Porphyrin-based metal–organic frameworks (MOFs) have great photocatalytic potential due to their good photosensitivity. Their photocatalytic performance is not only determined by molecular structure but also by morphology. Flower-like MOFs are considered to be good materials for catalysis due to their larger specific surface area, more exposed active sites, and good stability. Here, we first proposed a method to synthesize flower-like porphyrin-based MOFs using trifluoroacetic acid as a morphology control agent. These MOFs had a large BET surface area (605.04 m² g⁻¹), a stable structure and a complete morphology. Meanwhile, we discussed their self-assembly process and mechanism in detail. In addition, we studied the photocatalytic performance of flower-like porphyrin-based MOFs and found that the flower-like Cu-TCPP (TCPP = tetrakis(4-carboxyphenyl)porphyrin) has excellent photocatalytic activity. Its photodegradation efficiency toward the cationic dye rhodamine B reached 88% within 100 min and the sample still maintained its stable catalytic activity and complete flower-like morphological structure after five repeated uses. Furthermore, this synthetic strategy can be extended to control the morphology of other MOFs.