“…9,12 Solid acid catalysts can overcome the drawbacks of traditional liquid acids and have gained increasing attention. [13][14][15][16] A series of heterogeneous solid acids have been developed, including sulfonated solid acids, [17][18][19][20] zeolites, 21 metal oxides, 22 cation-exchange resins, [23][24][25] hetero-poly acids, 26,27 and other materials. 28,29 However, there is an obvious heterogeneous interface between cellulose and solid acids which thus extremely weakens the contact catalysis.…”