A facile, cost-effective and two-step strategy is developed to fabricate a nanoporous graphene (Gr) thin film for enhanced gas sensing at room temperature. Microwave plasma enhanced chemical vapor deposition (MPCVD) is first exploited to synthesize 3D Gr spherical structures, which are subsequently fragmented by ultrasonic treatment in liquid. Deposition of the fragmented 3D Gr structures on a substrate leads to the formation of a nanoporous Gr thin film, which is exploited as a conductance channel to detect CO2 and NH3 with impressive performance, including high sensitivity, linearity, low limit of detection (LOD) and reversibility. Compared with traditional gas sensors based on planar Gr sheets, this nanoporous Gr thin film displays remarkable 4.2 times higher response to CO2 and 10.4 times larger response to NH3, demonstrating the advantage of nanoporous Gr in improving the sensitivity. CO2 with a wide concentration range from 20 to 1000 ppm is detected with good linearity and repeatability. Furthermore, NH3 with the low concentration of 2 ppm is detected with a good response of 19.2%. Note that ultrafast and complete recovery is achieved at room temperature, bypassing the requirement of external stimulus to facilitate the recovery. In addition, long-term stability and immunity to high humidity are achieved. This work underscores the efficacy of a nanoporous Gr thin film structure in improving gas sensing performance of Gr materials. (C) 2017 Elsevier B.V. All rights reserved.