Tailoring Photocatalytic Activity in Porphyrin-MOFs: The Role of Amine-Functional 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-orginic 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 -COOH group act as H2O adsorption sites. The amine functionality synergistically enhances CO2 adsorption affinity. 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.