Heterogenous photocatalysis is an attractive enabler of the efficient execution of different important environmental (e.g., production of hydrogen and C-based fuels) and organic reactions utilizing solar energy. In a typical batch reactor, a heterogenous photocatalyst is dispersed in a given solution together with reactants, and upon illumination, a chemical reaction occurs. Despite its simplicity, the overall process faces some challenges related to the intrinsic nature of the reaction conditions: light penetration significantly decreases with distance, the photocatalyst should be continuously stirred to avoid sedimentation, separating the products from the photocatalyst is not trivial, the catalyst is hard to recycle, the reaction is dependent on the concentration of starting reactants, and scalability is questionable.

An alternative approach is to use a panel based on a photocatalytic material. This configuration improves light management and enables easy recycling and scalability, similar to that of solar cells. Furthermore, the photocatalyst panel can be easily incorporated into a continuous-flow reactor, facilitating constant reactant feed and product separation. In recent years, polymeric carbon nitride (CN) materials have emerged as a class of photocatalysts for many reactions, from solar fuel production to biomass conversion and complex organic transformations. Nevertheless, most studies have focused on using CN powders as heterogeneous photocatalysts. Some pioneering works showed the utilization of CN panels, mainly for H₂ production. However, all these panels were prepared by drop casting or screen printing a synthesized catalyst with a polymer containing perfluoro groups (i.e., Nafion) or a SiO₂ binder on frosted glass or steel plates. The use of a binder can lead the photocatalyst to detach from the substrate because of the formation of radicals during the reaction (e.g., reactive organic species, ROS); this happens mainly in organic chemical reactions, where the ROS intermediates might react with the binder and give unwanted side products.

This talk will introduce a facile and scalable method for binder-free melon-type flat and porous polymeric carbon nitride (CN) panels with tunable structural and photophysical properties. The CN panel exhibits excellent photoactivity in a homemade bench-scale reactor for four important catalytic reactions: the production of hydrogen peroxide in concentrations that meet industrial requirements, biomass-derived 5-hydroxymethyfurfural (HMF) oxidation to 2,5-diformylfuran (DFF) under visible light, resulting in 75% HMF conversion with a DFF yield of 13% after 24 h under continuous-flow conditions (1 mL min^–1); continuously-monitored water purification via UV–vis spectroscopy; and hydrogen production. The binder-free deposition method and its excellent photocatalytic activity broadens avenues for CN photocatalyst-based and other semiconductor panels towards multiple sustainable energy-related applications.