Paper-structured fibrous composites with micrometer-sized pores were prepared using a papermaking technique, followed by in situ synthesis of Pd nanoparticles in the paper matrix using a facile impregnation method. The Pd-containing paper-structured catalysts showed high catalytic activities in solvent-free benzyl alcohol oxidation in a flow reaction system. Highly selective oxidation was achieved using the porous paper-structured catalysts set inside a gas-liquid-solid multiphase reactor. Kinetic and mechanistic studies of various reactions showed that the catalytic activity and selectivity were associated with microfluidic behavior in the fiber-network pores. A uniform distribution of the liquid-phase substrate, i.e., benzyl alcohol, provided high catalytic activity. High selectivity for the oxidation pathways can be attributed to efficient gas-liquid-solid mass transfer toward the thin liquid layer formed at the interface between the alcohol and Pd catalyst inside the porous fiber networks. (C) 2015 Elsevier B.V. All rights reserved.