3D-Printed MOF Monoliths:Fabrication Strategies and Environmental Applications

Metal-organic frameworks(MOFs)have been extensively considered as one of the most promising types of porous and crystalline organic-inorganic materials,thanks to their large specific surface area,high porosity,tailorable structures and compositions,diverse functionalities,and well-controlled pore/size distribution.However,most developed MOFs are in powder forms,which still have some technical challenges,including abrasion,dustiness,low packing densities,clogging,mass/heat transfer limitation,environmental pollution,and mechanical instability during the packing process,that restrict their applicability in industrial applications.Therefore,in recent years,attention has focused on techniques to convert MOF powders into macroscopic materials like beads,membranes,monoliths,gel/sponges,and nanofibers to overcome these challenges.Three-dimensional(3D)printing technology has achieved much interest because it can produce many high-resolution macroscopic frameworks with complex shapes and geometries from digital models.Therefore,this review summarizes the combination of different 3D printing strategies with MOFs and MOF-based materials for fabricating 3D-printed MOF monoliths and their environmental applications,emphasizing water treatment and gas adsorption/separation applications.Herein,the various strategies for the fabrication of 3D-printed MOF monoliths,such as direct ink writing,seed-assisted in-situ growth,coordination replication from solid precursors,matrix incorporation,selective laser sintering,and digital light processing,are described with the relevant examples.Finally,future directions and challenges of 3D-printed MOF monoliths are also presented to better plan future trajectories in the shaping of MOF materials with improved control over the structure,composition,and textural properties of 3D-printed MOF monoliths.

The challenges of a Big Data Earth

The potential of big data fused with the vision of a digital Earth offers powerful opportunities to deepen understanding of the whole Earth system and the management of a sustainable planet.It is important to stand back from often confusing detail to clarify what those opportunities are and how they might be seized.The essential scientific potential of data,big or small,is to reveal patterns,which have often been the fundamental first step in stimulating inquiry,leading to new questions,new perspectives and potentially to new answers.The digital revolution has created a“digital microscope”that permits us to see patterns that have not been seen before,and when coupled with machine learning technologies to analyse them in creating statistical predictions of the behaviour of both human and non-human systems.These potentials converge with the imperative to represent an Earth system with interacting non-human and human components,as a vital contribution to the understanding and actions required in working towards planetary sustainability.But a digital Earth is also capable of being represented mathematically as a digitally networked phenomenon,analogous to an analogue computer,and should be an important target for a Big Earth Data Journal.We should also return to Al Gore’s vision of an accessible digital Earth with wide usability.Pre-determining the separate functions of parallel digital Earths risks losing one of the great potentials of big data and learning algorithms,the identification and analysis of unanticipated relationships and processes.

A probable tyrannosaurid track from the Upper Cretaceous of southern China

A large number of Upper Cretaceous(Maastrichtian)dinosaur skeletal fossils have been found in the Nanxiong Basin and adjacent Ganzhou area,including those of theropods,sauropods and hadrosaurids.However,known dinosaur ichnoassemblages from the Nanxiong Basin partly indicate a different fauna,with dominating large-and medium-sized ornithopods,theropods,and pterosaurs(1,2)This is one of many known examples where trace and body fossil assemblages from the same formation or geologically discrete region show a different composition.Palecological and paleobiogeographical analyses therefore should consider data from both,before any conclusions can be drawn.Formations can be classified according to the relative degree of similarity or congruity(or difference/incongruity)between trace and body fossils into the 5 categories proposed by Lockley[3].