Cellulose Degradation by Infrared Free Electron Laser

We introduce a green approach to obtain glucose and low-molecular-weight saccharides directly from the cellulose aggregate by using near- and mid-infrared free electron lasers (IR-FELs). The IR-FEL is a synchrotron radiation based picosecond pulse laser where the oscillation wavelengths are tunable from 3 to 10 μm. Electrospray ionization mass spectroscopy analysis showed that mass peaks of glucose (203 Da), cellobiose (365 Da), trisaccharide (527 Da), and tetrasaccharide (689 Da) were clearly detected as each sodium ion adduct in the soluble fraction after the powdered cellulose was serially irradiated by the IR-FEL tuned to 9.1 μm (νC–O) following 7.2 μm (δH–C–O) or 3.5 μm (νC–H). The production yields of these saccharides were higher than those obtained by the single irradiation at 9.1 μm, as shown by the mass chromatogram analysis. The cleavage of the glucoside bonds was revealed by synchrotron radiation infrared microscopy analysis: the infrared absorption peak of the C–O bonds at 1100 cm–1 was obviously reduced, and the bandwidth of the broad peak of O–H bonds at 3400 cm–1 was shortened after those irradiations. The laser irradiation system suggested herein is based on the vibration mode selective multiphoton absorption reaction and requires no cosolvents and no high temperatures and pressures to exert the irradiation effect. One day of operation can process several hundred milligrams of the solid cellulose sample at the current laboratory scale.