strategy to reduce the atmospheric CO2concentration and achieve global decarbonization goals. However, the co-existence of water vapor in these sources presents a significant challenge, as water often competes with CO2for adsorption sites, thereby diminishing the performance of adsorbent materials. Selectively capturing CO2in the presence of moisture is a key goal, as there is a growing demand for materials capable of selectively adsorbing CO2under humid conditions. Among these, metal–organic frameworks (MOFs), a class of porous, highly tunable materials, have attracted extensive interest for gas capture, storage, and separation applications. The numerous combinations of secondary building units and organic linkers offer abundant opportunities for designing systems with enhanced CO2selectivity. Interestingly, some recent studies have demonstrated that interactions between water and CO2within the confined pore space of MOFs can enhance CO2uptake, flipping the traditionally detrimental role of moisture into a beneficial one. These findings introduce a new paradigm: water-enhanced CO2capture in MOFs. In this review, we summarize these recent discoveries, highlighting examples of MOFs that exhibit enhanced CO2adsorption under humid conditions compared to dry conditions. We discuss the underlying mechanisms, design strategies, and structural features that enable this behavior. Finally, we offer a brief perspective on future directions for MOF development in the context of water-enhanced CO2capture.more » « less
-
Abstract Capturing and sequestering carbon dioxide (CO2) from the atmosphere via large‐scale direct air capture (DAC) deployment is critical for achieving net‐zero emissions. Large‐scale DAC deployment, though, will require significant cost reductions in part through policy and investment support. This study evaluates the impact of policy interventions on DAC cost reduction by integrating energy system optimization and learning curve models. We examine how three policy instruments—incremental deployment, accelerated deployment, and R&D‐driven innovation—impact DAC learning investment, which is the total investment required until the technology achieves cost parity with conventional alternatives or target cost. Our findings show that while incremental deployment demands significant learning investment, R&D‐driven innovation is considerably cheaper at cost reduction. Under a baseline 8% learning rate, incremental deployment may require up to $998 billion to reduce costs from $1,154 to $400/tCO2, while accelerated deployment support could save approximately $7 billion on that investment. In contrast, R&D support achieves equivalent cost reductions at less than half the investment of incremental deployment. However, the effectiveness of R&D intervention varies with learning rates and R&D breakthroughs. R&D yields net benefits in all cases except at extremely low breakthroughs (5%) and very high learning rates (20%), where they are slightly more expensive. For learning rates below 20%, R&D provides net benefits even at minimal breakthroughs. These findings underscore the need for comprehensive public policy strategies that balance near‐term deployment incentives with long‐term innovation investments if we are to ensure DACS becomes a viable technology for mitigating climate change.more » « less
