Through structural design, a series of bifunctional ionic liquids (BFILs) containing sulfonic acid (–SO₃H) and sulfhydryl groups (–SH) were synthesized and characterized by NMR and MS. The acidity of these BFILs was measured by the Hammett acidity (H₀) and the effective sulfhydryl molar content of BFILs was determined by Ellman's method. Moreover, BFIL's catalytic properties in the condensation reaction of 9-fluorenone and phenol were studied. BFIL catalyst 6c can achieve nearly 100% conversion of 9-fluorenone with a high selectivity of 9,9-bis(4-hydroxyphenyl) fluorene (95.2%).