Phthalic Acid-Terminated Hyperbranched Poly(ether ketone) as a Solid Acid Catalyst for Cellulose Hydrolysis

Hydrolysis of β-1,4-glycosidic bonds in cellulose is a key step for producing biofuels and value-added chemicals from lignocellulosic biomass. Efficient heterogeneous catalysts for this transformation are still limited. Here, we report a hyperbranched poly(ether ketone) terminated with phthalic acid groups as a solid acid catalyst for cellulose hydrolysis. The polymer was synthesized by AB2-type polycondensation of 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, followed by cross-linking with diphenyl ether. The aromatic backbone and the cross-linked network endowed the polymer with sufficient stability to withstand hydrothermal conditions at 230 °C, under which it exhibited catalytic activity in the hydrolysis of cellobiose and cellulose. Furthermore, the catalyst retained phthalic acid groups as active sites and demonstrated recyclability over multiple runs. This study highlights the potential of terminally functionalized hyperbranched polymers as next-generation solid acid catalysts for biomass conversion.