Membrane distillation is a process that utilizes differences in vapor pressure to permeate water through a macro-porous membrane and reject other non-volatile constituents present in the influent water. This review considers the fundamental heat and mass transfer processes in membrane distillation, recent advances in membrane technology, module configurations, and the applications and economics of membrane distillation, and identifies areas that may lead to technological improvements in membrane distillation as well as the application characteristics required for commercial deployment.

Metal organic frameworks (MOFs) are hybrid crystalline materials, exhibiting high specific surface areas, controllable pore sizes and surface chemistry. These properties have made MOFs attractive for a wide range of applications including gas separation, gas storage, sensing, drug delivery and catalysis. This review focuses on recent progress in the application of MOF materials as catalysts for CO₂ conversion through chemical fixation, photocatalysis and electrocatalysis. In particular, this review discusses the co-relationship between the physicochemical properties of MOF materials including their catalytic performance as well as their stability and recyclability under different reaction conditions, relevant to CO₂ conversion. Current modification techniques for improving MOF performance are highlighted along with the recent understanding of their electronic properties. The limitations of MOF based catalysts are also discussed and potential routes for improvement are suggested.

Photocatalysis with nanostructured semiconductors is emerging for environmental remediation.

Downsizing metal–organic framework (MOF) crystals into the nanoregime offers a promising approach to further benefit from their inherent versatile pore structures and surface reactivity. In this article, downsizing is referred to as the deliberate production of typical large MOF crystals into their nanosized versions. Here, we discuss various strategies towards the formation of crystals below 100 nm and their impact on the nano-MOF crystal properties. Strategies include an adjustment of the synthesis parameters (e.g., time, temperature, and heating rate), surface modification, ligand modulation, control of solvation during crystal growth and physical grinding methods. These approaches, which are categorized into bottom-up and top-down methods, are also critically discussed and linked to the kinetics of MOF formation as well as to the homogeneity of their size distribution and crystallinity. This collection of downsizing routes allows one to tailor features of MOFs, such as the morphology, size distribution, and pore accessibility, for a particular application. This review provides an outlook on the enhanced performance of downsized MOFs along with their potential use for both existing and novel applications in a variety of disciplines, such as medical, energy, and agricultural research.