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• Defect types of solid materials are classified. • The forms of various defects in graphynes are given. • The application of different defect types of graphynes are introduced. • The opportunities and challenges of defective graphynes are discussed. Graphynes have great application potential in energy storage and conversion. However, due to the limitation of specific surface area and active site, their energy storage capacity and catalytic efficiency are expected to be further improved. Defect engineering is a complex technique that can alter the geometry and chemical environment of a subject via introducing defects. Defects such as vacancy and heteroatom can expose a lot of coordination unsaturated sites, change the charge distribution around the carbon atom and improve graphynes cycle stability, thus markedly promoting the catalytic activity and significantly optimizing the battery energy storage of graphynes. In this paper, the research progress of defect engineering of graphynes in energy storage, electrocatalysis and photocatalysis is reviewed. Firstly, the classification of defects in solid materials and the forms of various defects in graphynes are given. Secondly, the application of different defect types, such as elemental doping, vacancy, single-atom catalyst and heterojunction on graphynes for energy storage, catalysis and solar cells are introduced. Finally, the opportunities and challenges for the future research on defective graphynes are discussed. [ABSTRACT FROM AUTHOR]

• Bio-inspired hybrid materials as photocatalysts. • Biopolymers as templates, supports, immobilisation substrates for photocatalysts. • Enzymes, peptides, proteins based materials-coupling biodegradation. • Greener synthesis of metal based photocatalysts-opportunities and developments. • Photocatalytic degradation of various pollutants by biomaterials-based catalysts. New materials tend to revolutionize scientific community and human race on a larger level. Scientists worldwide have not just been working on some wondrous materials with superior properties but have progressively focused on greener bio-inspired or bio-compatible materials for sustainable development. An increasing number of researchers have been working on using biomaterials as a part of photocatalysts for stability, bio-compatibility, generation of more reactive oxygen species and enhancement of optical absorption. In this review we have focussed on photocatalysts based on biopolymers, biochar, carbons, enzymes and proteins. This review presents various types of bio-inspired nanomaterials and their use as sustainable photocatalysts for degrading various venomous pollutants. The effect of pyrolysis temperature, temperature gradient, feedstock and synthetic route of biochar and carbon on the properties and final performance of derived photocatalysts has also been discussed. The increase in surface area, active adsorption sites, electron shuttling & reservoir properties, high visible absorption, charge separation and biocompatibility have also been elaborated. As far as photocatalytic performance is considered such bio-based photocatalysts are often questioned for their stability under such conditions and poor activity as compared to pure metal-based catalysts. These limitations can be overcome by choice of materials, modifications, new designing routes and coupling of biological methods and photocatalysis for removal of pollutants even from water from waste water treatment plants. Suitable modification to biomolecules as functionalisation has been reported for better adsorption of pollutants. The role of biomaterials in generation of reactive oxygen species, recombination suppression, interactions with pollutants, optical absorption, separation of charge carriers, shuttling and electron flow has also been elaborately explained. The concerns, challenges and future opportunities are also included in this review. [ABSTRACT FROM AUTHOR]