Porous coordination network materials, also known as Metal-organic Frameworks (MOFs), are at the cutting edge of molecular materials science. DEFNET, “DEFect NETwork materials science and engineering”, is the first European Training Network (ETN) at the intersection of chemistry, physics and engineering aimed at structural and functional complexity of MOFs. It provides a unique interdisciplinary training platform for early stage researchers and combines the expertise of the academic and the non-academic sector for fundamental development and industrial application and technology transfer aspects. The research and the training program in materials synthesis, characterization, computational modelling and application is accomplished in a coordinated effort involving 8 academic and 8 industrial partners from 6 European countries. DEFNET will particularly investigate defects, disorder and correlated phenomena in MOFs and related materials. The understanding and the intentional modification of defect structures of porous coordination networks is essential for advanced controlling their properties in catalysis, gas capture and separation beyond existing materials limitations. Benchmarking will be done against selected zeolite materials, which are very well established for large scale industrial applications. It is anticipated that superior functionalities of defect engineered MOFs will be identified which cannot be achieved by employing other porous materials.