Carbon geological utilization and sequestration form a critical part of carbon capture, utilization, and storage (CCUS) technologies, and are widely viewed as a viable strategy for mitigating climate change and reducing atmospheric CO₂ levels [[1], [2], [3], [4], [5]]. The broader implementation of this approach relies heavily on both efficient resource use and secure long-term sequestration, particularly over periods lasting a century or more, where exceptional standards of safety and reliability must be maintained [[4], [5], [6], [7]]. Currently, onshore geological sequestration is mainly achieved through two technical routes. The first involves synergistic technologies that pair CO₂ enhanced oil recovery (EOR) with sequestration, while the second uses an integrated method combining CO₂ fracturing, displacement, and sequestration [8]. Deep low-permeability reservoirs tend to be tight formations, usually with porosity below 10 % and permeability under 0.1 mD. These reservoirs commonly exist in high-temperature conditions exceeding 130 °C, with formation water salinity levels that can surpass 105 mg/L, in addition to other extreme factors such as high shear stress. Such challenging conditions impose strict requirements on the performance durability of functional materials and the operational stability of CO₂ adaptive systems. Conventional materials often underperform in these settings, due to shortcomings such as limited temperature and salt resistance, weak acid tolerance, low CO₂ affinity, and insufficient long-term stability. In response to these challenges, CO₂ adaptive systems have gained increasing research attention for their dual role in enabling carbon emission reduction and supporting efficient resource development [[8], [9], [10]]. Current innovations in this field primarily include four types of technologies, including CO₂ responsive smart gels, CO₂ adaptive foam systems, self-adaptive nanobubble dispersion systems, and supercritical CO₂ thickeners [[11], [12], [13]]. This review will systematically elucidate the molecular design principles, functional mechanisms, and engineering applications of each these four adaptive material systems, with the aim of providing strategic insights for advancing CO₂ geological utilization and sequestration. (Fig. 1) These systems display high CO₂ affinity and strong environmental adaptability, showing considerable promise not only in enhancing oil recovery with integrated sequestration, CO₂ fracturing, and mobility control, but also in enabling large-scale, long-term CO₂ geological sequestration. With continued technological advancement, CO₂ adaptive systems are poised to play a key role in supporting the achievement of carbon neutrality goals throughout this century [[14], [15], [16]].

However, in the context of deep geological CO₂ utilization and sequestration, gel materials face severe challenges due to harsh conditions including high temperature, high salinity, and acidic CO₂ environments [17]. First generation gels primarily rely on the protonation of alkaline groups such as amines and amidines, whereas second-generation gels utilize frustrated Lewis pair (FLP)-mediated molecular bridging to achieve [[18], [19], [20]]. We propose that developing multi-network and multi-responsive systems based on polymer chain design and modulation principles can markedly enhance gel tolerance. Incorporating rigid chain segments helps maintain st0ructural integrity and chemical inertness under extreme conditions, while flexible segments provide dynamic adaptability and energy dissipation. The synergy between these components is essential for performance enhancement. It is particularly promising to integrate temperature- and salt-responsiveness with CO₂ sensitivity, enabling the design of environmentally adaptive CO₂ intelligent systems. Therefore, molecular design strategies for CO₂ stimuli responsive gels should emphasize precise regulation of synergistic effects among functional components to expand their potential for carbon sequestration in complex reservoir environments [21].

Progress in CO₂ foam performance relies on integrating interfacial strengthening, rheological control, and dynamic stability. Gaining deeper insight into structure–function relationships between nanomaterials and CO₂ foams, along with optimizing interactions among surfactants and polymers, offers promising pathways to enhance the long-term stability and environmental adaptability of CO₂ foams under complex geological conditions [22]. CO₂ nanobubbles exhibit exceptional mass-transfer efficiency and unique energy characteristics. In addition to accelerating carbonation kinetics, these nanobubbles facilitate the dissolution of mineral components in reservoir rocks, releasing cations such as calcium and magnesium. These ions subsequently combine with carbonate species to form valuable precipitates, including calcium carbonate and magnesium carbonate, which significantly improve both the efficiency and long-term security of CO₂ sequestration. The strong compatibility between CO₂ nanobubbles and CO₂-adaptive materials establishes this combination as a highly promising research direction in colloid and interface science. Key scientific challenges that need to be addressed to advance large-scale geological CO₂ utilization and ensure long-term sequestration include enhancing the durability of CO₂ nanobubbles in demanding interfacial environments, fully utilizing the responsive characteristics and high tolerance to temperature and salinity of CO₂-adaptive materials, and clarifying the reaction mechanisms through which reactive free radicals generated during nanobubble collapse interact with CO₂ to produce novel reactive species.

CO₂ fracturing improves reservoir stimulation by lowering rock-breaking pressure, expanding fractures, maintaining flow channels, and enhancing flowback. Techniques include dry fracturing, supercritical fracturing, and energy-enhanced fracturing [23,24]. In this system, VES forms a temperature- and CO₂ responsive reversible network. CO₂ thickeners work with perfluorinated surfactants to create a high-performance foam fracturing fluid. Nano-mineralization enables in-situ CO₂ stabilization and long-term sequestration. Key breakthroughs include: stable fluid viscosity under high-temperature and high-shear conditions; significantly reduced interfacial tension via optimized CO₂-adaptive foams for efficient flowback; and accelerated sequestration reactions through nano-mineralization. Current research focuses on VES resistant to 150 °C, molecular optimization of CO₂ thickeners, and digital monitoring of sequestration. As carbon neutrality advances, this system is expected to redefine unconventional resource development, offering a low-carbon, multifunctional model for the oil and gas industry's green transition.

CO₂ geological utilization and sequestration will rely on adaptive materials like CO₂ responsive gels, foams, nanobubbles, and thickeners to integrate energy development, resource use, and carbon management. These technologies will support global carbon neutrality strategies [25]. To address high-temperature and high-salinity reservoirs, there is a need to develop robust CO₂-responsive materials and advanced nanobubble-based extraction and sequestration methods. Establishing an integrated engineering approach combining fracturing [26], displacement, and sequestration will enhance synergies between oil production and carbon storage. Ensuring long-term sequestration safety requires improved monitoring and control of chemical and geomechanical behaviors. Integrating CCUS with hydrogen, geothermal, and other low-carbon energy systems is key to systemic decarbonization. Through multidisciplinary collaboration and system optimization, CCUS will drive the energy sector toward a carbon neutral future.