Direct CO₂ capture and conversion have been an active research area in recent years due to its importance in addressing the current global warming/climate change and future depletion of fossil fuels and creating a carbon neutral ecosystem. The benchmark technology for CO₂ capture is the post-combustion amine absorption, which is energy intensive and cost prohibitive to large-scale commercial implementation. In comparison, the CO₂ conversion technologies are still at their infancy with many technical challenges in efficiency and selectivity to be overcome, but primarily being explored in low-temperature solution-based and high-temperature solid-oxide-based electrochemical cells with solar or electrical energy as the input. Here we present a new type of high-temperature membrane reactors operated on mixed conducting chemistry for direct CO₂ separation and instant conversion. In the presentation, we will first discuss the chemistries of three basic types of mixed ionic/electronic conductors designed for CO₂ separation and conversion. We will then present materials and synthesis of the membranes, followed by testing the performance of membrane reactors with mock-up flue gas as the feeding gas and methane/ethane as the sweeping gases. The performances of oxidative conversions of methane and ethane are characterized by conversion rate of the reactants, selectivity and yield of the products and flux density of both reactant and product species. Finally, the fundamental separation and conversion mechanisms will be discussed in detail.