▎ 摘　　要

Carbon-based quantum dots (QDs) with ultralow dimensions and controllable surface chemistry have unique properties appealing to diverse applications. Here, we disclose a high-throughput transformation of spent coffee grounds into uniform QDs assembled by few-layer graphene oxide nanosheets, employing a microwave-assisted strategy under aqueous reaction conditions. Given the low dimensions (30 nm) and high structural integrity, the highly oxygenated QDs exhibited excellent dispersibility in water with tunable fluorescence. The structural attributes of QDs conferred excellent affinity to graphene nanosheets, permitting aqueous processing of nanoporous graphene membranes applicable to removing a broad spectrum of water pollutants ranging from organic compounds to heavy metals while sustaining a high flux rate. The proposed "trash-to-treasure" strategy opens up new possibilities for aqueous processing of nanoporous graphene membranes with great potential in the environmental field.