Molecular Compartments Created in Metal-Organic Frameworks for Efficient Visible-Light-Driven CO₂ Overall Conversion

We report the construction of molecular compartments by the growth of narrow-band semiconductor nanoparticles, tungsten oxide and its hydrate, in the mesopores of a metal-organic framework (MOF), MIL-100-Fe. The location of these nanoparticles in pores and their spatial arrangement across the MOF crystal are unveiled by powder X-ray diffraction and small-angle neutron scattering, respectively. Such a composition with pore-level precision leads to efficient overall conversion of gas-phase CO₂ and H₂O to CO, CH₄, and H₂O₂ under visible light. When WO₃·H₂O nanoparticles are positioned in 2.5 nm mesopores with 24 wt %, the resulting composite, namely, 24%-WO₃·H₂O-in-MIL-100-Fe, exhibits a CO₂ reduction rate of 0.49 mmol·g^-1·h^-1 beyond 420 nm and an apparent quantum efficiency of 1.5% at 420 nm. These performances stand as new benchmarks for visible-light-driven CO₂ overall conversion. In addition to the size and location of semiconductor nanoparticles, the coordinated water species in the crystal are found critical for high catalytic activity, an aspect usually overlooked.