The current reliance on limited petrochemical resources and the resulting ecological outcomes have made the exploration of alternative chemical and energy feedstocks invaluable. As such, the development of sustainable processes with a less harmful total environmental footprint is a global priority. In this context polysaccharide biomass potentially delivers a renewable source of chemical feedstocks which can subsequently be utilised in a range of industries. This work explores polysaccharide hydrolysis as a key step in the development of sustainable technologies utilising renewable biomass feedstocks. Emphasis is made on the development of protocols that entail facile catalyst-product separation and utilise water as the primary solvent. A general overview is provided in Chapter 1. Brønsted acidic imidazolium salt derivatives are explored as recoverable catalyst frameworks for polysaccharide depolymerisation in water. Polysaccharide hydrolysis using an ionic polymer catalyst is explored in Chapter 2. The solid acid catalyst is designed in a step-wise fashion, with an exploration of catalytically active carboxyl-functionalised vinylimidazolium monomers prior to polymerisation of the optimal monomer catalyst. The ionic polymer catalyses starch hydrolysis in water and is easily separable from the reaction. Chapter 3 focuses on an investigation of fluorous-aqueous biphasic catalysis as applied to polysaccharide hydrolysis and reports the synthesis of several highly fluorinated acidic imidazolium salts. Both cation and anion contain fluorinated groups in an effort to impart significant hydrophobicity to the resulting acid catalyst. Strong (SO3H) and weak (COOH) acid groups are used in the construction of the novel catalysts. The fluorous acid catalysts prepared are investigated in the depolymerisation of cellulose and starch. Chapter 4 explores several carboxyl-functionalised acidic imidazolium salts for application to thermomorphic (temperature switchable) acid catalysis in water. A suitable thermomorphic acid catalyst is identified from a screening process and is found to be active in the hydrolysis of both cellulose and starch. The catalyst possesses a suitable solubility profile in water, with precipitation occurring near ambient temperatures, for separable acid catalysis in water.