This paper reports the preparation of mixed matrix membranes (MMMs) by incorporating a two-dimensional zeolitic imidazolate framework-L (ZIF-L) into a highly gas permeable hydroxyl group-containing polyimide (PI) for hydrogen separation. ZIF-L has a leaf-shaped morphology with excellent CO2 adsorption properties due to strong interaction between ZIF-L and CO2 molecules. The dispersion of ZIF-L crystals in the polymer phase increased CO2 adsorption and restricted CO2 transport through MMMs, resulting in a significant increase of H-2 selectivity over CO2. The gas transport properties of MMMs with a ZIF-L loading up to 20 wt% were investigated, and the results showed such MMMs had a H-2 permeability of 260 Barrers and ideal H-2/CO2 selectivity of 13.4 at room temperature. The membranes presented here have the potential for large-scale fabrication for hydrogen separation applications.