Finnally, the whole liner packed stainless steel autoclave and heated at 150 C for 48 h. The reactor was cooled to room temperature to separate the solid and washed with DMF and methanol, respectively, and the yellow solid was obtained (NH2-MIL-125 (Ti)). X-ray diffraction (XRD) patterns indicates that a narrow and sharp diffraction peak indicates that the precursor has a good crystallinity (Figure , black line), which is consistent with the literature. Delightly, XRD characterizations of the reused catalyst still remained same diffraction peak and demonstrated high structural stability (Figure , red line). As expected, the little spectral changes were observed from UV/Vis ab-sorption upon fresh and recycled catalyst (Figure ). As shown in Figure , a significant absorption was observed in the wavelength band of 400-500 nm, that is why the catalyst in 450 nm light exhibit the best catalytic effect. Meanwhile, Transmission electron microscopy (TEM) observation for NH2-MIL-125 (Ti) as a representative suggests that it has a good crystal structure and rule shape (Figure ). Therefore, this is further approved by scanning electron microscope (SEM) (Figure ). The elemental energy dispersive X-ray (EDX) mapping indicates uniform distribution of various elements (Figure ). With the optimized reaction conditions in hand, we evaluated a range of substrates for N-methylation of amines with CO2. As we know, for the amines, we studied fatty amines and aromatic amines with various substituents, including electron withdrawing group and electron donating group, which react with CO2 to give the corresponding desired methylamine in excellent yields (Table ). For instance, methyl substituted anilines, including para-, ortho-, meta-, all were obtained in excellent conversion above 80  and good selectivity above 95  (Table , entry 3-5). Aromatic amines with electron-withdrawing groups such as ;N-methyl-4-fluoroaniline was well tolerated , giving N,N-Dimethyl-4-fluorobenzeneamine conversion of up to 75 without by-product(Table , entry 7). Besides, aliphatic amines and large spatial displacement chain aromatic also converted to the corresponding methylamine in high selective conversions (Table , entry 9-10). Table . Substrate scope of N-methylation a .