Adsorbent
Support material
Capture
CO 2 capture
Energy
Advantages
Limitations
Lifetime
Durability
type
mechanism
capacity (mmol/g)
efficiency
and
stability
Amine-
Mesoporous Chemisorption
High capacity, low regeneration energy, good recyclability Enhanced amine dispersion, high uptake under humid conditions High CO₂ affinity, stable adsorption at ambient temperature Lower energy regeneration, good moisture
Oxidative degradation
Moderate, degradation over cycles
functionalised silica (PEI/TEPA on SBA-15) PEI on PME (Pore-expanded mesoporous
silica
(carbamate & bicarbonate)
2.0 – 4.5
Moderate
Moderate
at high
temperatures
Extra-large pore silica
Chemisorption (amine-CO₂) interaction)
Complex synthesis, higher cost
High, stable
3.5 – 7.3
High
under multiple High
cycles
silica)
TEPA on g -Al₂O₃
g -Al₂O₃
Strong
Lower
Moderate,
chemisorption (carbamate)
1.5 – 3.8
Moderate
adsorption under humid conditions Lower capacity compared to g -Al₂O₃ Moisture sensitivity,
good
Moderate
oxidation resistance
MOF-based adsorbents (MIL-101(Cr)
MOF (MIL- 101(Cr))
Weak
Moderate, sensitive to high humidity
chemisorption (carbamic acid)
1.2 – 3.5
Moderate
Moderate
-TEPA)
tolerance
Mg₂(dobpdc) functionalised with amine
MOF (Mg₂ (dobpdc))
Cooperative chemisorption
Moderate to high
High selectivity,
Moderate, dependent on humidity
4.0 – 6.8
tunable
Moderate
adsorption, excellent CO₂ uptake
high
regeneration energy required
UiO-66-NH₂
MOF
Chemisorption
High surface
Low CO₂ uptake, High, stable
(UiO-66)
& physisorption 2.1 – 4.2
Moderate
area, good thermal competitive
under humid conditions
High
stability
water
adsorption
ZIF-8
MOF (ZIF-8) Physisorption
Good moisture tolerance, Recyclability
Low CO₂ selectivity
functionalised with amine
and weak
1.5 – 3.0
High
Moderate
Moderate
chemisorption
Polymer-hybrid
MOF/polymer Chemisorption 3.0 – 5.5 composites & physisorption
High
Enhanced stability,
Potential complexity in synthesis, moisture sensitivity
High,
MOFs
dependent on polymer
High
tunable porosity, improved CO₂
type
uptake
MMO-supported Mixed metal Chemisorption 3.0 – 6.0
High
High capacity, regenerability,
Cost of material synthesis
amines
oxides (MMOs) Zeolites, activated carbons
High
High
scalable
Zeolites and carbon-based adsorbents
Physisorption
0.5 – 2.0
Very high
Low-cost materials,
Low selectivity, High for
sensitive to moisture
zeolites, lower for carbon
Moderate
stable structure
Table 1 Comparison of DAC adsorbents
modifications that enhance their resistance to moisture and maintain their adsorption efficiency. Looking ahead, the real breakthrough in DAC will likely come from better hybrid materials as sorbents that can be cheaply produced, highly durable, and ultra-efficient in CO₂ capture. Research is advancing rapidly, and what seems like an obstacle today could be solved within the next decade. Some of the most exciting developments include: • Combining amines with MMOs to improve stability while maintaining low-temperature regeneration. • Encapsulating MOFs with hydrophobic
polymers to make them moisture-resistant and more durable. • Exploring biomimetic materials that mimic natural carbon-fixing mechanisms, such as enzyme-based adsorption systems. The next challenge? Scaling up. DAC materials are only half the equation – turning lab-scale success into gigaton-scale carbon removal will require massive infrastructure investment, smart policy incentives, and an energy system that can power DAC without undoing its benefits. Challenges and future directions DAC has come a long way from conceptual technology to a real-world climate solution with
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