Carbon-dots-referenced metal-organic frameworks for chemical sensing of tumor/mood biomarker 5-hydroxyindoleacetic acid in human urine: Covalent grafting blue-emitting carbon dots onto red-emitting MOF

•Blue-emitting carbon dots were covalently grafted onto red-emitting MOF to form a composite sensing platform.•5-HIAA replaced and released the carbon dots which showed strong blue emission, but MOF red emission was quenched by 5-HIAA thermal relaxation.•A linear working calibration curve was fitted as F/F0 = 0.588 + 1.598*[5-HIAA], R2 = 0.999, with LOD of 0.3 μM and good selectivity.•The practical sensing performance of BCD@EuBTC for 5-HIAA in human urine was confirmed, with recovery of 103%.