The demand for sustainable energy has motivated the development of artificial photosynthesis. Yet the catalyst and reaction interface designs for directly fixing permanent gases into liquid fuels are still challenged by sluggish mass transfer and catalytic kinetics at the gas-liquid-solid three-phase boundary. Here, we report that breathable metal-organic framework (MOF) membranes decorated with metal single-atoms (SAs) can synergistically promote the diffusion, adsorption, and activation of gas molecules (e.g. CO2, O2) to boost the photocatalytic conversion of them into liquid fuels. With Ir SAs as active centers, the defect-engineered MOF (e.g. NH2-UiO-66) matrixes can efficiently harvest visible light and sensitize the electronically tailored Ir SAs for reducing CO2 to HCOOH with the high activity of 0.51 mmol gcat-1 h-1 at the conventional three-phase reaction interface. Furthermore, the breathable SA/MOF membranes can directly convert humid CO2 gas into HCOOH at the high-throughput gas-solid interfaces, presenting a near-unity selectivity and an unprecedented activity of 3.38 mmol gcat-1 h-1. Similarly, with Pd SAs as active centers, the SA/MOF membrane can catalyze the O2-to-H2O2 conversion with an ultrahigh activity of 10.4 mmol gcat-1 h-1 under visible light, suggesting the wide applicability of our catalyst and reaction interface designs.