“…Although the CTH process is relatively novel for the synthesis of FOL, this was discovered nearly 100 years ago by Meerwein, Ponndorf, and Verley. − The first studies were carried out through homogeneous catalysis, using some metal complexes and/or alkoxides, which act as Lewis acid sites. , Nevertheless, heterogeneous catalysts have progressively appeared as a greener alternative to the traditional homogeneous ones, because they are easily separable and can be reused. Several solid Lewis acid, or basic, catalysts, such as ZrO 2 , − Al 2 O 3 , ,, Fe 2 O 3 , , MgO, ,− Zr-, − Hf-, , or Sn-zeolites ,,, and Zr-, − Ru-modified zirconium hydroxide, Ni- and Ni–W/active carbon, or Hf- MOFs − have been proposed for the CTH of FUR.…”