Molecular Dye-Sensitized Photocatalysis with Metal-Organic Framework and Metal Oxide Colloids for Fuel Production

Colloidal dye-sensitized photocatalysis is a promising route toward efficient solar fuel production by merging properties of catalysis, support, light absorption, and electron mediation in one. Metal-organic frameworks (MOFs) are host materials with modular building principles allowing scaffold property tailoring. Herein, we combine these two fields and compare porous Zr-based MOFs UiO-66-NH2(Zr) and UiO-66(Zr) to monoclinic ZrO2 as model colloid hosts with co-immobilized molecular carbon dioxide reduction photocatalyst fac-ReBr(CO)(3)(4,4 '-dcbpy) (dcbpy = dicarboxy-2,2 '-bipyridine) and photosensitizer Ru(bpy)(2)(5,5 '-dcbpy)Cl-2 (bpy = 2,2 '-bipyridine). These host-guest systems demonstrate selective CO2-to-CO reduction in acetonitrile in presence of an electron donor under visible light irradiation, with turnover numbers (TONs) increasing from ZrO2, to UiO-66, and to UiO-66-NH2 in turn. This is attributed to MOF hosts facilitating electron hopping and enhanced CO2 uptake due to their innate porosity. Both of these phenomena are pronounced for UiO-66-NH2(Zr), yielding TONs of 450 which are 2.5 times higher than under MOF-free homogeneous conditions, highlighting synergistic effects between supramolecular photosystem components in dye-sensitized MOFs.

Automated summary

Colloidal dye-sensitized photocatalysis combines properties of catalysis, support, light absorption, and electron mediation in efficient solar fuel production. Metal-organic frameworks (MOFs) can tailor properties for scaffold applications. Combining these fields, the host-guest systems demonstrate selective CO2-to-CO reduction with increasing turnover numbers attributed to enhanced electron hopping and CO2 uptake, particularly pronounced in UiO-66-NH2(Zr) systems. These synergistic effects between supramolecular components highlight the potential of dye-sensitized MOFs for solar fuel production.