Separating and capturing carbon dioxide from mixed gas streams is a first and critical step in carbon sequestration. To be technically and economically viable, a successful separation method must be applicable to industrially relevant gas streams at realistic temperatures and pressures as well as be compatible with large gas volumes. The work being pursued by this Project Team involves the development of polymeric-metallic composite membranes with a polybenzimidazole (PBI)-based selective layer that can purify hydrogen and capture carbon at high temperatures.  Our approach focuses on a pre-combustion capture approach that integrates the high-temperature polymeric-metallic composite membranes into an advanced Integrated Gasification Combined-Cycle (IGCC) process. The primary project objective is the development of polymeric-metallic composite membrane structures that achieve the critical combination of high selectivity, high permeability, and chemical and mechanical stability at elevated temperatures (>150 °C). Stability requirements are focused on tolerance to the primary synthesis gas components and impurities at various locations in the process. The project team has made significant strides towards demonstrating the technical and economic feasibility of capturing CO₂ from large point sources, such as power plants, via both long-term (300+ day) testing at the High Temperature Membrane Development and Test Facility at LANL and out-of-the-laboratory testing at a pressurized natural gas fuel processor.  We will describe the results from the aforementioned prototype testing of separation modules operating under industrially relevant conditions and discuss the challenges involved in successfully developing this technology. This project supports the U.S. DOE National Energy Technology Sequestration Program project portfolio focused on the capture and separation of CO₂ from the power sector.