Tailoring photocatalytic activity in porphyrin-MOFs: the role of amino-functionalized pillars in CO2 adsorption and band structure modulation

Abstract

The urgent need for sustainable carbon capture and conversion technologies has driven the development of advanced photocatalytic materials. Cobalt-porphyrin metal–organic frameworks (MOFs), engineered with tailored pore sizes, Lewis-basic functional groups, and optimized catalytic site densities, exhibit enhanced CO₂ adsorption capacity while facilitating efficient light harvesting and charge separation. Herein, we report two cobalt-based pillared-layer porphyrinic MOFs (TCPP-Pyz-Co and TCPP-NH₂Pyz-Co) designed for efficient CO₂ photoreduction. By incorporating amino-functionalized pillars, TCPP-NH₂Pyz-Co demonstrates a high CO₂ adsorption capacity of 82.8 cm³ g⁻¹ at 273 K. Furthermore, the introduced NH₂ groups narrow the bandgap and improve charge separation efficiency. As a result, TCPP-NH₂Pyz-Co achieves a remarkable CO production rate of 2221.4 μmol g⁻¹ h⁻¹, surpassing that of TCPP-Pyz-Co (1807.6 μmol g⁻¹ h⁻¹). Density functional theory (DFT) calculations reveal that the Co–Co paddlewheel nodes serve as the primary CO₂ adsorption sites, while the –COO group acts as an H₂O adsorption site. The amino functionality synergistically enhances CO₂ adsorption affinity due to the secondary sites in a position near to the primary CO₂ adsorption sites. This work underscores the pivotal role of Lewis-base functionalization in optimizing MOFs for dual CO₂ capture and conversion, providing a blueprint for next-generation photocatalysts.