In this work, a zeolitic imidazolate framework-8 (ZIF-8)-coated coupled resonant sensor was fabricated using a solvent-free method. The solvent-free method avoids the use of solvents for ZIF-8 synthesis, which eliminates the risk of device contamination, corrosion, or destruction. This process enables batch fabrication of ZIF-8-coated coupled resonators at wafer level. By tracking shifts in frequency and amplitude ratio, the sensor demonstrates strong responses to ethanol vapor of different concentrations and exhibits good reversible detection ability. The normalized sensitivity using amplitude ratio shift as an output metric is $6.06\times10$ $^{\mathbf{-3}}$ at low ethanol vapor concentrations (2%-7.5%), which is nearly six times that using frequency shift ( $1.06\times10$ $^{\mathbf{-3}}$ ). For higher ethanol vapor concentrations (10%-60%), the normalized sensitivity using amplitude ratio shift is $2.66\times10$ $^{\mathbf{-3}}$ , almost 40 times that using frequency shift ( $6.73\times10$ $^{\mathbf{-5}}$ ). Given the significantly enhanced sensitivity, the ZIF-8-coated coupled resonant sensor shows promising potential for ultra-sensitive gas sensing.