Atomically Dispersed High‐Density Al–N₄ Sites in Porous Carbon for Efficient Photodriven CO₂ Cycloaddition

Abstract

Highly active catalysts that can directly utilize renewable energy (e.g., solar energy) are desirable for CO2 value‐added processes. Herein, aiming at improving the efficiency of photodriven CO2 cycloaddition reactions, a catalyst composed of porous carbon nanosheets enriched with a high loading of atomically dispersed Al atoms (≈14.4 wt%, corresponding to an atomic percent of ≈7.3%) coordinated with N (AlN4 motif, Al–N–C catalyst) via a versatile molecule‐confined pyrolysis strategy is reported. The performance of the Al–N–C catalyst for catalytic CO2 cycloaddition under light irradiation (≈95% conversion, reaction rate = 3.52 mmol g−1 h−1) is significantly superior to that obtained under a thermal environment (≈57% conversion, reaction rate = 2.11 mmol g−1 h−1). Besides the efficient photothermal conversion induced by the carbon matrix, both experimental and theoretical analysis reveal that light irradiation favors the photogenerated electron transfer from the semiconductive Al–N–C catalyst to the epoxide reactant, facilitating the formation of a ring‐opened intermediate through the rate‐limiting step. This study not only provides an advanced Al–N–C catalyst for photodriven CO2 cycloaddition, but also furnishes new insight for the rational design of superior photocatalysts for diverse heterogeneous catalytic reactions in the future.

Emerging Ultrahigh‐Density Single‐Atom Catalysts for Versatile Heterogeneous Catalysis Applications: Redefinition, Recent Progress, and Challenges

“…The hollow porous structure can promote mass transport and improve photothermal efficiency; the atomiclevel-dispersed Zn-N 4 active sites can fully contact with CO 2 and epoxide molecules, improving photocatalytic CO 2 cycloaddition performances. Chen and co-workers [181] also reported a porous carbon nanosheet-supported high-loading single-atom Al (14.4 wt%) catalyst (Al-N 4 ) by a molecular-confined pyrolysis strategy to improve the photothermal efficiency of CO 2 cycloaddition reaction (95% conversion) under light irradiation.…”

“…The 3D carbon nanostructures (e.g., 3D carbon nanocages and 3D porous carbon nanosheets) exhibit high‐efficiency charge transfer, excellent photorefractive properties, and photothermal effects, which have attracted extensive attention in the field of photocatalysis in recent years. [ 177,181 ] The cyclic addition reaction of CO 2 and epoxides to form cyclic carbonates has 100% atomic economy in CO 2 green conversion, and its products are of great industrial value and broad application prospect. [ 182 ] Jiang and co‐workers reported N‐doped 3D carbon nanocages containing ultrahigh‐concentrated single‐atom Zn (11.3 wt%) from the high‐temperature pyrolysis of ZIF‐8 (rich in N and Zn elements), which has excellent photocatalytic properties (94% in conversion) for the addition reaction of CO 2 and epoxide under simulated sunlight irradiation at ambient temperature (see Figure 17L–N).…”

“…The hollow porous structure can promote mass transport and improve photothermal efficiency; the atomic‐level‐dispersed Zn–N 4 active sites can fully contact with CO 2 and epoxide molecules, improving photocatalytic CO 2 cycloaddition performances. Chen and co‐workers [ 181 ] also reported a porous carbon nanosheet‐supported high‐loading single‐atom Al (14.4 wt%) catalyst (Al–N 4 ) by a molecular‐confined pyrolysis strategy to improve the photothermal efficiency of CO 2 cycloaddition reaction (95% conversion) under light irradiation. The enhanced photothermal conversion induced by carbon (via lattice vibration [ 183 ] ) and the fast photogenerated electron transfer from the M–N 4 sites (via electron pump [ 147 ] ) conjointly facilitate the formation of ring‐opened intermediates and promote CO 2 cycloaddition reaction rates.…”

Greenery-inspired nanoengineering of bamboo-like hierarchical porous nanotubes with spatially organized bifunctionalities for synergistic photothermal catalytic CO2 fixation

“…4f). 69,70 When single Ni atoms adsorb and polarize the epoxides, the nucleophilic attack of the bromine ion in the HMPs-NH 2 on the less sterically hindered carbon atom in the epoxy compound results in a ring-opening process. The ring-opening intermediate was detected by GC-MS analysis in the presence of the obtained Ni-BNCNTs@HMPs-NH 2 and epoxides (Fig.…”

“…According to the literature, the semiconductive carbon networks can generate photogenerated electrons and promote the CO 2 cycloaddition reaction under light irradiation conditions. 68,69 The photogenerated electrons induced by the Ni-BNCNTs@HMPs-NH 2 under irradiation were studied using electron paramagnetic resonance (EPR) measurements (Fig. 4h).…”