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Abstract In this work, we employed flame spray pyrolysis (FSP), a high‐temperature synthesis method, to control the formation of Pd structures on the CeO₂support. Multiple types of Pd structures deposited on CeO₂are observed on FSP‐made samples. Our results show that the oxidizing environment during FSP synthesis facilitates the formation of incorporated Pd²⁺structures, along with highly dispersed Pd²⁺, Pd⁰nanoparticles, and Pd° clusters formed under the reducing synthesis condition. Notably, these Pd²⁺species remained stable at temperatures up to 400 °C. The catalysts containing both highly dispersed Pd²⁺nanoparticles and incorporated Pd²⁺species demonstrated superior methane oxidation activity, with higher turnover frequencies than those containing only one type of Pd²⁺structure. However, hydrothermal pretreatment in the presence of water vapor led to partial deactivation, likely due to structural alterations in the Pd species or the interaction with the CeO₂support, which reduced the stability and effectiveness of the active sites. This study underscores the importance of both highly dispersed and incorporated Pd²⁺species in enhancing catalytic performance and highlights the challenges posed by water‐induced deactivation in practical applications. 

The implementation of synthetic polymer membranes in gas separations, ranging from natural gas sweetening, hydrogen separation, helium recovery, carbon capture, oxygen/nitrogen enrichment, etc. , has stimulated the vigorous development of high-performance membrane materials. However, size-sieving types of synthetic polymer membranes are frequently subject to a trade-off between permeability and selectivity, primarily due to the lack of ability to boost fractional free volume while simultaneously controlling the micropore size distribution. Herein, we review recent research progress on microporosity manipulation in high-free-volume polymeric gas separation membranes and their gas separation performance, with an emphasis on membranes with hourglass-shaped or bimodally distributed microcavities. State-of-the-art strategies to construct tailorable and hierarchically microporous structures, microporosity characterization, and microcavity architecture that govern gas separation performance are systematically summarized.