Journal Article R-134a adsorption refrigeration Research Support, Non-U.S. Gov't bottom-up covalent triazine-based frameworks downsizing efficient reduction methods flexible transparent conductive films graphene heat transformation heteroatom heteroatoms lithium-ion battery metal-free metal-organic frameworks oxygen reduction reaction patterned rGO films pore size pore size effect porous organic networks reduced graphene oxide silicon anode supercapacitors surface-controlled lithium storage