Highly Efficient Photocatalytic CO2-to-CO on Ni-Based Cationic Polymer with TiO2-Assisted Exfoliation and Stabilization

Abstract

Porous organic polymers have shown great potential in photocatalytic CO₂ reduction due to their unique tunable structure favoring gas adsorption and metal sites integration. However, efficient photocatalysis in porous polymers is greatly limited by the low surface reactivity and electron mobility of bulk structure. Herein, we incorporate TiO₂ nanoparticles and Ni(II) sites into a layered cationic imidazolium polymer (IP), in which the imidazolium moieties and free anions can stabilize the key intermediates and enhance the reaction kinetics of CO₂ reduction. During the photocatalytic reaction, the layered TiO₂/NiIP is in situ exfoliated to nanosheets (NSs) with more accessible active sites and shorten electron transport pathways. The formed TiO₂/NiIP-NSs exhibit an impressively high CO production rate as 54.9 mmol ⋅ g⁻¹ ⋅ h⁻¹ with selectivity of 99.9 %. The embedding with TiO₂ nanoparticles could improve the electron transport efficiency so as to facilitate the photochemical stripping process of layered polymer. Moreover, the exfoliated nanosheets with assistance of TiO₂ possess excellent stability during the recycling experiments in comparison to the rapidly declined activity of NiIP-NSs. This work presents a new strategy to construct highly efficient photocatalysts for CO₂ reduction.