Biomass photorefining into value-added chemicals and fuels is a promising approach towards carbon neutrality. As one of the most abundant renewable resources, biomass has great potential to address increasing energy demands through environmentally benign processes, along with the production of value-added chemicals. Polymeric carbon nitride (CN), comprised of a 2D network of condensed heptazine/triazine (C6N7/C3N3) cores, has shown great potential for the photoreforming of biomass derivatives due to its intriguing physicochemical and optical properties. Since cellulose, a major component of lignocellulosic biomass (40%-60%), is composed of glucose units, glucose serves as an ideal model for studying photoreforming processes. This thesis initially begins by studying the intrinsic mechanisms of selective glucose photoreforming, with or without C-C bond cleavage via different reaction pathways, and then extends the scope to include cellobiose and cellulose. Beyond photocatalysis, hybrid catalytic systems (e.g., photo-bio, photo-electro, or bio-photo/electro) hold great potential for use in cellulosic biomass valorization as well as other potential applications with industrial market potential. Firstly, crystalline CN with Lewis acid-base sites enables glucose isomerization into fructose, while a dual-functional CN photocatalyst facilitates glucose photo-oxidation to gluconic acid. Further oxidation to glucaric acid is achieved using alkalized CN with TEMPO mediation. Then, glucose photoreforming with C-C bond cleavage is investigated. For example, gold nanoparticle-modified CN (AuCN) selectively generates superoxide radicals (•O2−) to cleave the C1-C2 bond, producing arabinose. Additionally, C3-C4 bond cleavage produces glycerol under the effect of nucleophilic dimethyl sulfoxide, which can be further oxidized into value-added chemicals. Beyond glucose, the photoreforming of cellobiose into gluconic acid and syngas under acidic conditions is investigated. Then direct cellulose photorefining is demonstrated using oxygen-doped CN, and a photobiocatalytic approach is explored, coupling cellulase enzymes with a modified CN photocatalyst. Finally, a bio-photo/electro hybrid catalytic system is further developed to address the limitations of photocatalysis, paving the way for industrial-scale applications. This hybrid system not only facilitates the oxidation of glucose into organic acids but also integrates NADH-driven enzymatic reactions, offering a new approach for biomass utilization while expanding the potential of typical enzymes for industrial-scale chemical production.