The Hy-MASS concept: hydrothermal microwave assisted selective scissoring of cellulose for in situ production of (meso)porous nanocellulose fibrils and crystalsElectronic supplementary information (ESI) available: Experimental data, ATR-IR, Py-GC-MS, CHN, HPLC sugar analysis and ICP-OES. See DOI: 10.1039/c7gc01378g

The hydrothermal microwave-assisted selective scissoring (Hy-MASS) of depectinated orange peel residues (OPR), produced via conventional acid hydrolysis and acid-free microwave processing, to yield (meso)porous nanocellulose fibrils and crystals simultaneously in the absence of additional auxiliary reagents and/or mechanical treatment is reported. In the stepwise microwave hydrothermal treatment (MHT) of OPR from 120 °C-200 °C at 20 °C intervals, release of residual pectins and hemicelluloses is observed up to 180 °C producing nanocellulose fibrils (3-15 × 500-2000 nm). Beyond 180 °C, selective leaching/hydrolysis of amorphous regions occur to yield nanocellulose crystals (200-400 × 40-50 nm) and crystallites (5-15 × 40-50 nm). This selective, step-wise scissoring process is termed Hy-MASS Concept . Structure, morphology and properties of (meso)porous nanocellulose are strongly influenced by pectin extraction methodology employed. With acid depectinated OPR, deconstruction of the lignocellulosic matrix via microwave is hastened by approx. 20 °C with respect to acid-free microwave depectinated OPR. T d of acid depectinated nanocelluloses (CMC) is ca. 350 °C compared to microwave depectinated nanocelluloses (MMC, T d , varies 342-361 °C). Nanocellulose produced via microwave pre-treatment is (meso)porous: BJH pore size 5-35 nm; BET surface area, 1.5-107 m 2 g −1 , and; BJH pore volume, 0.01-0.27 cm 3 g −1 , when compared to acid pre-treated counterparts. The crystallinity index of CMC and MMC increases in two stages, 120-140 °C ( ca. 8%) and at 180-200 °C (5-9%). XRD revealed presence of calciuim salts, most likely calcium oxalate. The hydration capacities of nanocelluloses (12-23 g water per g sample) are much higher than their precursors or literature citrus nanocellulose. The hydrothermal microwave-assisted selective scissoring (Hy-MASS) of depectinated orange peel residues (OPR) to yield (meso)porous nanocellulose fibrils and crystals simultaneously in the absence of auxiliary reagents and mechanical treatment is reported.