Gas transport properties of hyperbranched polybenzoxazole (PBO) - silica hybrid membranes were investigated. The hyperbranched PBO - silica hybrid membranes were prepared via in-situ silylation method and sol-gel reaction. Thermal decomposition temperature of the hybrid membranes increased with increasing silica content, indicating improved thermal stability brought by the hybridization with silica. The hyperbranched PBO silica hybrid membranes showed higher gas permeability than corresponding linear-type PBO silica hybrid membranes with similar chemical structure. It was worth noting that both CO2 permeability and CO2/CH4 selectivity of the hyperbranched PBO silica hybrid membranes were increased with increasing silica content across the upper bound trade-off line for CO2/CH4 separation. The prominent CO2/CH4 separation ability of the hyperbranched PBO silica hybrid membranes might be achieved by large amounts of free volume holes, that were fundamentally brought by a characteristic hyperbranched structure and additionally crated around polymer/silica interfacial area, equipped with unique distribution and interconnectivity advantageous for a size-selective CO2/CH4 separation. (C) 2016 Elsevier B.V. All rights reserved.