Engineering of catalytically active sites in photoactive metal–organic frameworks

Metal-organic frameworks (MOFs) are hybrid and porous materials with ample opportunities for photocatalytic applications. Their structural components are suitable for precisely engineering photoactive elements of various kinds and analysing energetic processes at different scales; furthermore, their large surface area can be decorated with non-structural elements to adjust the parental properties as needed. In this regard, various organic and inorganic catalytic elements have been successfully modulated in localized sites of photoactive MOFs. In spite of the obvious attractiveness, the functionalization of MOFs with effective and localized catalytically active components can only be achieved under controlled conditions and with the respect of precise assumptions. Accordingly, we want to provide a series of guidelines based on theoretical and experimentally proven concepts concerning the engineering of catalytically active sites located in the distinctive MOF components. Apart from discussing the general concepts and the instrumental role of photocatalytic elements in advanced materials, notes are prepared on the synthesis and characterization procedures involved in the intercalation of localized catalytic sites (CSs) within the MOF lattice. Special emphasis is given to the methods employed to immobilize these CSs in the distinctive structural components of MOF while favouring structural retention of the latter. At the same time, a distinction is made for the multifarious catalytic elements according to their chemical classification; to this end, special mention is made of the instrumental techniques used to describe their structural composition. Photogenerated charge transfer mechanisms are illustrated on the basis of the procedures chosen by the authors. In conclusion, this review will comprehensively examine illustrative photocatalytic reactions and performance of photoactive MOFs with CSs located at distinctive structural sites.