Enhancing CO2 photocatalytic reduction with a novel polymer catalyst: inducing reactive C–N bond formation through altered thermodynamic trends and exploring reduction kinetics

Abstract

Melamine–resorcinol–formaldehyde (M) is an innovative and promising carbon-based photocatalyst that enables the selective reduction of CO₂ to CH₃OH in line with green development principles. However, its formation mechanism is poorly understood, and hence, the process for improving mass/energy transfer in the reaction is limited. Herein, an efficient, environmentally friendly, and cost-effective strategy is developed for modifying M with Na₂CO₃ (X NaM, where X represents the mass of Na₂CO₃) to construct a mass/energy transfer-enhanced catalytic system with abundant exposed amine groups. Consequently, an impressive CH₃OH yield of 10.11 μmol g⁻¹ h⁻¹ was achieved without using any hole scavengers or precious metals. This demonstrates exceptional CH₃OH activity in the realm of non-metallic catalysts. The high activity is attributed to the involvement of Na₂CO₃ as a structure-directing template in regulating the thermodynamic bonding trends during catalyst polymerization, thereby inducing the formation of reactive C–N bonds and effectively enhancing the mass and energy transfer processes. Additionally, this work clarifies the reaction pathway for CO₂ reduction through in situ experimental investigations and density functional theory calculations. The unique hydrophilic–hydrophobic transition significantly enhances the adsorption capacity of CO₂ and proton utilization, thereby greatly improving catalytic activity. This work provides a paradigm for the molecular-level design of novel and efficient photocatalytic polymer semiconductors.