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Flexible and hierarchical nanostructured Pd/SiO 2 -TiO 2 nanofibrous catalytic membranes were fabricated via combining electrospinning technique and a two-step hydrothermal method. The size and distribution of TiO 2 nanorods immobilised on SiO 2 nanofibrous membranes can be regulated via adjusting the dosage of TiCl 3 solution in the first step hydrothermal process. When using an optimal TiCl 3 solution dosage of 0.2 mL, a hierarchical structured Pd/SiO 2 -TiO 2 -0.2 nanofibrous catalytic membrane with uniformly dense TiO 2 nanorods loaded on SiO 2 nanofibers is obtained, and still shows good tensile strength and flexibility. The catalytic activity of Pd/SiO 2 -TiO 2 -0.2 increases 5 times as compared to Pd/SiO 2 -TiO 2 -0 in the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP). The modification with TiO 2 nanorods can provide more surface areas for loading the Pd nanoparticles, thereby increased active sites. The three-dimensional open-cell network stacked and assembled by thousands of SiO 2 nanofibers and TiO 2 nanorods enhances the contact between the reactants and Pd nanoparticles. Both aspects contribute the superior catalytic activity of Pd/SiO 2 -TiO 2 -0.2. Furthermore, a continuous and complete conversion of PNP to PAP can be stably operated over 240 min in a gravity-driven catalytic membrane reactor constructed by Pd/SiO 2 -TiO 2 -0.2.

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Aiming at the design and preparation of highefficiency catalysts for the selective hydrogenation of phenol, the hierarchically porous Pd@CNF catalysts were fabricated by oxygen-activating ZIF-67/PAN composite nanofibers with O 2 as the oxidant during high-temperature pyrolysis, followed by acid etching and Pd loading. Appropriate initial oxygen concentration and Co 2+ molar concentration are conducive to the fabrication of hierarchically porous carbon nanofibers (CNFs) with a high mesopore and macropore ratio, increased ether-type oxygen content, and good one-dimensional (1D) morphology, which enhance the dispersion and anchoring of Pd, increase the strength of basic sites and H 2 adsorption, and improve the mass transfer and dispersibility in cyclohexane.