Thermochemical and electrochemical CO2 reduction by a cyclophosphazene and triazine based inorganic–organic hybrid nanoporous metal-free catalyst

•Heterogeneous catalyst CTHM-2 shows excellent efficiency towards CO2 conversion.•100 % conversion of CO2 into cyclic and polycarbonate by thermochemical approach.•79 % retention ability of the product even after 5 consecutive cycles.•Electrochemical conversion of CO2 to methanol with 66.68 % Faradic efficiency.