Semiconductor-mediated heterogeneous photocatalysis is a promising technology for water purifications without generating harmful by-products. The photocatalyst with designed physicochemical properties is the key in the process. Utilization of particulate photocatalysts will create some technological problems, such as difficulty in recycling and management. Thus, cost-effective methods for mass production of highly active photocatalysts that can be operated in an industrial photoreactor with less energy consumption and harmless subsequent consequences are increasingly attracting research attention. Photocatalysts with controllable morphologies at a wide range of scales shall be taken into account in designing the photocatalyst. This review article features recent research progress towards the design and preparation of porous photocatalysts with prescribed structural, compositional, and morphological properties suitable for use in a photocatalytic reactor for water treatment via advanced oxidation processes. With a brief introduction of the important features of a porous photocatalyst in industrial reactors, the review highlights various synthetic strategies for fabricating porous photocatalysts with well-defined microscopic morphologies and nano/meso-scopic active nanobuilding blocks. The synthesis–component–structure–property relationship working in photocatalyst design is discussed. Immobilization of photocatalysts on different porous substrates is highlighted. The perspectives of designing photocatalysts for industrial applications are suggested.