Abstract:

With the fast advancement of human modernization and rapid development of social economy, traditional energy consumption has been enormously increased and climate change has therefore become a very challenging issue for the human being. The development of modern industry, especially the chemical industry, has brought not only convenience to people, but also unprecedented destruction to the ecological environment closely related to human life. Energy and environmental issues have become a global challenge for us today. In order to better deal with the challenges and protect our living homeland, the majority of researchers are constantly seeking and exploring new materials and technologies which are environmentally friendly and can be used efficiently, aiming to solve increasingly serious environmental problems. In current stage, environmental materials and technologies have received ever-increasing attention and are developing rapidly.

Environmental materials, as the name implies, are materials designed and developed for environmental issues. The key issue of environmental problems is environmental pollution. At present, the widely concerned pollutants include gas pollutants, persistent organic pollutants (POPs), and heavy metals. At the same time, with drastic development of nuclear energy industry in the past two decades in China, radioactive pollutants have also received increasing attention. Separation and removal of these pollutants from environment by certain means is an effective and common method for environmental pollution control. Therefore, the key for solving environmental problems is to develop materials and technologies that can effectively remove environmental pollutants. Plenty of versatile materials for specific contaminant removals have been reported over the past few decades. These materials come in a wide variety of functions, with varying structures and performance. Most concerned materials include traditional molecular sieves^[1], mineral materials^[2], carbon materials such as graphene and carbon nanotubes^[3], polymer based materials such as resins^[4], metal organic frameworks (MOFs)^[5] and covalent organic frameworks (COFs)^[6]. Among these materials, inorganic materials have broad application prospects in the removal and separation of environmental pollutants due to their stability, low cost and environmental friendliness. In particular, inorganic nanoporous materials have become favorable in recent years. The nanometer size makes nanomaterials not only have quantum size effect, but also possess larger specific surface area and more surface atoms compared to other common materials, thus exhibiting stronger adsorption ability and better dispersibility in aqueous solution. In addition, the porosity of materials greatly enhances the specific surface area and correspondingly increases the contact opportunity between the material and contaminant. Meanwhile, it also improves the diffusion and transportation of contaminants inside the material, elevating the adsorption kinetics. Metal nanomaterials, metal oxide nanomaterials, mineral materials, etc. are typical representatives of inorganic nanomaterial family.

Based on the published works, many efforts in the field of inorganic environmental materials focused on improving the removal efficiency and selectivity toward one or more target pollutants. Inorganic materials have higher stability than organic materials, but possess low removal capacity and poor selectivity, due to lacking of active functional groups on the surface. Functionalization of inorganic materials should be a reasonable approach to overcome this drawback. It is well known that functional groups with strong binding or coordination ability to the target contaminant decorated on the surface of material by physical or chemical means can greatly improve the adsorption performance of inorganic materials^[7]. Moreover, besides modifying the specific recognition group on the surface of the material^[8], adjusting the pore structure of material and physically screening contaminants by the size effect^[9] are always common and effective. It is also promising to combine size effects, bonding and electrostatic interactions by means of molecular imprinting or composition^[10]. Besides, developing inorganic environmental materials used under harsh conditions^[11], such as high acid, high alkali, and high temperature, is becoming a research hot topic in recent years.

In all, after decades of development, researches on inorganic environmental materials have made significant progress, whereas most of materials are still not satisfactory for industrial applications. In order to better solve the increasingly serious environmental problems, it is still necessary for the material researchers to overcome difficulties and make continuous efforts.