In this study, the effect of surface basicity on the structure and catalytic activity of chromium based metal organic framework, MIL-101, was investigated. Increase in surface basicity was achieved by functionalization using four different deep eutectic solvents (DESs) and ethylene diamine for comparison. Also the superior properties of DES for functionalization was highlighted. The characterization of samples was performed using BET, XRD, FTIR, SEM, TGA techniques and zeta potential measurements. The catalytic activity of raw MIL-101 and functionalized MIL-101 samples were tested in Knoevenagel reaction performing between malononitrile and benzaldehyde. The maximum conversion values were achieved as 98.3, 99.5 and 100% for MIL-101, MIL-101-ED and MIL-101-D1, respectively when the reaction conditions were 1:1 reactant molar ratio, 5 wt% of catalyst loading and at 70 degrees C. Besides achieving a high conversion, DES was found to be advantageous as grafting agent due to its having low volatility, high biodegradability and environmental friendly nature when compared to the harmful and toxic solvents.