Structural-coupling driven cobalt metalloporphyrin⊂MIL-101(Fe) hybrids for efficient photocatalytic CO₂ reduction

Enhancing the photocatalytic CO₂ conversion efficiency of metal-organic frameworks (MOFs) remain a central challenge in advancing carbon capture and utilization (CCU) technologies. Herein, we report a mixed-ligand strategy to construct a hybrid MOF (denoted as CTN ⊂ NM) by incorporating a Co-metalated tetrakis(4-carboxyphenyl)porphyrin (CoTCPPNa₄, CTN) into an amine-functionalized MIL-101(Fe) framework (NH₂-MIL-101(Fe), abbreviated as NM; MIL = Materials of Institute Lavoisier, a prototypical series of robust MOFs). The optimized catalyst with a Co/Fe molar ratio of 0.40 achieves a HCOOH production rate of 119.11 μmol g^-1 h^-1 under visible light in the absence of a sacrificial agent, representing a 4.2-fold increase compared with pristine NM. When a sacrificial electron donor is introduced, the rate further rises to 179.87 μmol g^-1 h^-1. The markedly enhanced activity originates from the synergistic integration of CTN and NM: CTN provides strong visible-light absorption and efficient catalytic sites, while NM offers high porosity and strong CO₂ affinity. This cooperation broadens the light-absorption range, suppresses charge-carrier recombination, and accelerates CO₂-reduction kinetics. In addition, the Co³⁺ center in the metalloporphyrin macrocycle functions as an active CO₂ adsorption site, facilitating its activation and selective conversion to HCOOH. Overall, this study presents an effective mixed-ligand hybridization approach for solar-to-chemical energy conversion and provides valuable insights for the rational design of MOF-based photocatalysts toward carbon-neutral fuel production.