Metal–organic frameworks and derived materials as photocatalysts for water splitting and carbon dioxide reduction

One of the currently proposed solutions for finding alternatives to fossil fuels and combating environmental pollution concerns the development of advanced materials for clean and renewable energy applications. An ongoing focus is devoted to the design of semiconductor-oriented heterogeneous photoelectrocatalytic, photocatalytic and electrocatalytic systems using fuel cells. In this regard, photocatalytic water splitting and carbon dioxide reduction stand as the two most promising processes for solving the energy crisis and mitigate the environmental pollution. However, these processes still demand for cost-efficient, stable, and environmentally benign photocatalysts. Metal–organic frameworks (MOFs) have emerged as adjustable and multipurpose materials that are now intensively investigated as a podium for applications in clean energy, including photocatalytic H₂O splitting and CO₂ reduction. Apart from representing an array of intrinsic structural and physicochemical characteristics, MOFs are well susceptible for various post-synthetic modifications to address specific challenges. Despite years of research in this field and a good number of seminal studies, further efforts should be geared toward the improvement of light absorption and stability of MOFs, which are the principal challenges that should be overcome. In this review, various strategies for designing MOFs and derived materials for advanced photocatalytic H₂O splitting and CO₂ reduction processes are discussed in detail, with a particular focus on the most recent progress in this area. Fundamental principles of photocatalysis, thermodynamics and kinetics, mechanistic features, and synthetic strategies for MOFs and derived nanomaterials and composites are exemplified to create a current state-of-the-art perception of this broad and highly important research topic. Industrial perspectives and projections on future research using MOFs and their composite photocatalytic materials are also elucidated. This review will be of assistance and a wake-up call to the scientific community in the field where the design and development of MOFs is blended with the materials science toward creating new solutions for clean energy production, using water splitting and carbon dioxide reduction as two key processes of paramount significance.