Herein, a new phenomenon of enhanced electrochemiluminescence (ECL) emission by restricting intramolecular motion in the 2D ultra-thin Zr12-adb (adb = 9,10-anthracene dibenzoate) metal-organic framework (MOF) nanoplate was discovered for the first time. The coordination immobilization of adb in porous ultra-thin Zr12-adb nanoplate endowed the Zr12-adb excellent ECL performance, including stronger ECL signal and higher ECL efficiency relative to those of H2adb monomers and H2adb aggregates. In the 2D Zr12-adb nanoplate, the bridging ligand adb was stretched and fixed between two Zr12 clusters, which restricted intramolecular rotations and suppressed unnecessary energy loss caused by self-rotation, thereby remarkably improved the ECL intensity and efficiency. More importantly, the porous ultra-thin structure of Zr12-adb MOF nanoplate not only allowed the coreactants to diffuse into the MOF interior, making both internal and external adb be excited, but also shortened the migration distance of electrons, ions, coreactants and coreactant intermediates, which further improved the ECL efficiency of Zr12-adb and overcame the shortcoming of H2adb aggregates in which the internal luminophores were not easily excited. Regarding the excellent ECL properties above, Zr12-adb nanoplate was selected as a new ECL emitter incorporated with the bipedal walking molecular machine together to fabricate a biosensor for sensitive detection of mucin 1. The enhanced ECL by restriction of intramolecular motions in MOFs provided a new pathway to improve ECL intensity and efficiency, which lighted up a lamp for the design and manufacture of high-performance ECL materials based on MOFs, thus offering new opportunities to develop ultrasensitive ECL biosensors. This work proposed a new and efficient strategy to enhance ECL for the first time, named RIM by MOFs for ECL enhancement, which not only opened up a new horizon for exploring novel strategies to enhance ECL, but also expanded the application of MOFs in bioassays and provided an unprecedented idea to devise outstanding ECL emitters. Display omitted •A new and efficient strategy was proposed for the first time to enhance ECL, named RIM by MOFs for ECL enhancement.•Zr12-adb nanoplates was synthesized as a bright ECL emitter to construct highly sensitive and selective ECL biosensors.•The developed ECL biosensor realized ultrasensitive detection for MUC1.