Facile graft copolymer template synthesis of mesoporous polymeric metal-organic frameworks to produce mesoporous TiO₂: Promising platforms for photovoltaic and photocatalytic applications

Mesoporous polymeric metal-organic frameworks (mesoporous polymeric MOFs) are prepared on fluorine-doped tin oxide (FTO) substrate using hydrophilic terephthalic acid as the ligands, titanium isopropoxide as polymeric MOF precursors, and amphiphilic graft copolymers (i.e., poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM) as structure-directing agents. The hydrophilic POEM chains in amphiphilic graft copolymers interact with the hydrophilic ligands and polymeric MOF precursors. Following thermal treatment at 500 °C, mesoporous polymeric MOFs are transformed to mesoporous TiO₂ with high specific surface area and crystallinity, suitable for photovoltaic and photocatalytic applications. Solid-state dye-sensitized solar cells (ssDSSCs) and dye-sensitized solar cells (DSSCs) fabricated with mesoporous TiO₂ photoanodes have efficiencies of 7.45 and 8.43 % at 100 mW/cm², which is much higher than that of ssDSSCs and DSSCs with photoanodes of conventional TiO₂ (5.36 and 7.14 %), respectively. The enhanced efficiency is attributed to good interconnectivity, larger surface area, and high porosity of the mesoporous TiO₂, which results in suppressed interfacial charge recombination loss, enhanced electron transport, increased dye loading, and facilitated penetration of the electrolytes. Mesoporous TiO₂ shows excellent activity as a photocatalyst for the degradation of humic acid under UV light irradiation.